Claude Haiku 5.5

I'm planning a single-file Snake game in vanilla JS on canvas, checking it against the constraints: one fenced code block with nothing around it, everything inline, no storage, no alerts or popups, and layout that works at 1280×800 and shrinks to 375px without a horizontal scrollbar. It also needs something meaningful on screen right away.

I'm going through the remaining requirements: a 20×20-or-larger centered grid, arrow keys and WASD with an input queue that never allows a reverse, food that grows the snake and never spawns on it, and game over with restart and pause controls. I'm also keeping in mind the polish goals, like smooth interpolation, a distinct head, and a particle burst on eating.

I'm settling on a 24×24 grid for good play at both sizes, and I'm working through the rendering approach: the snake advances on a fixed tick, with each segment interpolated from its previous to its current position using requestAnimationFrame.

Still working out how the snake's body interpolates when it grows, since the segment count changes between ticks.

I'm working out how each body segment maps from the old positions to the new ones after a growth step: the head comes from the stepped-forward position, and every other segment shifts one slot toward the tail, so I can interpolate each one from its previous index.

I'm working out how the body segments should interpolate, since each one moves into the cell of the segment in front of it while the head steps forward. I'm weighing whether the head should interpolate from its old position or whether the body needs a different mapping, so the rendering doesn't snap.

I'm working out the body mapping for a step without growth: the head moves into the new cell, and each following segment takes the cell of the one in front of it, so its old position is the previous index in the old body.

I'm checking the body mapping for interpolation: the head moves from its old cell into the new one, and each following segment takes the cell that the segment in front of it occupied before the step. That means the segment at index 1 slides into the old head position, so I need to see what that does to the interpolation before I settle on it.

I'm tracing the body mapping through entities instead of indices: the head moves into the new cell, and the old head's entity becomes index 1 without moving, so I need to separate what each physical segment does from what its index is.

I'm tracing the entities through a step without growth: the head moves into the new cell, and every other segment moves into the cell the one before it just vacated. So each segment's own old position is the starting point for its slide toward the old position of the segment in front of it.

For a grown segment, I'm treating its previous position as the old tail cell, since that cell stays occupied and the new segment appears there rather than sliding in from nowhere.

For a grown segment the cell it started in is the old tail cell, so the render clamps the lookup to the last previous position and the new segment stays put. Without growth, the tail entity is removed on the step, so the body mapping has to handle that case separately.

I'm checking that the index-based interpolation still holds when the length stays the same: the tail entity slides into the cell ahead of it, so the segment count doesn't change and nothing needs special handling.

I'm settling the array version of this: when not growing, the new body is the new head plus the old body minus its last element, and when growing it keeps the whole old body. Either way index k lines up with the same physical segment, so the previous position for each index can come straight from the old body array.

Now I'm checking the rendering rule for the head and the new tail: each index interpolates from its previous position, clamped to the last old one, so the grown segment stays put and the head slides cleanly from old to new.

I'm deciding what happens at the wall: the step checks whether the next head cell is off-grid or hits the body, and if so the game ends and the snake freezes rather than animating into the wall. I'm also planning to smooth the head's facing by easing a `headAngle` toward the target direction, instead of snapping the eyes on each key press.

Next I'm settling the head's smooth turn: easing its angle toward the target direction along the shortest arc. Then I'm moving on to the body, where I'm weighing how to draw the segments as one continuous shape, with a color gradient from head to tail and joins between neighboring segments so there are no visible gaps.

I'm now drawing the snake's body as a shape with a darker outline stroked along the whole interpolated path, then a lighter color stroke on top, with round caps so the joints stay smooth.

Still working out the body rendering: I'm drawing each segment as a thick rounded line in a color that shifts from tail to head, over a darker outline, and I'm considering a faint highlight stripe along the middle for a glossier look.

I'm considering a glossy highlight: a faint white stroke along the whole body path. For the gradient, a single linear gradient from head to tail would be simple, but it ignores the snake's curves, so I'm leaning toward drawing each segment in its own color.

Still working on the body rendering: I'm drawing each segment as a thick rounded line in a color that shifts from tail to head, with the stroke width kept fixed. I'm avoiding a per-segment shadow blur because it would be too costly across a long snake.

I'm settling the body's look: a bright lime-green head and a teal gradient fading toward the tail, drawn over a deep navy background with faint grid lines. I'm weighing a darker outline pass against a simpler glossy highlight, leaning toward skipping the outline to keep the draw count down.

I'm planning the rest of the visual polish: a little flicking tongue on the head, a glowing red-pink food orb that pulses, and particles that burst out of the food when it gets eaten. I'll also add a small floating "+10" score text that rises and fades, and I'm weighing whether to add a screen shake on game over.

I'm sizing the canvas to fit the window: the board is the smaller of the viewport width minus padding, the viewport height minus the header, and 640px, with the backing store scaled by devicePixelRatio for crisp edges. I'm working out the cell size from that CSS width across a 24×24 grid, and I'm keeping a fractional cell size acceptable since drawing happens in scaled coordinates.

Next I'm laying out the page: a full-viewport dark background with a faint radial glow, the content centered in a column. The HUD sits above the board with the title on the left and the score and best stats on the right, and I'm making the container the same width as the board so everything lines up.

I'm settling on skipping audio: an AudioContext can't start without a user gesture and would log a console warning, so I'll leave sound out entirely. I'm also planning a hint bar under the board with the controls and a short prompt telling the player how to begin.

I'm settling the start message: rather than covering the board with a full overlay, I'll put a translucent pill-style prompt over the middle of the board so the AI demo keeps playing visibly underneath.

I'm weighing a card-style start message over the board with a light dim so the demo snake stays visible underneath, rather than a full opaque overlay that would hide the action.

I'm deciding whether the demo's score should show on the HUD, and I'm leaning toward letting the counter run during the demo but keeping the best score tied only to games the player actually plays. The score then resets to zero when the user starts.

I'm still weighing whether the HUD should show the demo's score while the AI plays, leaning toward showing it so the numbers match what's on the board, while BEST only tracks games the player actually plays.

I'm weighing whether the HUD should show the demo's score: I'd keep the demo's score visible with a small "DEMO" tag on the board, and leave BEST untouched so it only reflects games the player actually plays.

I'm thinking about how the first screenshot will look, since the AI snake will probably eat a piece of food within a few seconds and the particles will be visible. The HUD will show a score like 10 or 20 from the demo, while BEST stays at zero until the player actually plays, so I'll keep those two separate. Next I need to work out the AI for the demo.

I'm settling the demo AI: a greedy approach that runs a BFS from the head toward the food, treating the body as obstacles except the tail tip, and takes the first step of that shortest path when it's safe. If there's no path, I'll fall back to whichever safe move keeps the most open space reachable via flood fill.

I'm settling the demo's end-of-game behavior: if the AI crashes, I'll skip the game-over overlay entirely, flash briefly, and start a fresh demo after a short pause, keeping the start message visible the whole time. The AI itself shouldn't hit walls, and the demo's speed will match the player's.

Next I'm writing the demo AI's move selection: check which of the four directions are legal, treating the body as blocked except the tail, and run a BFS from the head toward the food.

I'm working out the demo AI's scoring for each candidate move: if the food is reachable from that cell after simulating the new body, I'll weigh the distance to food, and I'll also count the reachable free area from that cell, favoring moves that still reach the tail.

I'm settling the demo AI's move choice: for each legal candidate, I'll check whether the food is still reachable and whether enough open space remains to avoid trapping the snake, preferring the closest food path among safe options. If no candidate passes that, I'll fall back to whichever move leaves the most room. Then I'll turn to the input handling, where the first keypress should start the real game.

I'm settling the input handling: arrow keys and WASD set the direction, and Space or Enter restarts after a game over. P pauses and resumes during play, and the first key press or click in demo mode starts the real game.

I'm leaning toward clicking the canvas to resume during pause and to restart after a game over, though the spec only names Space or Enter for restart, so that's an extra I can keep since it's harmless.

I'm thinking about adding a restart button to the game over overlay for mouse users. A focused button could cause a double restart if Space or Enter also fires our keydown handler, so I'll guard the restart so it only runs when the state is game over.

I'm weighing the restart controls: the overlay won't carry any buttons, since a focused button could double-fire with the Space or Enter handler. Instead, clicking the canvas or pressing Space or Enter will restart after a game over.

I'm settling the input queue: a few direction presses can stack up, and each one is checked against the last direction already planned rather than the snake's current heading. That way a quick Up then Left gets both moves honored over two ticks, while a reversal is still rejected.

I'm settling the input queue details: a same-direction press can be skipped, since it wouldn't change anything. Whether it gets queued or dropped, a press that reverses onto the snake's own body is rejected.

