GPT-5 Nano
by OpenAIReasoning1 console error
Running live in a sandboxed frame. Click inside it before using the keyboard.
How it went
- Total time
- 1 min 29 s
- Cost
- $0.0047
- Output tokens
- 11,731
- Spent thinking
- 6,848 tokens
- Speed
- 139.4 tok/s
- Console errors
- 1
- First token after
- 4.4 s
- First visible text after
- 58.3 s
- Prompt tokens
- 493
- Code size
- 17.9 KB
- Finish reason
- stop
- Served by
- OpenAI
- Model id
openai/gpt-5-nano- Reasoning sent
model default- Max output
- 128,000 tokens
- Generated
- Nov 12, 2026
Console errors
Caught in the first 3 seconds after load, in a sandboxed iframe like the one above.
Identifier 'startOverlay' has already been declared
What it was asked
The prompt
Build an interactive Kanban board in vanilla HTML, CSS and JavaScript (no framework, no library). Requirements: - Three columns: "To do", "In progress", "Done", each showing its card count. - Pre-populate the board with 6 realistic cards spread across the columns so the first screenshot looks alive. - Each card has a title and a priority (low / medium / high) shown as a colored badge. - Add a card through a small modal form (title required), and delete a card with a button on it. - Drag and drop cards between columns with the mouse, with a clear visual drop indicator. - A search field that filters cards live by title. - A light / dark theme toggle. - State lives in memory only (no storage APIs).
System prompt, sent with every prompt
You are generating a self-contained web demo. It will be rendered automatically in a sandboxed iframe and compared side by side with the output of other AI models given the exact same task. Output rules: - Reply with exactly ONE fenced code block containing the complete file: ```html (or ```svg when the task asks for an SVG). No text before or after the code block. - Everything must be inline: CSS in <style>, JavaScript in <script>. No external files, images, fonts or network requests, except the CDN URLs explicitly allowed by the task. - Do not use localStorage, sessionStorage, cookies, IndexedDB, alert(), confirm(), prompt() or window.open(): they are blocked in the sandbox and will throw. - The page must look right in a 1280×800 viewport and adapt gracefully down to 375px wide. No horizontal scrollbar. - Something meaningful must be visible on first paint: a screenshot is taken automatically about 3 seconds after load, without any interaction. - Everything that makes the demo interesting must be visible within the first seconds: nothing hidden behind a high score, a later level or a long play session. - Games must start in a self-playing demo mode (a simple AI plays) behind a "Click or press a key to start" message, so the game can be judged in action without playing. - The iframe only receives keyboard events after the user clicks it: if the demo uses the keyboard, display a clear "Click or press a key to start" message. - The code must run with zero errors in the console of the latest Chrome.
Code run-1.html · 507 lines
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>Vanilla Kanban Board</title>
<style>
:root {
--bg: #f6f7fb;
--card: #ffffff;
--surface: #ffffff;
--text: #0f172a;
--muted: #6b7280;
--border: #e5e7eb;
--shadow: 0 2px 8px rgba(0,0,0,.06);
--accent: #4f46e5;
--overlay: rgba(2,6,23,.8);
--chip-low: #e5e7eb;
--chip-medium: #f59e0b;
--chip-high: #ef4444;
}
[data-theme="dark"] {
--bg: #0b1020;
--card: #141a2a;
--surface: #111428;
--text: #e5e7eb;
--muted: #a3a3a3;
--border: #2a2f58;
--shadow: 0 6px 18px rgba(0,0,0,.5);
--overlay: rgba(0,0,0,.6);
--chip-low: #374151;
--chip-medium: #f59e0b;
--chip-high: #f87171;
}
* { box-sizing: border-box; }
html, body { height: 100%; }
body {
margin: 0;
font-family: system-ui, -apple-system, "Segoe UI", Roboto, Inter, Arial;
background: linear-gradient(#f8f9ff, #eef2ff);
color: var(--text);
overflow-x: hidden;
}
#app.theme-dark {
background: #0b1020;
}
/* Overlay start message */
.overlay {
position: fixed; inset: 0;
background: var(--overlay);
display: flex; align-items: center; justify-content: center;
z-index: 50;
color: #fff;
text-align: center;
padding: 20px;
user-select: none;
}
.overlay.hidden { display: none; }
.overlay .start-card {
background: rgba(0,0,0,.25);
border-radius: 12px;
padding: 28px 28px;
max-width: 520px;
box-shadow: 0 8px 24px rgba(0,0,0,.25);
border: 1px solid rgba(255,255,255,.25);
}
.overlay h2 { margin: 0 0 8px 0; font-size: 1.4rem; }
.overlay p { margin: 6px 0; opacity: .95; }
/* Layout header */
.header {
display: flex; align-items: center; justify-content: space-between;
padding: 14px 20px;
position: sticky; top: 0;
background: color-m-mix(in oklab, white 95%, black 0%);
