Models 44

Gemini 3.8 Flash

by GoogleReasoningClean
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Running live in a sandboxed frame. Click inside it before using the keyboard.

How it went

Total time
3 min 33 s
Cost
$0.120
Output tokens
31,925
Spent thinking
18,044 tokens
Speed
151.1 tok/s
Console errors
0
First token after
2.2 s
First visible text after
2 min 14 s
Prompt tokens
507
Code size
41.3 KB
Finish reason
stop
Served by
Google
Model id
google/gemini-3.8-flash
Reasoning sent
{"effort":"high"}
Max output
65,536 tokens
Generated
Nov 12, 2026

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 · 1428 lines

<!DOCTYPE html>
<html lang="en" data-theme="dark">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Kanban Flow</title>
  <style>
    :root {
      --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
      --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
      
      /* Dark Theme (Default) */
      --bg-canvas: #090d16;
      --bg-header: #0f172a;
      --bg-column: #111827;
      --bg-column-header: #162032;
      --bg-card: #1e293b;
      --bg-card-hover: #243248;
      --border-subtle: #243248;
      --border-strong: #334155;
      --text-main: #f8fafc;
      --text-muted: #94a3b8;
      --text-faint: #64748b;
      --accent: #3b82f6;
      --accent-hover: #2563eb;
      --accent-glow: rgba(59, 130, 246, 0.25);
      
      --card-shadow: 0 2px 5px rgba(0, 0, 0, 0.4), 0 1px 2px rgba(0, 0, 0, 0.3);
      --card-shadow-hover: 0 10px 22px rgba(0, 0, 0, 0.5), 0 3px 8px rgba(0, 0, 0, 0.3);
      --drop-placeholder-bg: rgba(59, 130, 246, 0.12);
      --drop-placeholder-border: #3b82f6;

      /* Priorities */
      --p-high-bg: rgba(239, 68, 68, 0.18);
      --p-high-text: #fca5a5;
      --p-high-dot: #ef4444;

      --p-med-bg: rgba(245, 158, 11, 0.18);
      --p-med-text: #fcd34d;
      --p-med-dot: #f59e0b;

      --p-low-bg: rgba(14, 165, 233, 0.18);
      --p-low-text: #7dd3fc;
      --p-low-dot: #0ea5e9;

      /* Column Accents */
      --col-todo: #38bdf8;
      --col-progress: #f59e0b;
      --col-done: #10b981;
    }

    [data-theme="light"] {
      --bg-canvas: #f1f5f9;
      --bg-header: #ffffff;
      --bg-column: #e2e8f0;
      --bg-column-header: #e8edf4;
      --bg-card: #ffffff;
      --bg-card-hover: #f8fafc;
      --border-subtle: #cbd5e1;
      --border-strong: #94a3b8;
      --text-main: #0f172a;
      --text-muted: #64748b;
      --text-faint: #94a3b8;
      --accent: #2563eb;
      --accent-hover: #1d4ed8;
      --accent-glow: rgba(37, 99, 235, 0.2);

      --card-shadow: 0 1px 3px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.04);
      --card-shadow-hover: 0 10px 20px rgba(0, 0, 0, 0.1), 0 3px 6px rgba(0, 0, 0, 0.05);
      --drop-placeholder-bg: rgba(37, 99, 235, 0.08);
      --drop-placeholder-border: #2563eb;

      --p-high-bg: #fee2e2;
      --p-high-text: #991b1b;
      --p-high-dot: #dc2626;

      --p-med-bg: #fef3c7;
      --p-med-text: #92400e;
      --p-med-dot: #d97706;

      --p-low-bg: #e0f2fe;
      --p-low-text: #075985;
      --p-low-dot: #0284c7;

      --col-todo: #0284c7;
      --col-progress: #d97706;
      --col-done: #059669;
    }

    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }

    body {
      font-family: var(--font-sans);
      background-color: var(--bg-canvas);
      color: var(--text-main);
      height: 100vh;
      overflow: hidden;
      display: flex;
      flex-direction: column;
      transition: background-color 0.2s ease, color 0.2s ease;
      -webkit-font-smoothing: antialiased;
    }

    /* Top Navigation Bar */
    .app-header {
      flex: 0 0 auto;
      height: 64px;
      background-color: var(--bg-header);
      border-bottom: 1px solid var(--border-subtle);
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 0 24px;
      gap: 16px;
      z-index: 10;
    }

    .brand-group {
      display: flex;
      align-items: center;
      gap: 12px;
      user-select: none;
    }

    .brand-icon {
      width: 32px;
      height: 32px;
      border-radius: 8px;
      background: linear-gradient(135deg, #3b82f6, #6366f1);
      display: flex;
      align-items: center;
      justify-content: center;
      color: #fff;
      box-shadow: 0 2px 8px var(--accent-glow);
    }

    .brand-name {
      font-size: 1.15rem;
      font-weight: 700;
      letter-spacing: -0.02em;
      color: var(--text-main);
    }

    .brand-badge {
      font-size: 0.72rem;
      font-weight: 600;
      background: var(--border-subtle);
      color: var(--text-muted);
      padding: 2px 8px;
      border-radius: 12px;
    }

    .header-actions {
      display: flex;
      align-items: center;
      gap: 12px;
      flex: 1;
      justify-content: flex-end;
      max-width: 720px;
    }

    /* Search Box */
    .search-wrapper {
      position: relative;
      flex: 1;
      max-width: 320px;
    }

    .search-icon {
      position: absolute;
      left: 12px;
      top: 50%;
      transform: translateY(-50%);
      color: var(--text-muted);
      pointer-events: none;
      display: flex;
    }

    .search-input {
      width: 100%;
      height: 38px;
      padding: 0 34px 0 36px;
      background-color: var(--bg-canvas);
      border: 1px solid var(--border-subtle);
      border-radius: 8px;
      color: var(--text-main);
      font-family: inherit;
      font-size: 0.88rem;
      transition: all 0.15s ease;
      outline: none;
    }

    .search-input:focus {
      border-color: var(--accent);
      box-shadow: 0 0 0 3px var(--accent-glow);
    }

    .search-clear-btn {
      position: absolute;
      right: 10px;
      top: 50%;
      transform: translateY(-50%);
      background: transparent;
      border: none;
      color: var(--text-muted);
      cursor: pointer;
      display: none;
      align-items: center;
      justify-content: center;
      padding: 4px;
      border-radius: 4px;
    }