I'm checking the input queue against the last planned direction rather than the current heading. A quick Up then Right gets queued and both moves are honored, and a press that would reverse the snake, like Left while moving right, gets rejected.

I'm checking that the reversal guard holds up: the head moves along the last planned direction, so the next planned move can never be the exact opposite of the one before it, which means the snake can't fold back into its own neck. I still need to work out what happens when the queue is empty and the current direction is all that's left to compare against.

I'm settling the input timing: directions get consumed one per tick, with the queue capped at three presses so it can't lag behind. I'm also weighing the snake's speed, starting around 8.5 cells per second and rising a little with each food eaten.

I'm settling the speed curve so the snake gets a little faster with each food eaten, with the interval floored so it never gets unplayable. Then I'll tie the loop to requestAnimationFrame and accumulate elapsed time, stepping the game for each full interval and using the leftover fraction to interpolate drawing. I still need to make sure the accumulator doesn't build up while the game is paused.

I'm finishing the death handling: when a step hits a wall or the body, the state goes to game over without moving the head into the bad cell, so the snake stays where it last was valid. I'm weighing a short death effect, a red flash on the head with a small burst and a brief board shake, before the overlay appears after about 400ms.

I'm working out how the self-collision check treats the tail: when the snake isn't growing, the tail moves away this tick, so the head can safely enter the cell the tail occupies. If the snake is about to grow, the tail stays put, so entering its cell counts as a collision.

I'm checking the self-collision rule: the tail vacates its cell when the snake isn't growing, so the head can enter it safely, but if food is about to be eaten the tail stays and that cell counts as a collision. I still need to handle the edge case where every cell is filled, which would be a win rather than a loss.

Still working out the particle effects on eating: a burst of about 22 particles from the food cell with varied angles and speeds, a glow from additive blending, and an expanding ring plus a rising "+10" label. Next I'll make the food itself a pulsing red-pink apple with a radial glow.

I'm drawing the food as a pulsing apple-like orb with a radial highlight, a soft halo behind it, and a small green leaf. For the snake's head I'm using a larger, brighter circle than the body segments, with two eyes set forward at about ±40° from the direction of travel, and their pupils shifted toward where it's heading.

Still working out how the eyes and tongue sit on the head: placing them forward and to either side, with pupils nudged toward the direction of travel. Adding a flickering forked tongue on a timer.

Now I'm settling the head's appearance: the eyes sit forward of center with their pupils nudged the same way, and I'm thinking the body should taper from a thicker neck to a thinner tail, each segment with its own width and color shifting from head to tail. Drawing tail to head so the head stays on top.

I'm working out the draw order for the tapered body: each segment's width should shrink toward the tail, so drawing from tail to head lets the thicker segments near the head overlap the thinner ones' round caps.

I'm working out the body's outline: stroking each segment twice, once darker and wider, would mean up to about 1,150 strokes per frame near the end of a long snake. I'm weighing a single path along all the points instead, stroked once for the outline and once for the fill.

I'm dropping the separate outline pass and drawing the body as one stroke per segment, each with its own color and width. Then a single polyline along all the points gets a faint highlight on top.

Next I'm weighing a banded pattern over the gradient: alternating slightly darker segments along the body would read more like scales than a glossy tube, and it costs nothing extra since it's just a parity check on the color.

Still working out how the body is drawn: each segment's width should be set from its position along the snake, and the head's radius relative to the cell size.

I'm settling the head's shape: a diameter just under one cell, with the neck around 0.80 cell and the tail about 0.42. The head should stand out through its color and eyes rather than size alone, and I'm considering an elongated capsule outline along the direction of travel instead of a plain circle.

I'm sizing the head as a slightly elongated oval facing forward, with the eyes placed toward the front and their pupils nudged in the direction of travel. The head's rotation comes from a smoothed angle, and its position from the interpolated first point.

I'm deciding the eyes turn into X marks when the game ends, which is cheap to draw, and I'm settling the board's look with a subtle grid, a gradient background, and a vignette.

I'm laying out the board frame as a rounded container with a glow and a subtle border, with the canvas filling it. For performance, I'm pre-rendering the background (grid and gradient) to an offscreen canvas at the right resolution and blitting it each frame.

Still working out the responsive layout: the board should be the smaller of the available width minus padding and the height left after the header and footer, capped around 620px so it fits 1280×800.

I'm sizing the board as the largest square that fits the remaining width and height, capped at about 620px, and I'm thinking about how a landscape phone would look with the HUD moved to the side.

I'm settling the overall layout: the board centered with a score and best-score chips above it and control hints below, all stacking down to 375px. I'm also picking a restrained wordmark for the title, and I'm planning the start, pause, game-over and victory overlays as DOM elements over the board, deciding how clicks on them should reach the game.

I'm weighing how clicks reach the game: the board wrapper takes clicks so the overlays don't block them, while keys are caught on the window, since the iframe only passes keyboard input once it's been clicked. I'm settling the start overlay to read "SNAKE" with the prompt to click or press a key.

I'm settling the start, pause, game-over and victory overlays as text over the board, and I'm writing out their wording: a start prompt asking for a click or key press, the steering and pause hints, the paused and resume lines, and the game-over screen showing score and best with a restart prompt. I'm also weighing a small "DEMO" pill in the board corner during the attract mode.

I'm weighing a centered card for the start message, but it would cover the middle of the board where the snake usually moves. A pill at the bottom edge keeps the action visible while still reading clearly on the first paint.

I'm weighing a semi-transparent start overlay across the whole board with the text card on top, so the snake stays visible behind it. I'm also keeping the card compact, around 260×120px, so most of the playfield remains uncovered.

I'm sizing the board from the viewport: the width minus padding, and the height left after the header and footer, capped around 620px so it fits 1280×800 and still works on a 375px phone.

Still writing the page's CSS: root colour variables, a dark gradient body, and box sizing reset.

Still writing the page's CSS, setting up the body's background, flex centering, padding and text selection behaviour.

I'm sizing the header so the title and the two stat chips still fit within the board width, which means on a 343px phone the layout has to hold together rather than overflow.

Still writing the sizing logic: the board takes the smaller of the viewport width minus padding and the height left after the header and footer, capped around 620px, with the header and footer heights measured so the layout still fits.

Still writing the layout code: the board's size is set from the free height after the header and footer, with the canvas backing scaled to the device pixel ratio. I'm also planning the grid as 24 by 24 cells, with the background pre-rendered to an offscreen canvas.

Writing the game state variables and the Snake data setup...

Setting the snake's growth on a food pickup: the head moving onto the food skips the tail pop that step, so the snake grows immediately and no pending counter is needed.

Still working on the collision check: the snake's own body is tested for hits, except the tail, which is about to move away unless the head is eating food.

Still working out the movement step: the head moves into the next cell, the tail only drops when the snake didn't eat, and the self-collision check skips the tail unless food is being eaten. I'm also deciding how queued direction changes get validated against the last planned direction, not just the current one.

I'm settling how input gets queued: a key press is ignored if it matches the planned direction or reverses it, and otherwise goes onto a queue of up to three moves. Two quick presses, like Up then Right or Down then Left, both stay valid because each is checked against the last planned direction rather than the current one.

I'm checking the direction queue: a second key press is validated against the last planned direction, so Down then Left both go through, while a press that reverses the planned direction, like Down after Up, gets dropped. Next I'll look at what happens when the snake dies.

I'm handling the death case: the snake's body stays where it was, so the previous positions are copied before the move is attempted and nothing interpolates on a crash. In demo mode the game drops back to the attract loop after a short delay instead of showing the overlay.

Writing the input handler now: arrow keys and WASD map to directions, Space or Enter restarts from the over or won states and starts play from demo, and P toggles pause.

Handling the remaining input details: holding a key sends repeated keydown events, but a repeated direction key just matches the planned direction and gets ignored. Enter repeating after a game over is harmless too, since the restart no-ops once play has begun.

I'm checking the key handling now: repeated P, Space and Enter presses get ignored so holding them doesn't toggle pause or restart over and over. From the demo, any key starts a fresh game and a direction key is then applied against the reset rightward heading, so a reverse press is still dropped.

Click handling on the board wrapper comes next: a click in demo mode starts a game, and a click while paused resumes. A click in the over or won state restarts, but only once the overlay has appeared, so a stray click during the death animation doesn't trigger a restart.

Next I'm settling the pause behaviour: P toggles between playing and paused, but only from those two states, and pressing it in demo mode just starts a game instead. I'm also clamping the frame delta to about 50ms so a backgrounded tab doesn't cause a huge jump when it comes back, and I'm weighing whether to auto-pause when the window loses focus.

Next I'm getting the demo mode loop ready: each tick the AI picks a direction and feeds it into the same queue as player input. I'm also planning a visibility check so the game pauses if the tab gets hidden mid-play.