z-index: 5;
border-bottom: 1px solid var(--border);
}
.brand {
font-weight: 700; font-size: 1.05rem;
letter-spacing: .2px;
}
.controls { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.btn {
border: 1px solid var(--border);
background: #fff;
color: var(--text);
padding: 8px 12px;
border-radius: 8px;
cursor: pointer;
font-weight: 500;
box-shadow: 0 1px 2px rgba(0,0,0,.04);
}
.btn:hover { transform: translateY(-1px); }
.btn-primary {
background: var(--accent);
color: white;
border: none;
}
.search {
padding: 8px 12px;
border-radius: 8px;
border: 1px solid var(--border);
min-width: 220px;
outline: none;
background: #fff;
}
/* Board */
.board {
display: grid;
grid-template-columns: repeat(3, 1fr);
gap: 16px;
padding: 16px 20px 40px;
max-width: 1200px;
margin: 0 auto;
width: 100%;
}
.column {
background: var(--surface);
border: 1px solid var(--border);
border-radius: 12px;
display: flex; flex-direction: column;
min-height: 420px;
box-shadow: var(--shadow);
overflow: hidden;
}
.column-header {
padding: 12px 12px;
display: flex; justify-content: space-between; align-items: center;
border-bottom: 1px solid var(--border);
background: color-mix(in oklab, white 60%, black 0%);
}
.column-header h3 { margin: 0; font-size: 0.95rem; font-weight: 700; }
.count {
background: #e5e7eb;
color: #374151;
font-size: 12px;
padding: 2px 8px;
border-radius: 999px;
min-width: 22px; text-align: center;
}
.column[data-column="todo"] .column-header { background: color-mix(in oklab, white 70%, black 0%); }
.column-content {
padding: 8px;
display: flex; flex-direction: column; gap: 8px;
min-height: 360px;
transition: background .2s ease;
}
.column.drag-over { outline: 3px dashed #4f46e5; outline-offset: -6px; background: color-mix(in oklab, #e0e7ff 40%, white 0%); }
.card {
background: var(--card);
border: 1px solid var(--border);
border-radius: 10px;
padding: 10px 12px;
display: flex; align-items: center; justify-content: space-between;
box-shadow: 0 1px 2px rgba(0,0,0,.04);
cursor: grab;
}
.card.dragging { opacity: .6; transform: scale(1.02); }
.card-content { display: flex; align-items: center; gap: 8px; min-width: 0; }
.card-title { font-weight: 600; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; max-width: 180px; }
.badge {
padding: 4px 8px; border-radius: 999px; font-size: 11px; font-weight: 700; text-transform: capitalize;
border: 1px solid rgba(0,0,0,.05);
}
.priority-low { background: var(--chip-low); color: #374151; }
.priority-medium { background: var(--chip-medium); color: #fff; }
.priority-high { background: var(--chip-high); color: #fff; }
.delete {
background: transparent; border: none; color: #b91c1c;
font-size: 14px; padding: 4px; border-radius: 6px; cursor: pointer;
}
.delete:hover { background: rgba(185,28,28,.1); }
/* Responsive */
@media (max-width: 1020px) {
.board { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 700px) {
.board { grid-template-columns: 1fr; }
}
/* Start overlay click any area to hide (no keyboard requirement) */
.overlay .start-card p { margin: 6px 0; opacity: .95; }
</style>
</head>
<body>
<div id="app" class="theme-light">
<div id="startOverlay" class="overlay" aria-label="Start overlay">
<div class="start-card" role="presentation">
<h2>Kanban Board</h2>
<p>Drag and drop cards between columns. Use the Add Card button to create new tasks. Type in Search to filter by title.</p>
<p><strong>Click anywhere or press any key to start</strong></p>
</div>
</div>
<header class="header" aria-label="Top bar">
<div class="brand">Kanban Board</div>
<div class="controls">
<input id="search" class="search" type="search" placeholder="Search tasks…" aria-label="Search tasks" />
<button id="themeToggle" class="btn" title="Toggle theme">Theme</button>
<button id="addCardBtn" class="btn btn-primary" title="Add a new card">Add Card</button>
</div>
</header>
<main class="board" id="board" aria-label="Kanban board">
<section class="column" data-column="todo" aria-label="To do column">
<div class="column-header">
<h3>To do</h3>
<span class="count" data-for="todo">0</span>
</div>
<div class="column-content" role="list" aria-label="To do tasks"></div>
</section>
<section class="column" data-column="inprogress" aria-label="In progress column">
<div class="column-header">
<h3>In progress</h3>
<span class="count" data-for="inprogress">0</span>
</div>
<div class="column-content" role="list" aria-label="In progress tasks"></div>
</section>
<section class="column" data-column="done" aria-label="Done column">
<div class="column-header">
<h3>Done</h3>
<span class="count" data-for="done">0</span>
</div>
<div class="column-content" role="list" aria-label="Done tasks"></div>