    .search-clear-btn:hover {
      color: var(--text-main);
    }

    .search-clear-btn.visible {
      display: flex;
    }

    /* Buttons */
    .btn {
      height: 38px;
      padding: 0 16px;
      border-radius: 8px;
      font-family: inherit;
      font-size: 0.88rem;
      font-weight: 600;
      display: inline-flex;
      align-items: center;
      gap: 8px;
      cursor: pointer;
      border: 1px solid transparent;
      transition: all 0.15s ease;
      user-select: none;
      white-space: nowrap;
    }

    .btn:focus-visible {
      outline: 2px solid var(--accent);
      outline-offset: 2px;
    }

    .btn-primary {
      background-color: var(--accent);
      color: #ffffff;
    }

    .btn-primary:hover {
      background-color: var(--accent-hover);
    }

    .btn-secondary {
      background-color: var(--bg-canvas);
      border-color: var(--border-subtle);
      color: var(--text-main);
    }

    .btn-secondary:hover {
      background-color: var(--bg-card);
      border-color: var(--border-strong);
    }

    .btn-icon-only {
      width: 38px;
      height: 38px;
      padding: 0;
      justify-content: center;
    }

    /* Kanban Board Layout */
    .kanban-board {
      flex: 1 1 auto;
      display: flex;
      gap: 20px;
      padding: 24px;
      overflow-x: auto;
      overflow-y: hidden;
      min-height: 0;
    }

    .kanban-column {
      flex: 1 1 0;
      min-width: 300px;
      max-width: 440px;
      background-color: var(--bg-column);
      border: 1px solid var(--border-subtle);
      border-radius: 12px;
      display: flex;
      flex-direction: column;
      max-height: 100%;
      transition: border-color 0.15s ease;
    }

    .column-header {
      padding: 14px 16px;
      border-bottom: 1px solid var(--border-subtle);
      display: flex;
      align-items: center;
      justify-content: space-between;
      user-select: none;
    }

    .col-title-group {
      display: flex;
      align-items: center;
      gap: 10px;
    }

    .col-dot {
      width: 10px;
      height: 10px;
      border-radius: 50%;
    }

    .col-dot.todo { background-color: var(--col-todo); }
    .col-dot.in-progress { background-color: var(--col-progress); }
    .col-dot.done { background-color: var(--col-done); }

    .col-title {
      font-size: 0.95rem;
      font-weight: 700;
      color: var(--text-main);
      letter-spacing: -0.01em;
    }

    .col-count {
      font-size: 0.75rem;
      font-weight: 700;
      background-color: var(--bg-canvas);
      color: var(--text-muted);
      padding: 2px 8px;
      border-radius: 10px;
      border: 1px solid var(--border-subtle);
    }

    .col-add-btn {
      background: transparent;
      border: none;
      color: var(--text-muted);
      cursor: pointer;
      width: 28px;
      height: 28px;
      border-radius: 6px;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: all 0.15s ease;
    }

    .col-add-btn:hover {
      background-color: var(--bg-card);
      color: var(--text-main);
    }

    /* Cards Container */
    .column-cards {
      flex: 1 1 auto;
      overflow-y: auto;
      padding: 12px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      min-height: 120px;
    }

    /* Kanban Card */
    .kanban-card {
      background-color: var(--bg-card);
      border: 1px solid var(--border-subtle);
      border-radius: 10px;
      padding: 14px 16px;
      box-shadow: var(--card-shadow);
      cursor: grab;
      position: relative;
      transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease, opacity 0.15s ease;
      user-select: none;
    }

    .kanban-card:hover {
      box-shadow: var(--card-shadow-hover);
      border-color: var(--border-strong);
      transform: translateY(-2px);
    }

    .kanban-card:active {
      cursor: grabbing;
    }

    .kanban-card.is-dragging {
      opacity: 0.35;
      transform: scale(0.98);
      border-style: dashed;
    }

    .kanban-card.is-deleting {
      transform: scale(0.8);
      opacity: 0;
      max-height: 0;
      padding-top: 0;
      padding-bottom: 0;
      margin-top: 0;
      margin-bottom: 0;
      overflow: hidden;
      border-width: 0;
      transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    }

    .card-top {
      display: flex;
      align-items: center;
      justify-content: space-between;
      margin-bottom: 10px;
    }

    .card-meta-left {
      display: flex;
      align-items: center;
      gap: 8px;
    }

    .card-code {
      font-family: var(--font-mono);
      font-size: 0.72rem;
      font-weight: 600;
      color: var(--text-faint);
      letter-spacing: 0.02em;
    }

    /* Priority Badges */
    .priority-badge {
      display: inline-flex;
      align-items: center;
      gap: 5px;
      padding: 2px 7px;
      border-radius: 5px;
      font-size: 0.7rem;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.03em;
    }

    .priority-badge .dot {
      width: 6px;
      height: 6px;
      border-radius: 50%;
    }

    .priority-high {
      background-color: var(--p-high-bg);
      color: var(--p-high-text);
    }
    .priority-high .dot { background-color: var(--p-high-dot); }

    .priority-medium {
      background-color: var(--p-med-bg);
      color: var(--p-med-text);
    }
    .priority-medium .dot { background-color: var(--p-med-dot); }

    .priority-low {
      background-color: var(--p-low-bg);
      color: var(--p-low-text);
    }
    .priority-low .dot { background-color: var(--p-low-dot); }

    /* Delete Button */
    .card-delete-btn {
      background: transparent;
      border: none;
      color: var(--text-faint);
      cursor: pointer;
      width: 24px;
      height: 24px;
      border-radius: 4px;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: all 0.15s ease;
    }

    .card-delete-btn:hover {
      background-color: rgba(239, 68, 68, 0.15);
      color: #ef4444;
    }

    .card-title {
      font-size: 0.92rem;
      font-weight: 600;
      line-height: 1.4;
      color: var(--text-main);
      margin-bottom: 12px;
      word-break: break-word;
    }

    .card-bottom {
      display: flex;
      align-items: center;
      justify-content: space-between;
      font-size: 0.75rem;
      color: var(--text-muted);
      border-top: 1px solid var(--border-subtle);
      padding-top: 10px;
    }

    .card-tag {
      background-color: var(--bg-canvas);
      padding: 2px 8px;
      border-radius: 4px;
      border: 1px solid var(--border-subtle);
      font-weight: 500;
    }