I'm picking the demo direction each tick by clearing the queue and choosing from the current heading, since the queue is normally empty in demo. When the AI's snake dies, I'll reset to a fresh demo game after about 600ms, and the HUD will just show the demo score starting again from zero.

I'm deciding how the HUD labels things: score shows the current score, best shows the session best, and a small "DEMO" tag appears on the board while the attract mode is running. Best only gets recorded at game over when play was active, and I'm also weighing whether to update it live during play so it climbs as the score passes it.

Now I'm adding particle, ring, and popup effects, with the eating burst spawning particles at the food cell's center.

Now I'm adding the particle burst, the ring, and the "+10" popup when the snake eats, and a small screen shake on death that fades out over about 300ms. Then I'm laying out the per-frame draw order: the background first, then the food, then the snake, with the particles and effects on top.

Next I'm working out the draw order and interpolation: each frame I compute t from the accumulator over the step interval, so the snake glides between cells. When paused or dead, the snake stays where it is, since the previous body was set to match the current one.

Next I'm working out how the interpolated body positions are computed each frame, looping over the body segments and blending each one between its previous and current cell with the interpolation factor.

Still writing the interpolation code for the eyes and tongue...

Still working out the tongue shape and the body palette, with the head in a lighter mint and the body shading into teal.

Still working out the head and body colours, with the head a pale mint fading to a brighter edge and the body shading from light teal near the head down to a darker tone at the tail.

I'm weighing a drop shadow under the snake, which would add depth, but drawing a dark copy of the whole body offset down and right doubles the stroke count. At up to around 1,150 strokes a frame, it should still be fine on desktop but may be tight on low-end phones, so I'm considering limiting it to the head or skipping it.

Still working out the body rendering, and I'm weighing a shadow pass against performance. Drawing the food next with a pulsing glow.

Next I'm finishing the visual details: the food's leaf and stem, a lighter glow for particles and rings, the "+10" popup that rises and fades, and the expanding ring on eating. Last, I'm building the background once offscreen as a dark gradient with faint grid lines and a subtle checker.

I'm settling the overlay: the overlays won't block clicks, so the board wrapper catches them, and the game-over card shows the score and best with a restart hint.

Now I'm working out the AI for demo mode, starting with an occupancy grid that marks cells blocked by the snake, so the chooser can avoid running into itself.

Still writing the AI's occupancy grid and candidate checks...

Still working out the AI's blocked-cell check: the new head cell gets marked as occupied for the next step, while the tail is treated as free unless the snake is about to grow.

Now I'm working out the candidate moves: each one that isn't blocked gets a BFS distance to the food, measured across the grid with the snake's body treated as walls.

I'm checking each candidate move by how much open space it leaves and whether a path to the tail stays reachable. Where a move reaches the food with enough room, I'd take the shortest route to it; otherwise I'd prefer the option that keeps the tail in reach.

I'm settling how the AI decides whether a region is big enough: the free area around the candidate has to hold the snake, and the tail cell counts as free because it will move. If the tail is still reachable from a move, that's a safer fallback, and when the snake is very long the region might be small enough that this fallback takes over. I also need a plan for when the food sits in a region the candidate can't reach.

Still writing the BFS and flood-fill helpers for the AI, with reusable buffers and a visit stamp so each call doesn't have to clear the grid.

Still writing the flood-fill helper, counting reachable cells and tracking the distance to the food.

Still writing the flood-fill helper, checking whether the tail cell gets visited so the AI knows if a path back to it exists.

Still writing the flood-fill helper, checking the visit stamp so each call starts clean, and I'm keeping the full count instead of stopping early at the target.

Still writing the food spawn: I'm building an occupancy grid from the snake's body, collecting the free cells, and picking one at random.

Still working out the start state and the reset function, with the snake centred and heading right.

Still writing the Snake game's main loop, setting the frame timing up to step the simulation.

Still writing the game loop's update function, which advances the simulation on a fixed interval and updates the effects each frame.

Still working out the AI's move choice: each tick it picks a direction and queues it, so the step function applies that choice before moving.

Still working out the demo speed: I'm setting the snake's tick interval to shrink as it eats, with a floor so it never gets too fast, and keeping demo mode at a fixed pace so it looks lively.

Next I'm working out the demo timing: I'll keep the same speed formula as normal play, or use a fixed interval around 115ms so demo mode looks lively. The HUD only gets updated when the score changes, not every frame. Then I'm starting on the death handling, where a burst and screen shake fire on the head and demo mode resets after a short pause.

I'm setting the death handling for demo mode: a short pause after the snake dies, then the demo restarts. For the player, the game-over overlay waits about 450ms before it appears, so I'm counting that down in the update loop.

I'm wrapping up the death and win handling: the player's game-over overlay appears after a short frame-based delay, the screen shake fades out over time, and if spawning food finds no free cell after eating, the game switches to a board-cleared state.

Still writing the overlay markup: a start card with a demo kicker, the title, and a prompt to click or press a key.

Still writing the overlay markup: the header stats, the start card, and the pause, game-over, and win overlays.

Still writing the overlay markup: the header with the score and best stats, the footer key hints, and then the CSS for the board and cards.

Still writing the stylesheet: the colour variables, box sizing, and a flex body that fills the viewport.

Still writing the stylesheet: the body is centred with flex, sized with padding, and styled with a dark font and layered background gradients.

Still writing the stylesheet: the app wrapper, header row, and brand styling with a glowing logo.

Still writing the stats styles: a small chip with a tiny uppercase label over a bold number, with the best-score chip possibly getting an accent colour and a short pulse when the value changes.

Still writing the board styles: the canvas fills the rounded board container, which gets a soft glow.

Still writing the tag styles: a small rounded pill in the top-left corner with a blinking accent dot.

Still writing the overlay styles: each overlay is absolutely positioned and hidden by default, and a show class fades it in.

Still writing the overlay styles: the title and big score text are being set up next, with a red variant for the game-over heading.

Still writing the keyboard hint styles: the kbd keycaps get a monospace font with a raised bottom border, and the footer hints are a wrapping flex row that stops each hint from breaking across lines.

Still writing the layout sizing function, working out the board's dimensions from the viewport width and height, minus the header and footer heights.

Still working out the layout sizing: the board gets a size from the viewport width and height, minus the header and footer, capped at a maximum and floored at a minimum.

Still working out the layout sizing: the board caps at 640px, and I'm checking that it still fits vertically at 1280×800 once the header, hints, and padding are counted.

Still writing the render function: setting the canvas transform for the device pixel ratio and working out the screen shake offset.

Still working on the render function: I'm keeping the background static and only applying the screen shake offset to the board contents.

Still writing the render function: I'm applying the shake as a canvas-level translate after the background is drawn, and the interpolation position is clamped to one at most, so paused and dead states hold their position.

Still writing the food drawing: a radial glow around each apple cell that pulses slightly over time.

Still writing the food drawing: the apple's stem and leaf are next, with the stroke width set relative to the cell size.

Still writing the apple's stem and leaf, with the stroke width scaled to the cell size and the leaf as a small green ellipse beside it.

Still working on the snake's rendering: I'm interpolating each segment's pixel position between the previous and current grid cells, using a preallocated array so nothing gets reallocated every frame.

Still writing the snake's segment drawing: each body segment gets a stroke width that tapers from head to tail, and the colour comes from its position along the body.

Still writing the snake's segment outlines, with each stroke drawn between neighbouring segments and the caps overlapping at the joints.

Still writing the snake's segment outlines, and I'm checking how the round caps overlap at the joints.

Still writing the snake's body colours: each segment's shade fades from head to tail, with a subtle alternating band.

Still writing the snake's head: a radial gradient fills the ellipse, with a light highlight at its centre, and the head is rotated to match its heading.

Still writing the snake's head: the eyes are next, placed forward of the centre and offset to either side, sized from the cell.

Still writing the eyes: a pair of white eyes with dark pupils and small glints, set to either side of the head.

Still writing the eye details: the dead state swaps the eyes for X marks, and the tongue flicks out from the front of the head while the snake is alive.

Still writing the snake's tongue flick, where the tongue length scales with a sine curve over the flick phase.

Still writing the head rotation: the head angle eases toward the current heading each frame, with the difference wrapped so it turns the short way round.

Still writing the particle burst: each spark gets a random angle and speed, a lifetime, a size, and a colour picked from the list.

Still writing the particle update: each spark ages, slows with drag, and gets pulled down by a little gravity each frame.

Still writing the particle physics: drag slows each spark exponentially and gravity pulls it down a little every frame. Now I'm drawing the particles with alpha and size fading over their lifetime, and the expanding rings with a shrinking line width.

Still writing the overlay logic: a function that syncs which overlay is visible based on the game phase, with the demo phase showing the start screen and the DEMO tag.