</section>
</main>
<!-- Add Card Modal -->
<div id="modalBackdrop" class="hidden" aria-hidden="true" style="position: fixed; inset:0; background: rgba(0,0,0,.5); display:flex; align-items:center; justify-content:center; z-index: 40;">
<div class="modal" role="dialog" aria-label="Add card" style="background:#fff; padding:16px 16px; border-radius:12px; width: min(420px, 90%); box-shadow: 0 6px 20px rgba(0,0,0,.25);">
<h3 style="margin:6px 0 12px 0;">Add Card</h3>
<div style="display:flex; flex-direction:column; gap:8px;">
<label for="cardTitle" style="font-weight:600;">Title</label>
<input id="cardTitle" type="text" placeholder="e.g., Fix login bug" style="padding:8px 10px; border:1px solid var(--border); border-radius:6px;" />
<label for="cardPriority" style="font-weight:600;">Priority</label>
<select id="cardPriority" style="padding:8px 10px; border-radius:6px; border:1px solid var(--border);">
<option value="low">Low</option>
<option value="medium" selected>Medium</option>
<option value="high">High</option>
</select>
</div>
<div style="display:flex; justify-content:flex-end; gap:8px; margin-top:12px;">
<button id="cancelAdd" class="btn">Cancel</button>
<button id="confirmAdd" class="btn btn-primary" disabled>Add Card</button>
</div>
</div>
</div>
</div>
<script>
(function () {
// In-memory store
const initialCards = [
{ id: 'c1', title: 'Set up project repository', priority: 'high', column: 'todo' },
{ id: 'c2', title: 'Plan sprint backlog', priority: 'Medium'.toLowerCase(), column: 'todo' },
{ id: 'c3', title: 'Design landing page', priority: 'high', column: 'inprogress' },
{ id: 'c4', title: 'Implement drag-and-drop', priority: 'medium', column: 'inprogress' },
{ id: 'c5', title: 'Write unit tests', priority: 'low', column: 'done' },
{ id: 'c6', title: 'Deploy to staging', priority: 'low', column: 'done' }
].map((c, idx) => ({ ...c, id: c.id || `c${idx+1}` }));
let cards = initialCards.slice();
let searchQuery = '';
const startOverlay = document.getElementById('startOverlay');
const searchInput = document.getElementById('search');
const addCardBtn = document.getElementById('addCardBtn');
const themeToggle = document.getElementById('themeToggle');
const modalBackdrop = document.getElementById('modalBackdrop');
const cardTitleInput = document.getElementById('cardTitle');
const cardPrioritySelect = document.getElementById('cardPriority');
const cancelAdd = document.getElementById('cancelAdd');
const confirmAdd = document.getElementById('confirmAdd');
// Board columns
const columnContentEls = {
todo: document.querySelector('.column[data-column="todo"] .column-content'),
inprogress: document.querySelector('.column[data-column="inprogress"] .column-content'),
done: document.querySelector('.column[data-column="done"] .column-content')
};
// Helper to render a single card element
function renderCardEl(card) {
const cardEl = document.createElement('div');
cardEl.className = 'card';
cardEl.draggable = true;
cardEl.dataset.id = card.id;
// Build inner structure without innerHTML for safety
const contentDiv = document.createElement('div');
contentDiv.className = 'card-content';
const titleSpan = document.createElement('span');
titleSpan.className = 'card-title';
titleSpan.textContent = card.title;
const badge = document.createElement('span');
badge.className = 'badge';
const pr = (card.priority || 'low').toLowerCase();
badge.textContent = pr;
if (pr === 'low') badge.className += ' priority-low';
else if (pr === 'medium') badge.className += ' priority-medium';
else if (pr === 'high') badge.className += ' priority-high';
// Ensure badge has correct class (avoid duplication)
// badge.className = 'badge ' + (pr === 'low' ? 'priority-low' : pr === 'medium' ? 'priority-medium' : 'priority-high');
// We set to contentDiv
contentDiv.appendChild(titleSpan);
contentDiv.appendChild(badge);
const delBtn = document.createElement('button');
delBtn.className = 'delete';
delBtn.setAttribute('aria-label', 'Delete card');
delBtn.textContent = '✕';
// Assemble
cardEl.appendChild(contentDiv);
cardEl.appendChild(delBtn);
// Events
cardEl.addEventListener('dragstart', (e) => {
e.dataTransfer.effectAllowed = 'move';
e.dataTransfer.setData('text/plain', card.id);
requestAnimationFrame(() => cardEl.classList.add('dragging'));
});
cardEl.addEventListener('dragend', () => cardEl.classList.remove('dragging'));
delBtn.addEventListener('click', (e) => {
e.stopPropagation();
deleteCard(card.id);
});
return cardEl;
}
// Render board according to current state and search
function renderBoard() {
// Clear columns
for (const key of ['todo','inprogress','done']) {
columnContentEls[key].innerHTML = '';