    .card-grip {
      color: var(--text-faint);
      display: flex;
      align-items: center;
    }

    /* Drop Indicator */
    .drop-placeholder {
      border: 2px dashed var(--drop-placeholder-border);
      background-color: var(--drop-placeholder-bg);
      border-radius: 10px;
      min-height: 72px;
      display: flex;
      align-items: center;
      justify-content: center;
      color: var(--drop-placeholder-border);
      font-size: 0.82rem;
      font-weight: 600;
      pointer-events: none;
      animation: pulseDrop 1.2s infinite alternate ease-in-out;
      margin: 2px 0;
    }

    @keyframes pulseDrop {
      0% { opacity: 0.6; transform: scale(0.99); }
      100% { opacity: 1; transform: scale(1); }
    }

    /* Empty Column State */
    .column-empty {
      border: 1px dashed var(--border-strong);
      border-radius: 8px;
      padding: 24px 16px;
      text-align: center;
      color: var(--text-muted);
      font-size: 0.84rem;
      user-select: none;
      margin: auto 0;
    }

    .column-empty span {
      display: block;
      margin-top: 4px;
      font-size: 0.75rem;
      color: var(--text-faint);
    }

    /* Modal Form */
    .modal-overlay {
      position: fixed;
      inset: 0;
      background-color: rgba(0, 0, 0, 0.65);
      backdrop-filter: blur(4px);
      display: flex;
      align-items: center;
      justify-content: center;
      padding: 16px;
      z-index: 100;
      opacity: 0;
      visibility: hidden;
      transition: opacity 0.2s ease, visibility 0.2s ease;
    }

    .modal-overlay.open {
      opacity: 1;
      visibility: visible;
    }

    .modal-dialog {
      background-color: var(--bg-card);
      border: 1px solid var(--border-strong);
      border-radius: 14px;
      width: 100%;
      max-width: 460px;
      box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
      transform: scale(0.95);
      transition: transform 0.2s ease;
      overflow: hidden;
    }

    .modal-overlay.open .modal-dialog {
      transform: scale(1);
    }

    .modal-header {
      padding: 18px 20px;
      border-bottom: 1px solid var(--border-subtle);
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    .modal-title {
      font-size: 1.05rem;
      font-weight: 700;
      color: var(--text-main);
    }

    .modal-close-btn {
      background: transparent;
      border: none;
      color: var(--text-muted);
      cursor: pointer;
      display: flex;
      padding: 4px;
      border-radius: 6px;
    }

    .modal-close-btn:hover {
      color: var(--text-main);
      background-color: var(--bg-canvas);
    }

    .modal-body {
      padding: 20px;
      display: flex;
      flex-direction: column;
      gap: 16px;
    }

    .form-group {
      display: flex;
      flex-direction: column;
      gap: 6px;
    }

    .form-label {
      font-size: 0.8rem;
      font-weight: 600;
      color: var(--text-muted);
      text-transform: uppercase;
      letter-spacing: 0.04em;
    }

    .form-input, .form-select {
      width: 100%;
      height: 40px;
      padding: 0 12px;
      background-color: var(--bg-canvas);
      border: 1px solid var(--border-subtle);
      border-radius: 8px;
      color: var(--text-main);
      font-family: inherit;
      font-size: 0.9rem;
      outline: none;
      transition: border-color 0.15s ease, box-shadow 0.15s ease;
    }

    .form-input:focus, .form-select:focus {
      border-color: var(--accent);
      box-shadow: 0 0 0 3px var(--accent-glow);
    }

    .form-input.error {
      border-color: #ef4444;
      box-shadow: 0 0 0 3px rgba(239, 68, 68, 0.2);
    }

    .form-error-msg {
      font-size: 0.75rem;
      color: #ef4444;
      display: none;
      margin-top: 2px;
    }

    .form-error-msg.visible {
      display: block;
    }

    /* Priority Pills Selector */
    .priority-selector {
      display: grid;
      grid-template-columns: repeat(3, 1fr);
      gap: 8px;
    }

    .priority-opt-btn {
      height: 38px;
      border-radius: 8px;
      border: 1px solid var(--border-subtle);
      background-color: var(--bg-canvas);
      color: var(--text-muted);
      font-family: inherit;
      font-size: 0.82rem;
      font-weight: 600;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 6px;
      transition: all 0.15s ease;
    }

    .priority-opt-btn:hover {
      border-color: var(--border-strong);
      color: var(--text-main);
    }

    .priority-opt-btn.active[data-priority="low"] {
      background-color: var(--p-low-bg);
      border-color: var(--p-low-dot);
      color: var(--p-low-text);
    }

    .priority-opt-btn.active[data-priority="medium"] {
      background-color: var(--p-med-bg);
      border-color: var(--p-med-dot);
      color: var(--p-med-text);
    }

    .priority-opt-btn.active[data-priority="high"] {
      background-color: var(--p-high-bg);
      border-color: var(--p-high-dot);
      color: var(--p-high-text);
    }

    .modal-footer {
      padding: 16px 20px;
      background-color: var(--bg-canvas);
      border-top: 1px solid var(--border-subtle);
      display: flex;
      align-items: center;
      justify-content: flex-end;
      gap: 10px;
    }

    /* Responsive Queries */
    @media (max-width: 860px) {
      body {
        height: auto;
        min-height: 100vh;
        overflow-y: auto;
        overflow-x: hidden;
      }

      .app-header {
        height: auto;
        padding: 14px 16px;
        flex-direction: column;
        align-items: stretch;
        gap: 12px;
      }

      .brand-group {
        justify-content: space-between;
      }

      .header-actions {
        max-width: none;
        justify-content: stretch;
      }

      .search-wrapper {
        max-width: none;
      }

      .kanban-board {
        flex-direction: column;
        overflow: visible;
        padding: 16px;
        gap: 20px;
      }

      .kanban-column {
        max-width: 100%;
        min-width: 0;
      }

      .column-cards {
        max-height: none;
        overflow: visible;
      }
    }
  </style>
</head>
<body>

  <!-- Top Navigation -->
  <header class="app-header">
    <div class="brand-group">
      <div style="display:flex; align-items:center; gap:10px;">
        <div class="brand-icon">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
            <rect x="3" y="3" width="18" height="18" rx="2"/>
            <path d="M9 3v18"/>
            <path d="M15 3v18"/>
          </svg>
        </div>
        <span class="brand-name">Kanban Flow</span>
      </div>
      <span class="brand-badge" id="totalTasksBadge">6 Tasks</span>
    </div>