Still writing the overlay logic: a setOverlay helper will toggle the show class on each overlay by name, and the game-over overlay is only revealed once its death timer runs out.

I'm working out the death overlay: filling in the final score and best, and showing a "New best!" badge only if the best rose during this run, which I'll track by recording the best value when the run starts.

I'm deciding how the pause controls should behave: P toggles pause, and I'm weighing whether direction keys pressed while paused should be ignored, or queued to apply on resume.

Still working on the particle system, and I'm switching particle positions to cell units so they stay correct when the window resizes. Velocities will be in cells per second, and I'll convert to pixels only when drawing.

Still writing the particle system, switching the physics to cell units with velocities around 2 to 6.5 cells per second, a gravity of about 5, and exponential drag.

Still writing the keyboard handler: each arrow key or WASD letter maps to a direction, and the default is prevented so the page doesn't scroll.

Still writing the keyboard handler: when a direction key comes in, I'm starting a game if one isn't running and queueing the turn while playing. Space and Enter start or restart a game once the death timer has finished, and I'm about to handle the P key for pausing.

Still writing the keyboard handler: the P key toggles pause, but when the game is still in its demo phase it starts a game instead.

Still writing the game loop: a `phaseTimer` counts down each frame, and once it runs out the death overlay appears or the demo restarts.

Still writing the keyboard and phase handling: when the death timer runs out, the game-over overlay gets set up, and when a demo death timer runs out the demo restarts.

Still writing the death handling: on a player death the overlay waits out its short delay before showing, and the demo death restarts after a brief pause.

Still writing the step logic: the body is kept as a list of segment objects, and since they're never mutated, a shallow copy is enough to snapshot the previous positions for interpolation.

Still writing the step logic: the snake is blocked by a wall or by its own body, with the tail excluded from the body check unless the snake is growing.

Still writing the step logic: if the snake dies, the body stays where it is and the death handler runs. Otherwise a new head goes on the front, the tail comes off unless it ate, and eating calls the food handler.

Still writing the game-over flow: the overlay waits out a short delay, and the demo restarts itself after a brief pause. On eating, the score goes up and a new food spawns, with the win state kicking in if no free cells remain.

Still writing the death handling: the tag and overlays get refreshed, and in demo mode the game drops into a short pause before restarting. Next I'm setting up the reset routine that lays out a fresh snake in the middle of the board for whichever mode is starting.

Still writing the reset routine: the snake is laid out in the middle of the board, the food is placed, the score and timers are cleared, and the UI is synced for the chosen mode.

Still writing the syncUI helper: it picks the overlay for each phase and shows the DEMO tag during the demo, with the game-over overlay held back while its timer runs.

Still writing the timer logic: when the countdown on the game-over phase reaches zero, the final score gets filled in and the game-over overlay appears, and the demo-death timer restarts the demo.

Still working through the game loop: when the death timer runs out, the overlay appears, and in demo mode the game resets itself. I'm also wiring up the pause toggle, which flips between playing and paused and then refreshes the UI.

Still writing the click handling: pointerdown starts a game from the demo or a finished run, or resumes from pause. I'm also adding swipe support for touch, so a drag of more than about 24px sets the snake's direction from the dominant axis.

I'm settling the pointer handling: a short press on the board counts as a tap and runs the state action, while a drag of at least 24px counts as a swipe. Swipes will set the snake's direction, and in demo or game-over states they will also start a game. I'm also setting `touch-action: none` on the board so a swipe doesn't scroll the page, and I'm noting the overlay pointer edge case I still need to check.

Still writing the pointer handling: I'm adding a swipe path on the board, so a drag of at least 24px sets the direction from the dominant axis, and in demo mode it starts a game first. Anything shorter counts as a tap and runs the state action.

Still writing the queueDir helper: it checks the new direction against the last queued direction, or the current one if the queue is empty, so the snake can't reverse onto itself.

Still writing the queueDir helper: a new direction is dropped if it matches the last queued one or would reverse onto it, and the queue is capped so presses don't pile up.

Still writing the AI: I'm setting up the direction list and a flood-fill lookup table, and building the blocked-cell map for the snake's body as the AI picks its next move.

Still writing the AI: I'm evaluating each legal move by how close it brings the head to the food, with the tail cell treated as free since it will move away.

Still writing the AI: the blocked map is filled from the body, leaving the tail free, and for each legal move I'm flood-filling from the new head cell to see whether the food and the tail are reachable.

Still writing the AI's scoring: I'm weighing each candidate move by whether the food can be reached from it and how much room is left to keep moving, since the tail stays a safe target to follow in a loop.

Still writing the AI's scoring: each candidate gets ranked by whether the food is reachable from it and whether the tail is too, since a region that includes the tail means the snake can keep moving without being boxed in.

Still writing the AI scoring: a move that can reach both the food and the tail gets the top score, weighted by how close the food is. Moves that only reach the tail rank next, weighted by how much open space they keep.

Still writing the AI scoring: candidates are ranked by whether the food and the tail stay reachable, and the flood-fill check on the tail decides the rest.

Still working on the AI's scoring: the tail is left free in the blocked map, and I'm weighing whether a move that reaches the tail is safer than one that only reaches the food.

Still writing the background: I'm building an offscreen canvas for the board's backdrop, starting with a vertical gradient fill.

Still writing the background: I'm shading the gradient from a dark navy at the top to a deeper blue at the bottom, then adding a faint checkerboard tint and fine grid lines over the board.

Still writing the background: I'm finishing the vignette, a radial gradient that darkens the board's edges, and then drawing the grid lines as a single stroked path.

Still writing the HUD: the score and best values get written into their DOM elements, and each update gives the element a short bump animation.

Still writing the HUD: the bump animation only fires when a value changes, on eating or a new best, and the tag gets a show class so it fades in and out during the demo. I'm also laying out the game-over overlay, which shows a "GAME OVER" title and the final score with a "Score" label above it.

Still writing the overlays: the start screen shows a glowing "SNAKE" title, a pulsing prompt to click or press a key, and a small line about steering and pausing. The game-over and cleared screens show the score and best, and the pause screen just says how to resume.

Still writing the responsive header: I'm narrowing the stat chips and brand text on screens under 380px so the top row fits without overflowing the board.

Now I'm checking the responsive layout numbers: at 375px the app fits in about 343px, and the header stats still fit. I'm making sure nothing forces a horizontal scrollbar, and accepting a vertical one if the content runs long.

Now I'm checking the layout math: the app's width stays under the viewport minus the body padding, so nothing should push out a horizontal scrollbar. I'm also thinking about the demo timing: after load it starts right away, so at around three seconds the AI should have eaten a food or two and the score should be visible.

Now I'm wiring up the visibility handler so the game pauses when the tab is hidden.

Still wiring up the pause handling: when the tab is hidden during play, the game pauses, and I'm considering whether to pause on window blur as well.

Now I'm working out the autoPause helper, which handles the tab-hidden and window-blur cases so the game pauses in both.

Still writing the head: I'm giving it a gradient and eyes, plus a tongue, and adding a soft glow around it with a shadow only on that one shape, since that's cheap per frame.

Still writing the particles: when a food is eaten, I'm spawning a burst of about two dozen small sparks in a few pink, gold and white shades, each with a short random lifespan and size.

Still writing the particle effects: on eating, a ring and a "+10" popup appear at the food cell, and I'm working out the death burst and screen shake next.

Still writing the setup: I'm defining the grid size, the starting length, the demo speed and the input queue limit, plus the four direction vectors.

Still writing the setup and state: I'm creating the offscreen background canvas and grabbing the DOM handles for the HUD, the overlays and the final score labels, then starting the phase as demo.

Still writing the input handling: I'm adding a Space key guard so it doesn't scroll the page, then wiring the visibility change so the game pauses when the tab is hidden during play.

Still writing the layout: I'm sizing the board to fit the viewport width and the space left after the header and hints, capped at 640px, and setting the canvas backing scale from the device pixel ratio.

Still finishing the layout code: the app width gets set first so the header and hints measure correctly, then the board size comes from what's left of the viewport.

Still writing the layout: I'm measuring the header, hints and gaps so the board fills the space left in the viewport, capped at 640px.

Still writing the particle effects: I'm defining the spark colors, count and lifespan ranges for when food is eaten, plus the ring and "+10" popup that appear at the food cell.

Still writing the spawn logic: I'm building a list of free cells that aren't occupied by the snake, preferring ones at least four steps away from the head, and picking one at random.

Still writing the step logic: I'm setting up the demo's direction choice and the queued turn, then working out whether the next head cell hits a wall or eats the food.

Still writing the step logic: I'm checking whether the head hits a wall or its own body, letting the tail count as clear on a normal move, and if it dies I'm ending the run.

Still writing the eat handler: I'm capturing the food's position, bumping the eat count and score, and refreshing the best score only during play. I'm also working out how the speed should change as the snake grows, separately for the demo and the real run.