}
// Filter by search
const q = searchQuery.trim().toLowerCase();
const visible = cards.filter(c => {
const matchesColumn = c;
const titleMatches = q.length === 0 || (c.title && c.title.toLowerCase().includes(q));
return titleMatches;
});
// For counts per column, only consider visible cards in that column
const byColumn = { todo: [], inprogress: [], done: [] };
visible.forEach(c => byColumn[c.column].push(c));
// Create DOM
Object.keys(byColumn).forEach(col => {
byColumn[col].forEach(card => {
const el = renderCardEl(card);
columnContentEls[col].appendChild(el);
});
});
// Update counts
['todo','inprogress','done'].forEach(col => {
const countEl = document.querySelector(`.column[data-column="${col}"] .count`);
if (countEl) countEl.textContent = byColumn[col].length;
});
}
// Card operations
function deleteCard(id) {
cards = cards.filter(c => c.id !== id);
renderBoard();
}
function addCard({ title, priority }) {
const newCard = {
id: 'c' + Math.random().toString(36).slice(2, 7),
title,
priority: (priority || 'low').toLowerCase(),
column: 'todo'
};
cards.push(newCard);
renderBoard();
}
// Drag & drop: allow dropping into columns
function setupDragAndDrop() {
const containers = document.querySelectorAll('.column-content');
containers.forEach(container => {
container.addEventListener('dragover', (e) => {
e.preventDefault();
const col = container.closest('.column').dataset.column;
// highlight column as drop target
container.closest('.column').classList.add('drag-over');
e.dataTransfer.dropEffect = 'move';
});
container.addEventListener('dragleave', () => {
container.closest('.column').classList.remove('drag-over');
});
container.addEventListener('drop', (e) => {
e.preventDefault();
const id = e.dataTransfer.getData('text/plain');
const targetCol = container.closest('.column').dataset.column;
const card = cards.find(c => c.id === id);
if (card && card.column !== targetCol) {
card.column = targetCol;
}
container.closest('.column').classList.remove('drag-over');
renderBoard();
});
});
}
// Start overlay: hide on click or any key
function hideStartOverlay() {
startOverlay.classList.add('hidden');
// Allow keyboard after start (no special handling needed)
}
// Init
const startOverlay = document.getElementById('startOverlay');
// Click or key to start
document.addEventListener('keydown', () => {
if (!startOverlay.classList.contains('hidden')) hideStartOverlay();
});
document.addEventListener('click', () => {
if (!startOverlay.classList.contains('hidden')) hideStartOverlay();
});
// Modal logic
const addCardBtnEl = document.getElementById('addCardBtn');
addCardBtnEl.addEventListener('click', () => {
modalBackdrop.style.display = 'flex';
modalBackdrop.setAttribute('aria-hidden', 'false');
cardTitleInput.value = '';
cardPrioritySelect.value = 'low';
confirmAdd.disabled = true;
requestAnimationFrame(() => cardTitleInput.focus());
});
cancelAdd.addEventListener('click', () => {
modalBackdrop.style.display = 'none';
modalBackdrop.setAttribute('aria-hidden', 'true');
});
cardTitleInput.addEventListener('input', () => {
confirmAdd.disabled = cardTitleInput.value.trim().length === 0;
});
confirmAdd.addEventListener('click', () => {
const title = cardTitleInput.value.trim();
const priority = cardPrioritySelect.value;
if (title.length > 0) {
addCard({ title, priority });
modalBackdrop.style.display = 'none';
modalBackdrop.setAttribute('aria-hidden', 'true');
}
});
// Theme toggle
function setTheme(mode) {
const root = document.documentElement;
const app = document.getElementById('app');
if (mode === 'dark') {
root.setAttribute('data-theme', 'dark');
app.classList.remove('theme-light');
app.classList.add('theme-dark');
} else {
root.setAttribute('data-theme', 'light');
app.classList.remove('theme-dark');
app.classList.add('theme-light');
}
}
themeToggle.addEventListener('click', () => {
const current = document.documentElement.getAttribute('data-theme') || 'light';
setTheme(current === 'light' ? 'dark' : 'light');
});
// Search live filter
searchInput.addEventListener('input', (e) => {
searchQuery = e.target.value || '';
renderBoard();
});
// Initialize
setTheme('light');
renderBoard();
setupDragAndDrop();
})();
</script>
</body>
</html>Reasoning trace (6,848 tokens)