    <div class="header-actions">
      <!-- Search -->
      <div class="search-wrapper">
        <span class="search-icon">
          <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round">
            <circle cx="11" cy="11" r="8"/>
            <line x1="21" y1="21" x2="16.65" y2="16.65"/>
          </svg>
        </span>
        <input type="text" id="searchInput" class="search-input" placeholder="Search tasks by title..." autocomplete="off">
        <button id="searchClearBtn" class="search-clear-btn" title="Clear search">
          <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
            <line x1="18" y1="6" x2="6" y2="18"/>
            <line x1="6" y1="6" x2="18" y2="18"/>
          </svg>
        </button>
      </div>

      <!-- Add Card Button -->
      <button id="openAddModalBtn" class="btn btn-primary" title="Create new task">
        <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
          <line x1="12" y1="5" x2="12" y2="19"/>
          <line x1="5" y1="12" x2="19" y2="12"/>
        </svg>
        <span>Add Task</span>
      </button>

      <!-- Theme Switcher -->
      <button id="themeToggleBtn" class="btn btn-secondary btn-icon-only" title="Toggle theme">
        <svg id="themeIconSun" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
          <circle cx="12" cy="12" r="5"/>
          <line x1="12" y1="1" x2="12" y2="3"/>
          <line x1="12" y1="21" x2="12" y2="23"/>
          <line x1="4.22" y1="4.22" x2="5.64" y2="5.64"/>
          <line x1="18.36" y1="18.36" x2="19.78" y2="19.78"/>
          <line x1="1" y1="12" x2="3" y2="12"/>
          <line x1="21" y1="12" x2="23" y2="12"/>
          <line x1="4.22" y1="19.78" x2="5.64" y2="18.36"/>
          <line x1="18.36" y1="5.64" x2="19.78" y2="4.22"/>
        </svg>
        <svg id="themeIconMoon" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="display:none;">
          <path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"/>
        </svg>
      </button>
    </div>
  </header>

  <!-- Board Container -->
  <main class="kanban-board">
    <!-- To Do Column -->
    <section class="kanban-column" data-column="todo">
      <header class="column-header">
        <div class="col-title-group">
          <span class="col-dot todo"></span>
          <h2 class="col-title">To do</h2>
          <span class="col-count" id="count-todo">0</span>
        </div>
        <button class="col-add-btn" data-add-to="todo" title="Add task to To do">
          <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
            <line x1="12" y1="5" x2="12" y2="19"/>
            <line x1="5" y1="12" x2="19" y2="12"/>
          </svg>
        </button>
      </header>
      <div class="column-cards" id="cards-todo" data-column="todo"></div>
    </section>

    <!-- In Progress Column -->
    <section class="kanban-column" data-column="in-progress">
      <header class="column-header">
        <div class="col-title-group">
          <span class="col-dot in-progress"></span>
          <h2 class="col-title">In progress</h2>
          <span class="col-count" id="count-in-progress">0</span>
        </div>
        <button class="col-add-btn" data-add-to="in-progress" title="Add task to In progress">
          <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
            <line x1="12" y1="5" x2="12" y2="19"/>
            <line x1="5" y1="12" x2="19" y2="12"/>
          </svg>
        </button>
      </header>
      <div class="column-cards" id="cards-in-progress" data-column="in-progress"></div>
    </section>

    <!-- Done Column -->
    <section class="kanban-column" data-column="done">
      <header class="column-header">
        <div class="col-title-group">
          <span class="col-dot done"></span>
          <h2 class="col-title">Done</h2>
          <span class="col-count" id="count-done">0</span>
        </div>
        <button class="col-add-btn" data-add-to="done" title="Add task to Done">
          <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.5" stroke-linecap="round" stroke-linejoin="round">
            <line x1="12" y1="5" x2="12" y2="19"/>
            <line x1="5" y1="12" x2="19" y2="12"/>
          </svg>
        </button>
      </header>
      <div class="column-cards" id="cards-done" data-column="done"></div>
    </section>
  </main>

  <!-- Add Card Modal Dialog -->
  <div class="modal-overlay" id="addCardModal" role="dialog" aria-modal="true" aria-labelledby="modalHeading">
    <div class="modal-dialog">
      <header class="modal-header">
        <h3 class="modal-title" id="modalHeading">Create New Task</h3>
        <button type="button" class="modal-close-btn" id="modalCloseBtn" aria-label="Close modal">
          <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
            <line x1="18" y1="6" x2="6" y2="18"/>
            <line x1="6" y1="6" x2="18" y2="18"/>
          </svg>
        </button>
      </header>

      <form id="addCardForm" autocomplete="off">
        <div class="modal-body">
          <div class="form-group">
            <label class="form-label" for="taskTitleInput">Task Title *</label>
            <input type="text" id="taskTitleInput" class="form-input" placeholder="e.g. Audit database query latency" maxlength="120" required>
            <span class="form-error-msg" id="taskTitleError">Title is required.</span>
          </div>

          <div class="form-group">
            <label class="form-label">Priority</label>
            <div class="priority-selector" id="prioritySelector">
              <button type="button" class="priority-opt-btn" data-priority="low">
                <span class="dot" style="width:6px; height:6px; border-radius:50%; background:#0ea5e9;"></span>
                Low
              </button>
              <button type="button" class="priority-opt-btn active" data-priority="medium">
                <span class="dot" style="width:6px; height:6px; border-radius:50%; background:#f59e0b;"></span>
                Medium
              </button>
              <button type="button" class="priority-opt-btn" data-priority="high">
                <span class="dot" style="width:6px; height:6px; border-radius:50%; background:#ef4444;"></span>
                High
              </button>
            </div>
          </div>

          <div class="form-group">
            <label class="form-label" for="taskColSelect">Column</label>
            <select id="taskColSelect" class="form-select">
              <option value="todo">To do</option>
              <option value="in-progress">In progress</option>
              <option value="done">Done</option>
            </select>
          </div>

          <div class="form-group">
            <label class="form-label" for="taskTagInput">Tag / Category</label>
            <input type="text" id="taskTagInput" class="form-input" placeholder="e.g. Backend, UI, Security" maxlength="24">
          </div>
        </div>

        <footer class="modal-footer">
          <button type="button" class="btn btn-secondary" id="modalCancelBtn">Cancel</button>
          <button type="submit" class="btn btn-primary">Create Task</button>
        </footer>
      </form>
    </div>
  </div>