Still writing the eat handler: the demo keeps a fixed speed, and only a real run speeds up with each food. I'm placing the burst, ring and "+10" popup at the food cell, then spawning the next food, and ending the game if no free cell is left.

Now I'm settling the win case: if the board fills up, the run ends, and in the demo it should restart rather than show a "Board cleared" screen.

Still writing the death handler: I'm bursting sparks at the head, starting a screen shake, and sending the demo into a short restart pause, or a real run into its game-over state with the final score filled in.

Still writing the death handler: I'm setting the final score and best labels now, then defining a helper that spawns particle bursts from a set of options.

Still writing the overlay logic: I'm showing one overlay at a time, with the start screen during the demo, pause while paused, and game over once its timer runs out.

Still writing the overlay code: the won screen shows the final score, and I'm working out how the start overlay stays up during the demo.

Still writing the tap handler: a tap during the demo or the restart pause starts a new game, a tap while paused toggles pause back off, and a tap on the game-over or won screen starts another run.

Still writing the input handling: the swipe handler starts a game in demo mode and then queues the direction, but only while playing.

Still writing the frame update: I'm turning the head smoothly toward the current direction each frame, then advancing the game clock and stepping the snake whenever enough time has built up for the current interval.

Still writing the frame update: I'm finishing the step timing and the phase timer, then clearing the screen shake and updating the particle effects each frame.

Still writing the particle update: I'm applying drag and gravity to each spark, and removing any whose lifespan has run out.

Still writing the frame update: I'm working through the particle draw logic and how rings and popups age out each frame.

Still writing the render function: I'm resetting the transform to the device pixel ratio and drawing the cached background canvas across the full board, since its backing store is already scaled.

Still writing the render code: I'm cutting the shake offset by the remaining shake time and translating the canvas by a small random amount, which means the edges may briefly show uncovered strips.

Still writing the render code: I'm drawing the food, then the snake, then the effects on top of the shaken canvas, with the uncovered edge strips showing the board background.

Still writing the food drawing: I'm placing it at the cell center, pulsing its radius slightly, and adding a soft pink halo behind it.

Still writing the food drawing: I'm adding the curved stem and the small green leaf.

Still writing the food drawing: I'm filling the body with a radial gradient from pale pink to deep red, then adding a small white highlight near the upper left.

Still writing the snake drawing: I'm interpolating each segment's position between the previous and current step.

Still writing the snake drawing: I'm working out each body segment's width, tapering it from the head toward the tail.

Still writing the snake body: I'm drawing each segment as a line from one point to the next, with the width tapering from the head toward the tail.

Still working through the snake's body rendering: each new segment is positioned between the old and new step, and I'm checking how the tail's growth interpolates so the new segment doesn't pop in.

Checking the tail growth: at t=0 the new end segment has zero length, and as the old tail moves forward the gap opens up, so the body extends smoothly rather than popping in.

Writing the snake's head now: I'm positioning it at the first segment and rotating it to face the current direction, with a soft green glow behind it.

Still writing the head: I'm working out the tongue's flick timing so it only shows while the snake is alive.

Still writing the tongue: it flicks out during a short window of each cycle, with the tip splitting into a fork.

Still writing the eyes: I'm placing them above and below the center line, with the dead state drawing crossed strokes instead of plain circles.

Still writing the eyes: I'm drawing the dead state as crossed strokes, and for the living state a white sclera with a dark pupil offset toward the front.

Still writing the eyes: I'm finishing the highlight placement, and checking that the eyes sit on the head's rim where they'll look right.

Still writing the eye placement: I'm moving the eyes a little forward and settling the offsets, then turning to the effects drawing with its rings and additive blending.

Still writing the particle draw: I'm fading each particle's alpha as its life runs down.

Still writing the popup text: I'm fading each popup out as its life runs down and drifting it upward.

Still writing the frame loop: I'm setting up the last-frame timestamp that the update step uses to measure elapsed time.

Still writing the game loop: I'm computing the frame's elapsed time, clamping it to avoid large jumps, and then updating and rendering with the interpolation fraction.

Still working through the frame timing: I'm checking how the interpolation fraction behaves when the accumulator carries over, since the head moves one cell per tick and the rendered position blends between the old and new grid spots.

Still writing the Snake game's effects: I'm weighing whether the death state should bump the head forward into the wall, and settling on the simpler approach of leaving it as is. Next I'm setting up the flood-fill visit stamps for the AI, with a counter that increments on each call.

Still writing the flood fill: I'm setting up the visit marks and BFS queue arrays for the AI, and the flood function that tracks distance to the target cell.

Still writing the flood fill: I'm finishing the BFS loop that marks each neighbor as visited and records its distance, then returning the reachable count and the target's distance.

Still writing the AI: I'm marking the snake's body cells as blocked, then checking each of the four directions for the head, skipping the reverse direction and any move that leaves the board.

Still writing the AI: I'm running the flood fill from each candidate neighbor, then scoring it higher when it reaches food and keeps access to the tail.

Still writing the flood fill's tail check: I'm confirming that the tail cell counts as reachable after the flood, so a move onto it stays a legal choice.

I'm checking the flood fill's edge cases: a candidate food cell gives a distance of zero, and the AI only considers moves that aren't blocked or off the board, so none of them can end in an immediate collision. A dead-end move still scores a small value, just lower than the others.

Still writing the HTML layout: I'm setting up the header with the logo, the score and best-score stats, and the wrapping app container.

Still writing the HTML: I'm adding the start, pause, and game-over overlays on top of the canvas, each with its title and hint text.

Still writing the game-over overlay: a title, the final score, a best-score row with a "New best!" flag, and a restart hint. Then I'm adding the win overlay and the footer with the key hints.

Still writing the HTML: the best-score note and the "New best!" badge get toggled by class, and I'm settling the start overlay's gradient title and keeping its font size to around 34px so it doesn't crowd the canvas.

Still writing the HTML: I'm working out the start card's wording, weighing whether to show a snake icon, and settling on a kicker line with the title and a short prompt, since the header already carries the brand.

I'm settling the start card's wording: a small "READY" kicker, the message to click or press a key to start, and a sub-line about arrows or WASD and pausing with P. The header keeps the SNAKE brand so the card doesn't repeat it.

Still writing the HTML overlays: the game-over card gets its red title, score, best-score row with the "New best!" flag, and restart hint, and the win card shows the cleared board. I'm also checking the overlay CSS, centering the cards and letting clicks pass through, and sizing the top-left tag so it stays readable on the small board.

Still writing the styles: I'm setting up the bump animation for the score values, a pulse on the message text, a blinking dot for the tag, and a gradient title on the start card.

Still writing the styles: I'm defining the gradient titles for the start and game-over cards, and I'm working out the hint text colors and the header height.

Still writing the styles: I'm finishing the mobile breakpoint for the header and stat chips, and deciding to keep the footer hints visible even on short screens.

Still writing the styles: I'm adding a touch-action rule so taps and drags on the board don't trigger page zoom, and I'm keeping text selection disabled.

Still writing the HTML: I'm finishing the overlay transitions, so the start card fades in on load when the page initializes, and I'm checking that the start screen is visible at a three-second mark.

Still writing the styles: I'm setting the page background, full-height flex layout, and resetting margins and box sizing.

Still writing the page styles: I'm setting up the header's flex layout with centered content, the body's padding and gradient background, and the app container's column layout.

Still writing the page styles: I'm setting up the header's flex layout with centered content, a brand area with a glowing logo dot, and the stats block that sits on the right.

Still writing the styles: I'm finishing the stat chip layout and the value bump animation.

Still writing the board styles: I'm positioning the canvas absolutely inside the rounded board, with its background and shadow.

Still writing the stylesheet: I'm adding the tag's pill styling and its blinking dot.

Still writing the overlay CSS: I'm placing the overlays absolutely over the board with fade transitions and letting clicks pass through, and starting the card's max width.

Still writing the overlay card styles: rounded corners, padding, a translucent blurred background, and a subtle lift-and-scale transition that settles into place when the overlay shows.

Still writing the styles: I'm setting up the card's text, with a small kicker label, a gradient title with a red variant, and a mint message line that pulses.

Still writing the styles: I'm adding the small badge for a new best score, with its gold tint and tight padding.

Still writing the stylesheet: I'm finishing the keyboard key styling, with small padded keycaps sized to fit their labels.

Still writing the styles: I'm finishing the keycap styling and the hint row, which wraps and keeps each key label on one line.

Still writing the page styles: I'm adding the keyframes for the pulse, blink, and bump effects, and a small-screen breakpoint that tightens the body padding, brand, logo, and stat chips.

Still writing the script: I'm setting up the config constants for the grid size, starting snake length, demo tick speed, input queue limit, and shake duration.