**Analyzing project requirements** I need to create a self-contained HTML file that includes vanilla JS/CSS/HTML, with no external files. I'll set up three columns displaying six cards, each with a title and a priority badge. There should be a modal form to add cards and functionality to delete them. Of course, drag and drop, live search, and theme toggle features will be essential. I’m uncertain about the "auto-play" mode since it's geared toward games, not my Kanban board.**Considering demo mode for the board** I’m contemplating whether the kanban board really needs a demo mode since the user didn’t mention it. The guidelines suggest an interactive game should have a "Click or press a key to start" message, but that may not be necessary for my app. While the board utilizes search and drag-and-drop features, which don’t depend on keyboard events, I could add an overlay that reveals the board upon clicking. Still, it’s not essential since drag and drop works with the mouse.**Evaluating keyboard events and overlays** I’m realizing that the search field involves typing, but the iframe captures keyboard events only after it’s clicked. To be safe, I could add a small overlay saying "Click anywhere to start" to clarify there’s no need for keyboard input. Since the app doesn't rely on keyboard interactions, this overlay can vanish with the first click. The guideline about starting a game in a demo mode doesn't apply here, so I can ignore that. I'll also create a modal for adding cards with required fields for title and priority.**Planning features for the kanban board** I’m thinking of adding an "Add Card" button that opens a modal. Each card will have a small 'Delete' button for easy removal. For drag and drop functionality, I'll use the HTML5 drag-and-drop API, making each card draggable within columns that will act as drop zones with a visual drop indicator like a dashed border. For the live search filter, I’ll create an input that filters cards by title in a case-insensitive manner. I'll also implement a theme toggle switch for light and dark modes without the need for persistent storage.**Drafting Kanban board implementation** I plan to start with an initial data array for six cards across columns like "To do," "In progress," and "Done." Each column will display a card count that updates dynamically based on visible cards. For adding and deleting cards, I’ll implement a modal with fields for title and priority. The drag-and-drop feature will allow cards to move between columns, with visual drop indicators for clarity. I'll ensure the layout is responsive, using CSS grid to manage column stacking on smaller screens, while also ensuring no external images are used, opting for system fonts instead.**Setting up initial card data and styles** I’m pre-populating the kanban board with an array of initial cards that includes unique IDs and priorities. For priority colors, I’m considering green for low, orange for medium, and red for high, with style as small rounded pills. To enable drag-and-drop, I’ll set the draggable attribute on card elements and add necessary event listeners. The delete button will use event delegation for efficient handling, triggering a function to remove the card. Additionally, I need to implement real-time search filtering and set up a "Click to start" overlay that disappears upon the user’s first interaction.**Structuring the code and styles** I'm setting up the code structure for the kanban board with constants for columns and a variable array for cards. I'll create the necessary HTML elements and use event listeners for interactions like adding and deleting cards, as well as drag-and-drop functionality. The rendering function will filter visible cards based on a search query and update counts accordingly. Additionally, I'll ensure styles account for themes, and drop indicators and implement a helper function to escape HTML to prevent XSS attacks. Let's make sure everything is responsive and visually appealing!**Crafting CSS and functionality** I'm setting up the CSS for the kanban board to create a visually appealing layout based on the selected theme. This includes styling for the body, headers, controls, columns, and cards, with distinct colors for priority badges. I also need to implement an overlay for user interaction at the start and ensure event listeners properly handle drag-and-drop functionality for card movement. I'll carefully define an `escapeHtml` function to prevent XSS during content handling, keeping user input safe. It's important to ensure everything works seamlessly!**Implementing card creation and setup** I'm implementing card creation by dynamically creating elements instead of using innerHTML. This will involve making a title element and a badge for priority. I've decided that the "Add Card" modal will default to placing new cards in the "To do" column. I'm also ensuring that the overlay instructs users to click to start. I'll craft the full HTML step by step, carefully managing the layout, styles, and functionality for a smooth user experience.