  <script>
    /* In-Memory Kanban State (No storage APIs used) */
    const state = {
      theme: 'dark',
      searchQuery: '',
      selectedPriority: 'medium',
      counter: 107,
      columns: {
        'todo': [
          {
            id: 'card-1',
            code: 'DEV-101',
            title: 'Audit database indexes for query latency & slow scans',
            priority: 'high',
            tag: 'Backend'
          },
          {
            id: 'card-2',
            code: 'DEV-102',
            title: 'Update OAuth2 consent screen branding & terms',
            priority: 'low',
            tag: 'Security'
          }
        ],
        'in-progress': [
          {
            id: 'card-3',
            code: 'DEV-103',
            title: 'Build drag and drop column reordering with visual guide',
            priority: 'high',
            tag: 'Frontend'
          },
          {
            id: 'card-4',
            code: 'DEV-104',
            title: 'Implement accessible design token system for dark mode',
            priority: 'medium',
            tag: 'Design'
          }
        ],
        'done': [
          {
            id: 'card-5',
            code: 'DEV-105',
            title: 'Draft RFC for real-time websocket synchronization',
            priority: 'medium',
            tag: 'Core'
          },
          {
            id: 'card-6',
            code: 'DEV-106',
            title: 'Configure automated CI smoke test pipeline in GitHub Actions',
            priority: 'low',
            tag: 'DevOps'
          }
        ]
      }
    };

    /* Drag & Drop Runtime Tracker */
    let draggedCardId = null;
    const dropPlaceholder = document.createElement('div');
    dropPlaceholder.className = 'drop-placeholder';
    dropPlaceholder.textContent = 'Drop task here';

    /* DOM Elements */
    const searchInput = document.getElementById('searchInput');
    const searchClearBtn = document.getElementById('searchClearBtn');
    const openAddModalBtn = document.getElementById('openAddModalBtn');
    const themeToggleBtn = document.getElementById('themeToggleBtn');
    const themeIconSun = document.getElementById('themeIconSun');
    const themeIconMoon = document.getElementById('themeIconMoon');
    const addCardModal = document.getElementById('addCardModal');
    const modalCloseBtn = document.getElementById('modalCloseBtn');
    const modalCancelBtn = document.getElementById('modalCancelBtn');
    const addCardForm = document.getElementById('addCardForm');
    const taskTitleInput = document.getElementById('taskTitleInput');
    const taskTitleError = document.getElementById('taskTitleError');
    const taskColSelect = document.getElementById('taskColSelect');
    const taskTagInput = document.getElementById('taskTagInput');
    const prioritySelector = document.getElementById('prioritySelector');
    const totalTasksBadge = document.getElementById('totalTasksBadge');

    /* Theme Toggle */
    function updateThemeUI() {
      document.documentElement.setAttribute('data-theme', state.theme);
      if (state.theme === 'dark') {
        themeIconSun.style.display = 'block';
        themeIconMoon.style.display = 'none';
      } else {
        themeIconSun.style.display = 'none';
        themeIconMoon.style.display = 'block';
      }
    }

    themeToggleBtn.addEventListener('click', () => {
      state.theme = state.theme === 'dark' ? 'light' : 'dark';
      updateThemeUI();
    });

    /* Priority Selector in Modal */
    prioritySelector.addEventListener('click', (e) => {
      const btn = e.target.closest('.priority-opt-btn');
      if (!btn) return;
      prioritySelector.querySelectorAll('.priority-opt-btn').forEach(b => b.classList.remove('active'));
      btn.classList.add('active');
      state.selectedPriority = btn.dataset.priority;
    });

    /* Modal Controls */
    function openModal(defaultColumn = 'todo') {
      taskTitleInput.value = '';
      taskTagInput.value = '';
      taskTitleInput.classList.remove('error');
      taskTitleError.classList.remove('visible');
      taskColSelect.value = defaultColumn;
      state.selectedPriority = 'medium';

      prioritySelector.querySelectorAll('.priority-opt-btn').forEach(b => {
        b.classList.toggle('active', b.dataset.priority === 'medium');
      });

      addCardModal.classList.add('open');
      setTimeout(() => taskTitleInput.focus(), 50);
    }

    function closeModal() {
      addCardModal.classList.remove('open');
    }

    openAddModalBtn.addEventListener('click', () => openModal('todo'));
    modalCloseBtn.addEventListener('click', closeModal);
    modalCancelBtn.addEventListener('click', closeModal);

    addCardModal.addEventListener('click', (e) => {
      if (e.target === addCardModal) {
        closeModal();
      }
    });

    window.addEventListener('keydown', (e) => {
      if (e.key === 'Escape' && addCardModal.classList.contains('open')) {
        closeModal();
      }
    });

    /* Column quick-add buttons */
    document.querySelectorAll('[data-add-to]').forEach(btn => {
      btn.addEventListener('click', () => {
        openModal(btn.dataset.addTo);
      });
    });

    /* Form Submit (Create Card) */
    addCardForm.addEventListener('submit', (e) => {
      e.preventDefault();
      const title = taskTitleInput.value.trim();

      if (!title) {
        taskTitleInput.classList.add('error');
        taskTitleError.classList.add('visible');
        taskTitleInput.focus();
        return;
      }

      const column = taskColSelect.value;
      const tag = taskTagInput.value.trim() || 'General';
      const newCard = {
        id: 'card-' + Date.now(),
        code: 'DEV-' + (state.counter++),
        title: title,
        priority: state.selectedPriority,
        tag: tag
      };

      state.columns[column].unshift(newCard);
      closeModal();
      render();
    });

    taskTitleInput.addEventListener('input', () => {
      if (taskTitleInput.value.trim()) {
        taskTitleInput.classList.remove('error');
        taskTitleError.classList.remove('visible');
      }
    });

    /* Delete Card Function */
    window.deleteCard = function(cardId) {
      const cardEl = document.querySelector(`.kanban-card[data-id="${cardId}"]`);
      if (cardEl) {
        cardEl.classList.add('is-deleting');
        setTimeout(() => {
          performDelete(cardId);
        }, 180);
      } else {
        performDelete(cardId);
      }
    };

    function performDelete(cardId) {
      for (const colKey of Object.keys(state.columns)) {
        const idx = state.columns[colKey].findIndex(c => c.id === cardId);
        if (idx !== -1) {
          state.columns[colKey].splice(idx, 1);
          break;
        }
      }
      render();
    }