Still writing the script: I'm defining the direction vectors for up, down, left, and right, and the matching lookup arrays, along with the palettes for eating and death particles.

Still writing the script: I'm setting up the DOM references for the board, canvas, score and best displays, the tag, and the overlay cards.

Still writing the script: I'm setting up the mutable state, with the grid scale, the current phase, the snake body and its previous positions, the queued directions, food, and the score values.

Still writing the script: I'm setting up the helper functions for grid indexing, linear interpolation, and the speed curve that gets faster as the snake grows.

Still writing the layout code: I'm working out the board's pixel size from the viewport width, capped at the max board size, and reading the gap between the app's rows to subtract the chrome height.

Still writing the layout code: I'm finishing the board's pixel size, clamping it to the viewport height minus the chrome, then setting the canvas and backing store dimensions.

Checking the layout math: the header height depends on the app width, so I measure it at the width I set first, then shrink the board to the final size, which leaves the header unchanged. If the window is too short, the board floors at 200px and the page will scroll vertically, which is acceptable.

Still writing the background: I'm building the cached board backdrop with a vertical gradient fill and a faint checkerboard of lighter cells.

Still writing the background: I'm adding the grid lines, drawn at rounded pixel positions, and starting a radial vignette that darkens the board's edges.

Still writing the background: I'm applying a radial vignette that darkens the board's edges, then the game logic comes next, with spawning food, steering, and the reset and pause handling.

Still writing the game logic: I'm defining the food spawner, which picks an empty cell at least five steps from the head, and then starting the queue helper that handles direction changes.

Still writing the game logic: I'm finishing the queue helper's guard against reversing direction, then setting up resetGame to rebuild the starting snake, clear the effects, and pick the interval for either a live run or the demo.

Still writing the game logic: I'm setting up the step function, which copies the previous body, applies the queued turn, and checks whether the next head cell is food or a wall.

Still writing the game logic: I'm finishing the step function so the new head is added before food is spawned, and then handling the eat or tail-pop case.

I'm checking the win condition inside eat, and that die keeps the body as it was, since prevBody was copied at the top of the step.

Still writing the eat handler: I'm setting up the food coordinates, bumping the score, and speeding up the tick, then spawning the burst, ring, and popup effects.

Still writing the burst helper: it takes the position, colors, count, and the velocity, life, and size ranges, and scatters each particle at a random angle.

Still writing the game logic: I'm finishing the burst call that spawns the death particles, setting the screen shake timer, and branching on whether this is the demo or a live run.

Still writing the game logic: I'm finishing the death branch, moving the game into a short demo-death pause or a game-over state, and updating the final score and best display.

Still writing the win handler: if the player fills the board it ends the run as a win, and in demo mode it just resets the demo.

Still writing the game logic: I'm wrapping up the win and timer handlers, then starting the UI sync function that toggles the demo tag.

Still writing the UI sync: I'm working out which overlay to show based on the phase, and toggling the demo tag and the pause, over, and won cards.

Still writing the update loop: I'm smoothing the head angle toward the current direction, advancing the fixed-step ticks while the game is playing or in demo, and counting down the phase timer.

Still writing the update loop: I'm working out the head angle's smoothing toward the current direction, then the fixed-step ticks for playing and demo, and the phase timer countdown.

Still writing the particle update: each particle's velocity is damped and nudged downward, then its position advances, and expired particles get removed.

Still writing the render: I'm setting up the transform, drawing the cached backdrop, and computing a screen-shake offset while the shake timer runs.

Still writing the render: I'm drawing the food, the snake, and the effects after applying the screen-shake offset to the backdrop.

Still writing the draw code: I'm setting up the snake render, which takes the body length and checks whether the run has ended, then loops over the segments.

Still writing the snake render: I'm setting up the per-segment position arrays and the line caps, then working backward from the tail toward the neck to draw the tapered body.

Still writing the snake render: I'm stroking each body segment from tail to neck, with the color and width tapering along the way.

Still writing the snake render: I'm working out how the cap at each joint is drawn, since the segment drawn later covers the shared point and its width sets the visible shape.

Still writing the snake render: I'm finishing the joint caps, where the head-side segment's wider cap covers the shared point, and setting up the head with a forward radius sized to the cell.

Still writing the head: I'm drawing the forked tongue as it flicks out from the snout.

Still writing the head: I'm adding the shadow and glow settings, then starting the radial gradient that shades the snake's head.

Still writing the head: I'm finishing the radial gradient fill for the head, switching the palette between the live and dead colors, drawing the ellipse, and then clearing the shadow settings.

Still writing the head: I'm adding the thin darker outline around the ellipse, then setting up the eyes with their positions and radius.

Still writing the eyes: I'm drawing each white eye, then the dark pupil offset toward the front, then a small glint on the pupil, and restoring the canvas state after both eyes are done.

Still writing the snake render: I'm checking the head's facing direction and the pupil offset, then writing the color helper that shades each body segment by its position along the tail.

Still writing the effects: I'm drawing the expanding rings with additive blending, fading each one out as its life runs down.

Still writing the effects: I'm drawing the particles with their fading alpha, then setting up the score text font size.

Still writing the effects: I'm finishing the popup text, setting its font and alignment, and fading each popup out as it rises.

Still writing the keyboard input: I'm mapping the arrow keys and WASD to their directions in a switch.

Still writing the keyboard handler: I'm finishing the arrow and WASD mapping, then handling the space and Enter keys to start a run or pause.

Still writing the keyboard handler: I'm finishing the space and Enter branch, the pause toggle on P, and falling back to start a run on any other key while in demo mode.

Still writing the keyboard handler: I'm checking the pointer input on the board so taps and drags can steer the snake too.

Still writing the pointer handling: I'm finishing the swipe check so a drag picks the dominant axis and steers the snake, and I'm clearing the stored pointer on cancel.

Still writing the input handling: I'm wiring up the pointer release so a short tap triggers the tap action and a longer drag steers the snake, and I'm adding an auto-pause when the page is hidden or loses focus.

Still writing the resize handling: I'm wiring a window resize listener that re-runs the layout, since the render already reads the current size and cell values.

Still wiring up the startup: I'm calling the layout once, resetting into demo mode, and kicking off the frame loop, since the script sits at the end of the body so the elements already exist.

Still writing the frame loop: I'm setting the first delta to zero, clamping long gaps to 100ms, then updating and rendering each frame with the leftover time fraction.

I'm checking how the interval change on eating affects the interpolation fraction, since the accumulator may briefly exceed the new, shorter interval, so the fraction just gets clamped to 1.

Checking the AI's flood-fill logic for the tail check: the mark counter advances inside each flood call, so the reachability test runs right after each direction's flood, and I'm confirming that ordering holds.

Checking the demo AI's first move: the head at (12,12) is blocked along with the body, so the UP candidate's flood has to start from (12,11) and route around the snake's own cells.

Next I'm checking whether the demo AI's first move from the head at (12,12) works: the UP and DOWN candidates both reach the tail and the food through open cells, LEFT is blocked by the body, and RIGHT is open, so I'll pick whichever has the shortest distance to the food.

I'm checking the demo AI's reasoning about the food and the tail: if the food is right next to the head, the flood from that cell gives it a distance of zero and the best score, and the tail check still counts the tail as free space. I'm also considering that the AI will probably stay alive for a while, though it will eventually trap itself as the snake grows, which is fine because the demo just restarts. Then I'm looking at the tick rate of about 115ms, which works out to roughly 8.7 cells per second, and deciding it's a reasonable pace.

Now I'm checking the wall-collision and food-spawn paths, and I'm also weighing whether the demo label might overlap the snake, though it's a minor layout detail. Then I'm confirming that keyboard handling is clean: nothing is focusable, so the default behavior doesn't need suppressing, and quick key presses are each consumed one per step through the input queue.

I'm double-checking the input queue: when it's empty, `dir` still holds the last move that actually ran, so a reverse press is caught against that. Pressing LEFT right after an UP turn is a 90° change and gets queued, which is correct.

Checking the reverse-direction rule against the snake's own tail: with a length-4 snake, the head can step into the cell the tail is vacating, so I need to confirm that case is allowed.

Now I'm checking how the rings and particle effects render, and whether the demo label might sit over the snake at the start.

I'm checking how the start card sits over the snake at the center of the board. It's semi-transparent with a blur, so the snake underneath should still show through, and I'm keeping the card centered rather than moving it to the bottom. The best score reads 0 in demo mode, which is what I want.

Checking the layout math for 1280×800 now: the header is around 52px, the hints about 20px, plus gaps and padding, which should still fit under 800px with room to spare.

Checking the layout at 375px wide: the board shrinks to about 343px and the whole page still fits within 667px tall. In landscape at 667×375, the board drops to roughly 235px, which still fits.