    /* Move Card within State */
    function moveCard(cardId, targetCol, targetIndex) {
      let sourceCol = null;
      let sourceIdx = -1;
      let cardObj = null;

      for (const colKey of Object.keys(state.columns)) {
        const idx = state.columns[colKey].findIndex(c => c.id === cardId);
        if (idx !== -1) {
          sourceCol = colKey;
          sourceIdx = idx;
          cardObj = state.columns[colKey][idx];
          break;
        }
      }

      if (!cardObj) return;

      if (sourceCol === targetCol) {
        if (sourceIdx === targetIndex || sourceIdx === targetIndex - 1) {
          render();
          return;
        }
        state.columns[sourceCol].splice(sourceIdx, 1);
        const adjustedIdx = sourceIdx < targetIndex ? targetIndex - 1 : targetIndex;
        state.columns[targetCol].splice(adjustedIdx, 0, cardObj);
      } else {
        state.columns[sourceCol].splice(sourceIdx, 1);
        state.columns[targetCol].splice(targetIndex, 0, cardObj);
      }

      render();
    }

    /* Live Search Filter */
    searchInput.addEventListener('input', () => {
      state.searchQuery = searchInput.value.trim().toLowerCase();
      searchClearBtn.classList.toggle('visible', state.searchQuery.length > 0);
      render();
    });

    searchClearBtn.addEventListener('click', () => {
      searchInput.value = '';
      state.searchQuery = '';
      searchClearBtn.classList.remove('visible');
      searchInput.focus();
      render();
    });

    /* Calculate Drop Target Position */
    function getDropTarget(container, y) {
      const cards = [...container.querySelectorAll('.kanban-card:not(.is-dragging)')];
      let closestCard = null;
      let closestOffset = Number.NEGATIVE_INFINITY;

      for (const card of cards) {
        const box = card.getBoundingClientRect();
        const offset = y - box.top - box.height / 2;
        if (offset < 0 && offset > closestOffset) {
          closestOffset = offset;
          closestCard = card;
        }
      }
      return closestCard;
    }

    /* Card Drag & Drop Wireup */
    function wireCardDrag(cardEl) {
      cardEl.addEventListener('dragstart', (e) => {
        draggedCardId = cardEl.dataset.id;
        e.dataTransfer.setData('text/plain', cardEl.dataset.id);
        e.dataTransfer.effectAllowed = 'move';
        setTimeout(() => {
          cardEl.classList.add('is-dragging');
        }, 0);
      });

      cardEl.addEventListener('dragend', () => {
        cardEl.classList.remove('is-dragging');
        draggedCardId = null;
        if (dropPlaceholder.parentNode) {
          dropPlaceholder.parentNode.removeChild(dropPlaceholder);
        }
      });
    }

    /* Setup Column Containers for Drop */
    document.querySelectorAll('.column-cards').forEach(container => {
      container.addEventListener('dragover', (e) => {
        e.preventDefault();
        e.dataTransfer.dropEffect = 'move';

        const afterElement = getDropTarget(container, e.clientY);
        if (afterElement == null) {
          if (dropPlaceholder.nextSibling !== null || dropPlaceholder.parentNode !== container) {
            container.appendChild(dropPlaceholder);
          }
        } else {
          if (dropPlaceholder.nextSibling !== afterElement) {
            container.insertBefore(dropPlaceholder, afterElement);
          }
        }
      });

      container.addEventListener('drop', (e) => {
        e.preventDefault();
        const cardId = e.dataTransfer.getData('text/plain') || draggedCardId;
        if (!cardId) return;

        const targetColumn = container.dataset.column;
        let targetIndex = state.columns[targetColumn].length;

        if (dropPlaceholder.parentNode === container && dropPlaceholder.nextElementSibling) {
          const nextId = dropPlaceholder.nextElementSibling.dataset.id;
          if (nextId) {
            const idx = state.columns[targetColumn].findIndex(c => c.id === nextId);
            if (idx !== -1) {
              targetIndex = idx;
            }
          }
        }

        if (dropPlaceholder.parentNode) {
          dropPlaceholder.parentNode.removeChild(dropPlaceholder);
        }

        moveCard(cardId, targetColumn, targetIndex);
      });
    });

    /* Escape HTML utility */
    function escapeHtml(str) {
      return String(str)
        .replace(/&/g, '&amp;')
        .replace(/</g, '&lt;')
        .replace(/>/g, '&gt;')
        .replace(/"/g, '&quot;')
        .replace(/'/g, '&#39;');
    }

    /* Main Render Function */
    function render() {
      let totalVisible = 0;
      let totalOverall = 0;

      const colKeys = ['todo', 'in-progress', 'done'];

      colKeys.forEach(colKey => {
        const container = document.getElementById(`cards-${colKey}`);
        const countBadge = document.getElementById(`count-${colKey}`);
        const allCards = state.columns[colKey];
        totalOverall += allCards.length;

        // Filter cards by search query
        const visibleCards = state.searchQuery
          ? allCards.filter(c => c.title.toLowerCase().includes(state.searchQuery))
          : allCards;

        totalVisible += visibleCards.length;

        // Update column count badge
        if (state.searchQuery) {
          countBadge.textContent = `${visibleCards.length}/${allCards.length}`;
        } else {
          countBadge.textContent = allCards.length;
        }

        // Render card elements
        if (visibleCards.length === 0) {
          container.innerHTML = `
            <div class="column-empty">
              ${state.searchQuery ? 'No matching tasks' : 'No tasks in this column'}
              <span>${state.searchQuery ? 'Try another search query' : 'Click + to add a task'}</span>
            </div>
          `;
        } else {
          container.innerHTML = visibleCards.map(card => {
            const safeTitle = escapeHtml(card.title);
            const safeTag = escapeHtml(card.tag);
            const safeCode = escapeHtml(card.code);
            const priorityClass = `priority-${card.priority}`;
            const priorityLabel = card.priority;

            return `
              <article class="kanban-card" draggable="true" data-id="${card.id}">
                <div class="card-top">
                  <div class="card-meta-left">
                    <span class="card-code">${safeCode}</span>
                    <span class="priority-badge ${priorityClass}">
                      <span class="dot"></span>
                      ${priorityLabel}
                    </span>
                  </div>
                  <button type="button" class="card-delete-btn" title="Delete task" aria-label="Delete task ${safeCode}" onclick="deleteCard('${card.id}')" draggable="false">
                    <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2.2" stroke-linecap="round" stroke-linejoin="round">
                      <path d="M3 6h18"/>
                      <path d="M19 6v14a2 2 0 0 1-2 2H7a2 2 0 0 1-2-2V6"/>
                      <path d="M8 6V4a2 2 0 0 1 2-2h4a2 2 0 0 1 2 2v2"/>
                      <line x1="10" y1="11" x2="10" y2="17"/>
                      <line x1="14" y1="11" x2="14" y2="17"/>
                    </svg>
                  </button>
                </div>
                <h3 class="card-title">${safeTitle}</h3>
                <div class="card-bottom">
                  <span class="card-tag">${safeTag}</span>
                  <span class="card-grip" title="Drag to move">
                    <svg width="12" height="12" viewBox="0 0 24 24" fill="currentColor">
                      <circle cx="9" cy="6" r="2"/>
                      <circle cx="15" cy="6" r="2"/>
                      <circle cx="9" cy="12" r="2"/>
                      <circle cx="15" cy="12" r="2"/>
                      <circle cx="9" cy="18" r="2"/>
                      <circle cx="15" cy="18" r="2"/>
                    </svg>
                  </span>
                </div>
              </article>
            `;
          }).join('');

          // Wire drag handlers to newly rendered cards
          container.querySelectorAll('.kanban-card').forEach(wireCardDrag);
        }
      });

      // Update total badge in header
      if (state.searchQuery) {
        totalTasksBadge.textContent = `${totalVisible} of ${totalOverall} Tasks`;
      } else {
        totalTasksBadge.textContent = `${totalOverall} Tasks`;
      }
    }

    /* Initialize Application */
    updateThemeUI();
    render();
  </script>
</body>
</html>
Reasoning trace (18,044 tokens)
**Structuring Interactive Kanban**

I'm focused on architecting the core structure for an interactive Kanban board using only vanilla HTML, CSS, and JavaScript. My current thoughts revolve around setting up the three essential columns – "To do", "In progress", and "Done" – and planning how to dynamically display the card count within each. I'm also considering the initial placement of six realistic cards to give the board a populated and active feel from the start.

**Developing Dynamic Features**

My current focus is on implementing interactive features. I'm planning the logic for adding new cards via a modal, including basic validation, and the deletion of existing cards. The search functionality to filter cards by title is also a key area of my thought process right now.

**Designing Board Components**

I'm currently detailing the visual and functional elements for the Kanban board. My thoughts are on the layout of columns with their titles, colored indicators, and card count pills, as well as how to best present the individual cards with their titles, metadata, and priority badges. I'm also planning the subtle interactive elements like drop indicators and delete buttons.

**Implementing Drag-and-Drop**

I'm refining the drag-and-drop mechanism, ensuring smooth animations and accessible touch support. My thoughts are prioritizing the use of native HTML5 drag and drop for robust functionality and considering the visual cues like drop indicators and dragging states. The modal for card creation is also being fleshed out with accessibility and user-friendliness in mind.

**Filtering Visible Cards**

My thoughts are now honing in on the live filtering of cards as a user types into the search input. I'm considering how best to visually indicate non-matching cards, perhaps by hiding them with a subtle animation, and how to dynamically update the column counters to reflect this filtered view.

**Populating Initial State**

I'm confirming the immediate rendering of six pre-populated cards on load, styled inline via CSS and JavaScript, with specific details like IDs, titles, priorities, tags, and due dates for each, all within the "To Do", "In Progress", and "Done" columns.

**Styling Card Elements**

I'm solidifying the visual design, specifically focusing on how priorities will be styled across both light and dark themes. This involves defining distinct background, text, and dot colors for High, Medium, and Low priorities, ensuring a clear and accessible visual hierarchy for each card.

**Defining Theme Variables**

I'm solidifying the CSS variables for both light and dark themes, establishing the aesthetic foundation. My thoughts are currently focused on finalizing color palettes for backgrounds, borders, and text, ensuring consistency and accessibility across all UI elements. I'm also refining shadow and drop zone visual properties.

**Visualizing Drop Targets**

I'm examining how to best implement a visual drop indicator. My current thoughts are on creating a dedicated element that dynamically positions itself to show where a dragged card will land, ensuring clarity during reordering. I'm also considering the algorithm to determine the precise insertion point within a column.

**Implementing Drop Logic**

I'm finalizing the core drag-and-drop logic, specifically focusing on the `drop` function. My current thoughts involve accurately identifying the target column and insertion index based on the drop indicator's position, updating the state array, and then re-rendering the columns to reflect the change. I'm also addressing the clean-up after a drag ends.

**Improving Drop Indicator**

I'm refining the visual feedback for drop targets. My thoughts are leaning towards a dynamic dashed slot, roughly 64px high, with circular ends for clear visual guidance, akin to established platforms. I'm also considering the details of the modal for adding new cards, including its form elements and validation logic.

**Refining Card Interactions**

I'm solidifying the card interaction logic, focusing on how deleting a card will be handled without browser prompts, opting for a smooth visual removal and state update. The search functionality is also being refined for live, case-insensitive filtering by card title.

**Refining Search and Theme**

I'm enhancing the search functionality to include live, case-insensitive filtering across titles, tags, and descriptions. I'm also finalizing the implementation of a prominent theme toggle button, defaulting to a dark theme for a modern feel, with plans to add a "clear search" button and handle empty search results gracefully.

**Testing Responsiveness and Themes**

I'm thoroughly examining the layout's adaptability across various viewports, from 1280x800 down to 375px, ensuring seamless transitions. My thoughts are on optimizing column display for smaller screens, whether through vertical stacking or horizontal scrolling. I'm also meticulously testing color palettes for both light and dark themes to guarantee aesthetic appeal and accessibility.

**Finalizing Layout and Interactivity**

I'm confirming the responsive design, ensuring columns stack vertically and cards wrap text without horizontal overflow. I've verified all core requirements, from initial card population and drag-and-drop to search and theming, and am now focusing on the visual details of the color scheme and system font stack.

**Enhancing UI Elements**

I'm currently focused on refining the visual presentation of the Kanban board. My thoughts are on integrating crisp SVG icons for various actions and metadata, and detailing the modal's appearance with smooth animations and clearly defined input fields, including styled radio buttons for priority selection.