Checking the container sizing at 375px: the app width matches the viewport minus the body padding, so nothing should push past the edge and create a horizontal scrollbar.

Checking the layout math at 343px: the brand and the two stat boxes add up to about 280px, so they fit. The hint row will just wrap onto a few lines.

I'm checking the state transitions now: pressing Space from game over restarts the run and hides the overlays, P toggles pause and resume, and the pause card shows while the frame stays frozen. I also want to confirm that P does nothing during the game-over fade-in.

Now I'm checking the keyboard handling: arrow keys get `preventDefault` so the page doesn't scroll when the game has focus, and touch input runs through pointer events with `touch-action` disabled on the board. I'm also confirming there's no leftover console error risk from the canvas and math calls.

I'm checking the interpolation for the tail when the snake doesn't grow: each body segment should blend from its old position to the one that replaced it.

I'm checking how the interpolation handles the growth step: the body is one segment longer, so the new tail sits on the old tail cell and stays put while the segment ahead of it slides into that spot.

Still tracing how the growth step's tail segment lines up with the one ahead of it, so the gap gets covered.

Now I'm checking the remaining requirements against the spec: the best score tracks the session, game over comes from walls or self-collision with the overlay, Space or Enter restarts, P pauses, and the grid is 24×24 centered via flex.

I'm checking the remaining requirements against the spec: the board is centered, the snake grows by one cell per food eaten, and new food never spawns on the body. Quick key presses are queued and rejected only if they reverse against the previous direction, which is the behavior I want.

Next I'm writing out the full HTML and adding a role and aria-label to the canvas. I'm also checking that the start overlay appears right away and that the AI keeps moving at the 115ms demo tick. The overlays fade in over about 0.28s, so by the three-second screenshot the start card should be fully visible.

I'm checking the transition behavior on first render, which doesn't matter much since the overlays still appear either way. I'm also confirming that clicking the board while paused resumes the game, with the pause card itself ignoring pointer events.

Next I'm checking the click behavior: a tap on the board while paused resumes the game, and a tap after game over restarts only once the delay has run out. I'm also thinking about whether a tap during play should pause, but the spec doesn't ask for that, so I'll leave it out and add "or click" to the game-over prompt.

Now I'm writing the full HTML file, with the canvas, styles, and game loop all in one place.

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing the HTML, now the header, board, and the start, pause, and game-over cards inside it.

Still writing styles...

Still writing constants...

Still writing constants...

Still writing constants...

Still writing constants...

Still writing constants...

Still writing constants...

Still writing the drawing code for the food, sizing its glow and pulse from the current frame time.

Still writing the food drawing, placing the glow and the pulsing radius around the cell center.

Still writing the food drawing, now the gradient fill for the berry body.

Still writing the food drawing, now finishing its highlight.

Still writing the input handlers and the init step.

Now I'm checking how the timer ends the game-over state: when the delay runs out, the game-over card appears and the phase stays as it is.

Checking how the timer hands off once it runs out: the demo's death delay resets the demo, and a win in demo mode waits about 1.5 seconds before doing the same.

Checking the post-death timing now: once the death delay runs out, the game-over card appears, and the demo mode uses its own shorter delay before resetting.

Checking how `die()` handles the head: the snake's previous body is saved before the death check, so the freeze frame lines up. The head keeps easing toward the direction that killed it, so it may turn to face the wall on the way down.

Still writing the flood-fill helper for the AI.

Still writing the flood-fill loop, checking each neighbor cell for bounds before it gets queued.

Still writing the AI's flood-fill neighbor checks.

Still writing the AI's scoring for each candidate direction.

Still writing the AI's scoring for each candidate direction.

Still writing the flood-fill checks for the AI.

Still writing the AI's direction choice: I'm confirming the tie-breaking order, and that a candidate move the snake can't legally make falls back to the current heading.

Still writing the reset and remaining draw code.

Still checking the drawing details: the glow on the bright dots over the dark background, the head turning to follow the smoothed heading, and the tongue flick every 1.7 seconds. I'm also making sure the death X-eyes are drawn with a set line width.

Still writing styles...

Checking the last few requirements: the remaining keyboard hint, and that the start card reads clearly as the opening message. I still need to confirm the demo itself is visible right away, since the spec wants the AI's movement and the particle effects on eating to show within the first few seconds.

Now I'm checking the AI's food-seeking: a spawn at five or more cells from the head means it has a short trip ahead, so the first meal should come within the opening seconds. At the 115ms demo tick, that puts roughly two foods eaten by the three-second mark, and the popups will show "+10" as they go.

Still checking the remaining guards: the toggles on the overlays, tag, and best-score badge, and the final score text. I'm also confirming the canvas setup calls and that nothing in the layout code can produce a NaN.

Checking the remaining engine edge cases now: the snake can't outgrow the board, so the body buffer is big enough, and the typed-array resets look right. I'm also confirming the interval never drops below its minimum and that the demo's empty-food case is guarded before `eat()` runs.

Checking the event handlers now: keyboard input with an undefined key should map to no direction, and the blur and visibility handlers just pause the game.

I'm checking the keyboard edge cases now: if the user taps Up and then Left quickly while moving right, both presses get queued and honored, so the snake goes up one cell and then left.

I'm running the input scenarios on the snake's queue: a quick Down then Right while heading Right gets both honored, and Left then Down while heading Up also queues cleanly. I'm also confirming that a press directly opposite the current heading with an empty queue is ignored, so the snake can't reverse onto itself.

I'm checking the reversal cases for queued input: if an Up is already queued and a Down comes in, the Down is dropped since it would reverse the snake. I'm also confirming that a queue of Up then Left while moving right works, because each turn is checked against the last queued direction, not the current heading.

Checking the queued-input case: an Up already queued and a Down arriving next gets dropped, but Up then Right is fine, since each press is compared against the last queued direction. Once a queued move runs, the next one is measured against that same heading, so the snake can't double back. A restart from the game-over screen resets the heading to Right.

I'm checking the keyboard restart path: holding an arrow key while on the game-over screen just fires repeated events that get ignored. I'm also confirming that P does nothing in that state and that the paused queue is left alone, then looking at whether the small-screen hint row keeps its groups within the width.

Still wrapping up the final file: I'm checking the header layout and the board's background colors, then writing the whole thing out in one pass.

Still writing the layout function: I'm sizing the board to fit the viewport and checking that the gap and padding read back as numbers.

Still writing the layout sizing: I'm computing the board size from the viewport and the header and hint heights, then applying that size to the app, board, and canvases.

Still sizing the board: I'm capping the width to the viewport, subtracting the header, hint, and gap heights from the available height, and applying the resulting square size to the canvases.

Now I'm finishing the layout sizing: the board's width and height come from the viewport, and the same square size goes to the app, board, and both canvases.

Now I'm writing the stylesheet for the page: the dark background, the text colors, and the faint grid lines.

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Still writing styles...

Now I'm writing the stylesheet's last rules: the mobile breakpoint, the keyboard badges, and the overlay text.

Still writing constants: the board is 24 by 24 with a starting length of four, and the demo ticks every 115ms with a small turn buffer.

Still writing the script's constants and DOM lookups.

Still writing the script's constants and DOM lookups.

Still writing the script's state variables: the heading, the buffered turns, the score and best counters, and the particle, ring, and popup lists.

Still writing the script's helpers: the grid index, the lerp and speed functions, and the direction checks.

Still writing the layout sizing: I'm measuring the viewport and the header and hint heights to work out how big the board can be.

Still writing the layout sizing: I'm finishing the board size calculation and applying it to the app, board, and both canvases, then building the background.

Still writing styles...

Still writing game logic: I'm defining the queued-turn helper and the reset routine that sets up the starting snake and clears the state.

Still writing the game loop: I'm setting up the step function to pick the next direction, either from the AI in demo mode or from the queued player input, and tracking the previous body for smooth motion.

Still writing the collision check: I'm computing the next head cell, letting the tail count as free on a normal move, and calling the death routine if the snake hits a wall or itself.

Still writing the game loop: I'm adding the eat handler, which bumps the score, speeds up the snake, and spawns a burst of particles and a popup at the food's cell.

Still writing the die routine: I'm bursting death particles at the head, setting the shake timer, and branching between the demo restart and the game-over screen with the final score.

Still writing the game flow: I'm defining the death and win handlers, which pick the demo or game-over path and reset the phase timers.

Still writing the game controls: I'm defining the timer callback and the UI sync, which shows the right overlay for the current phase.

Still writing the game loop: I'm smoothing the head's angle toward its heading and advancing the snake on each tick while the game is playing or in demo mode.

Still writing styles...

Still writing the frame loop: I'm computing the time step from the last frame and passing it into the update.

Still writing the frame loop: I'm defining the keyboard-to-direction mapping for the arrow keys and WASD.

Still wiring up the keyboard handler: arrow and WASD keys queue turns or start the game from the demo, and Space, Enter, and P are handled separately.

Still writing the input handling: the keydown handler now covers Space, Enter, and P, and pauses only while playing or paused.

Still writing the input handling: the pointer handlers now decide between a tap and a swipe, turning a short movement into a turn once the game is running.

Still wiring up the page's startup: I'm handling the visibility and blur events to auto-pause, and the resize event to re-run the layout.

Still writing the render function: I'm setting up the canvas transform with the device pixel ratio before drawing the frame.

Still writing the render pass: I'm applying a small screen shake offset after the background, then drawing the food, snake, and effects.

Still writing the draw-snake routine: I'm setting up the context and reading the body length and the dead state.

Still writing styles...

Still writing the draw-snake routine: I'm drawing the head with a rotation and a tongue that flicks out on a timer.

Still writing the head's tongue: I'm drawing it with a flick and then setting up the glow shadow for the head.

Still writing the head's glow and gradient fill.

Still writing the head's outline: I'm drawing the ellipse, clearing the shadow, and stroking a thin edge in a color that matches the dead or alive state.

Still writing the head's outline: I'm re-creating the ellipse path so the stroke goes around it cleanly, then setting up the eyes.

Still writing the eye drawing: I'm setting up the eye positions and, for a dead snake, drawing crossed-out X eyes.

Still writing the eye highlights: the white eyeballs, the dark pupils offset toward the heading, and the small catchlights.

Still writing the segment color helper, setting up the alternating band so every other body segment gets a slightly darker tone.

Still writing segment colors: I'm picking the red palette for a dead snake or the green one for a live one, then darkening every other segment for a banded look.

Still writing the head outline: I'm fine-tuning the body joints and tail thickness so the snake reads as a segmented shape.

Still writing the head's outline: I'm checking that the head's size and the eyes' placement give it a distinct shape from the neck, and that the heading angle eases toward the current direction.

Still writing the draw-effects routine: I'm drawing the expanding rings with fading alpha and starting the loop over the particles.

Still writing the popup text: I'm setting up the font, alignment, and fill color for the score labels.

Still writing the popup text: I'm looping over the active popups, fading them and floating each one upward before drawing it.

Still writing the head's outline: I'm checking that the stroke and fill don't leave the head's line style set to round for later drawing.

Still writing the effects update: I'm applying drag to each particle and stepping its position, then expiring finished particles and rings.

Still writing the effects update: I'm applying drag and gravity to each particle, then expiring finished particles, rings, and popups.

Still checking the layout helper: I'm confirming it runs before the game resets, and looking at how it reads the row gap from the app element.

Still checking the layout: I'm confirming the gap and footer values add up into the total chrome height, including the margin.

Still checking the code for missing or duplicate declarations, going through the helper functions for input, updates, and rendering.

Still checking the code for function hoisting and declaration order, making sure the helpers and constants are defined before the startup calls run.

Checking the remaining references in the script, specifically that the AI helper and the flood fill use the grid constants correctly.

Still checking the code's variable declarations and the render signature, making sure the frame timing passes the right interval fraction into the render call.

Still double-checking the startup path: I'm confirming `headAngle` begins at zero for the rightward heading, and that the saved body copy is taken right after the reset.

Still double-checking the reset path: I'm confirming the body, queue, heading, timers, and food are all set before the UI syncs, and that the interval gets reset from the speed helper.

Still checking the AI's first decision: it reads the food position right after the reset, and the blocked grid gets rebuilt from the body on every call, so the tail cell stays open.

Still checking for unbounded loops in the helpers: the BFS queue loop ends once the queue is drained, and the start cell is confirmed to be inside the grid.

Next I'm checking the overlay wording: the start card gets a kicker and a "Click or press a key" prompt, the pause overlay just says to resume, and the game-over card is coming up next.

Still writing the game-over overlay: I'm settling on a short restart prompt and deciding whether to keep the extra "tap the board" line.

Still writing the CSS: I'm adding a red glow to the board for the game-over state and a short transition on its shadow.

Checking the "New best!" badge: it only shows when the score beats the best from when this run started. Next I'm making sure the game-over overlay displays the final score, and that the Space and Enter restart keys and the P pause key behave as intended. Pressing P during the death delay does nothing, and arrow keys are ignored on the game-over screen, though I still block their default browser action.

Next I'm checking the demo's death behavior: the snake flashes red with X eyes and the board shakes before a fresh demo starts, and the game-over overlay never appears in demo mode. I'm also confirming the phase timer handling and the tap action when the timer hits zero.

Checking the timer handling next: the demo restarts after the win delay, and the phase only advances when the update step runs in playing or demo mode. I'm also confirming that the dead demo snake keeps its heading while it waits.

Checking the CSS layering next: the overlay and tag sit above the canvas, which is absolutely positioned inside the board with no z-index of its own. I'm also confirming that the board's overflow hidden won't clip its outer box-shadow, and that the app container's width gets set by the script.

I'm checking that `body` is a flex container with `.app` as its only child, and that the layout centers vertically at 1280×800. I'm also confirming the overlay and tag stay absolutely positioned so nothing causes a horizontal scrollbar, and that the hint keys and the title's letter-spacing look right.

Checking the remaining CSS details now: the pulsing message should stay visible at its lowest opacity, the mint color gives it enough contrast, and the tag in the top-left shouldn't get in the way of the snake's path. I'm also confirming the `:root` variables are defined where they're used, and that the unused rose variable can go.

Next I'm weighing the input timing: each tick consumes one queued turn, so a key press can wait up to 128ms, which is normal for snake. Two quick presses within one tick both sit in the queue and get applied on successive ticks, so neither is lost.

Checking how a queued turn behaves when the snake is heading right and the player presses up and then left: it turns up, then left. I'm also making sure the queue carries over through a pause, and that the direction check against the queue holds up while a step is still pending. Next I'm looking at self-collision: the limit is body length minus one when not eating, so the tail cell is allowed to move away. When the snake eats, the limit grows to the full length, so entering the tail cell counts as a crash. Food never spawns on the snake, so that case can't come up at the tail.

Now I'm checking the self-collision case when the head enters the tail cell while eating, which can't happen since food never spawns on the snake. I'm also confirming that reversing into the neck is blocked by input and still counts as a crash, and that a zero-length move isn't possible. The small particle burst and the "+10" popup look fine, and I'm checking the ring's stroke width as it shrinks.

I'm checking the glow on the snake's head: the shadow blur is set from the cell size, but canvas shadow blur doesn't scale with the device-pixel transform, so on high-DPI screens it will look smaller than intended and may need to be multiplied by the DPR.

Checking the blur value again: canvas shadow blur doesn't follow the transform, so on high-DPI screens it needs multiplying by the device pixel ratio to look right. I'll make that change and then consider adding an occasional eye blink for a bit of polish.

Adding a blink to the eyes: every few seconds they'll flatten into thin lines for a moment, and the shadow blur on the head gets scaled by the device pixel ratio.

Checking the overlay text at 375px next: the start card's message is about 260px wide, which will wrap onto two lines inside the roughly 250px of usable width.

Now I'm checking the small details: the heading "Snake" in the title, the card's reduced padding on mobile so the text wraps cleanly, and whether the header brand should match the gradient on the start card. I'm also thinking about whether a favicon is needed.

I'm adding a favicon link so the browser doesn't request /favicon.ico and log a 404 in the console. An inline data URI avoids any network request entirely.

Still writing the favicon link...

Checking the start message's wording and whether the page-load background iframe affects the demo; the demo should still run since the animation loop keeps going.

Writing the final HTML document now...

Still writing the HTML document...

Still checking the head's shading: its outline is a thin dark green stroke, and the gradient reaches past the ellipse edge, which is fine. I'm also confirming the body's odd segments get the darker band and that the dead snake's body switches to red, and that the round caps keep the corners smooth where the snake turns.

Still writing the Snake code...

Checking whether the AI's path could run through the tail cell: it should be vacated by the time the head arrives, since the tail moves away every tick. Anything else on the path is blocked, so that's the only case to rule out, and the `reachesTail` check covers it. The lookahead also seems safe, since cells ahead of the head are free. The AI may loop for a long time but should eventually die as the snake grows, and then it restarts.

Next I'm checking the AI's fallback: if no move is valid it returns the current direction, which may be blocked, and the step just ends the round and restarts the demo. I'm also making sure reversing is skipped by the opposite-direction check, and that the food-missing case is handled without error.

Still writing the final file, making sure every brace and semicolon matches.

Still writing the CSS variables and body styling, including the gradient background behind the page.

Still writing the CSS, now the header and the logo's glow.

Still writing the CSS, now the board's styling and the stat cards.

Still writing the board's CSS, including the danger-state shadow.