**Refining Column and Drop Visuals**

I'm focusing on the visual feedback for columns and drag-and-drop operations. My thoughts are on subtle border highlights when dragging over columns, and the styling of the drop placeholder, including animated height and opacity for a smooth insertion effect. I'm also refining the visual cues for a card being dragged, like reduced opacity and a dashed outline.

**Populating Card Data**

I'm now solidifying the initial data structure for the cards, detailing specific properties like IDs, codes, titles, and priorities. My thoughts are focused on ensuring this initial population accurately reflects realistic task data for the Kanban board.

**Defining Card Properties**

I'm now focused on the precise data attributes for each card. My thoughts are on assigning unique IDs, codes, titles, priorities, tags, and due dates, ensuring a comprehensive and realistic initial dataset for the Kanban board.

**Implementing Drop Logic**

**Finalizing Drop Logic**

I'm completing the drag-and-drop `drop` function. My thoughts are on using the `getDropTarget` algorithm to precisely determine the target column and insertion point, updating the state array accordingly, and then re-rendering the board for a seamless user experience.

**Moving Cards Within Columns**

I'm finalizing the `moveCard` function, which updates the internal state to reflect a card's new position. My thoughts are focused on accurately calculating the `targetIndex` based on the `dropPlaceholder`'s location within the column's children, and then correctly splicing and re-inserting the card into the `cards` array.

**Restructuring Data State**

I'm finalizing the core data structure, opting for a cleaner column-based object. This approach simplifies card movement and state updates significantly, avoiding complex index calculations and making reordering more robust and intuitive. I'm also considering how to integrate theme and search states efficiently within this new structure.

**Simplifying Data Structure**

I've settled on a column-based object for my data. This makes manipulating cards, whether moving, deleting, or adding them, significantly more straightforward and efficient than previous approaches. This restructured state is now the foundation for all future operations.

**Verifying State Operations**

I'm thoroughly testing each core operation against the simplified column-based state structure. Adding, deleting, and moving cards are all proving to be far more intuitive and efficient with this approach. My focus is now on ensuring these operations seamlessly update the UI after each modification.

**Updating State and Filtering**

I'm confirming the logic for moving cards between columns, ensuring precise index calculations and state array updates. My thoughts are now focused on integrating live, case-insensitive search filtering across card titles, tags, and descriptions, and updating column counters to reflect these filtered results dynamically.

**Refining Drop Target Identification**

I'm finalizing how to precisely identify the drop target index. My thoughts are on using the `nextElementSibling` of the drop placeholder to find the ID of the card immediately following it. This ID will then be used to derive the correct insertion index within the column's current state, ensuring accurate card placement after a drag operation.

**Calculating Insertion Index**

I'm finalizing the algorithm for determining the exact insertion point for dropped cards. My thoughts are on leveraging the `nextElementSibling` of the drop placeholder to identify the subsequent card, and then using its index to accurately calculate the `targetIndex` within the column's data structure, ensuring precise reordering.

**Confirming Drop Logic**

I'm meticulously testing the drop logic, especially edge cases like an empty target column or dropping at the end. My thoughts confirm the robustness of the insertion index calculation, ensuring cards land exactly where intended. I'm now refining the visual presentation of the drop placeholder and card elements.

**Designing Card Components**

I'm now detailing the internal layout of each card. My thoughts are on incorporating a header with a code and priority badge on the left, and a delete button on the right, while ensuring the title is prominent. The footer will display tags and either a drag grip or due date. I'm also planning a smooth, animated deletion process and refining the modal for adding new tasks, allowing pre-selection of columns and standardizing form fields like title and description.

**Refining Modal and Search**

I'm now detailing the modal's interactive elements and keyboard shortcuts, focusing on intuitive submission and dismissal. Concurrently, I'm enhancing the header's search bar with visual cues, live filtering, and keyboard shortcuts, including handling empty search results gracefully with a clear prompt.

**Styling Theme Switcher**

I'm refining the theme switcher's design, focusing on its button presentation with relevant icons and text. My thoughts are on implementing smooth transitions for color changes and ensuring high contrast across both dark and light themes. I've decided to default to a dark theme, and will verify WCAG AA compliance for text contrast.

**Finalizing Theme Variables**

I'm completing the CSS variables for both themes, establishing the final color palette and visual properties for backgrounds, borders, and text. My thoughts are on ensuring a cohesive and accessible aesthetic, and refining the shadow and drop zone visuals for both light and dark modes.

**Defining Priority Colors**

I'm specifying the precise colors for priority badges in both themes. My thoughts are on the background, text, and dot colors for high, medium, and low priorities, ensuring clear visual distinction and accessibility across different themes.

**Integrating Theme Switcher**

I'm focusing on the final implementation of the theme switcher. My thoughts are on how to smoothly transition between light and dark modes, ensuring all elements adapt correctly, and verifying the contrast ratios for text elements against both backgrounds for WCAG AA compliance.

**Specifying Priority Colors**

I'm finalizing the exact color definitions for priority indicators across both themes. My thoughts are on the background, text, and dot colors for high, medium, and low priorities, ensuring they are distinct and accessible in both light and dark modes.

**Finalizing UI Elements**

I'm currently refining the visual and interactive components of the Kanban board. My thoughts are on integrating SVG icons for actions and metadata, and polishing the modal with smooth animations and clear input fields, including styled radio buttons for priority selection. I've also settled on a column-based data structure for efficient state management.

**Testing Responsiveness and State**

I'm thoroughly verifying the layout's adaptability across viewports and ensuring all state operations remain in memory. My thoughts are focused on confirming that columns stack vertically on smaller screens and that the modal and search bar scale appropriately without horizontal scrollbars. Drag-and-drop functionality is also under scrutiny.

**Handling Touch and Edge Cases**

I'm confirming that native HTML5 drag and drop, as required for mouse interaction, is robust. My thoughts are now focused on ensuring seamless drag-and-drop behavior, particularly by implementing thorough `dragend` cleanup, adding a document-level `dragend` listener, and preventing drag issues with child elements like delete buttons. I'm also exploring how to set the drag ghost image effectively.

**Cleansing Drag State**

I'm completing the `dragend` cleanup routine, removing the `is-dragging` class and the drop placeholder to restore the UI. My thoughts are now focused on the `dragover` event listener, ensuring the drop placeholder is correctly positioned within the target column, and handling cases where it's dropped at the end of a column.

**Refining Drop Logic**

I'm finalizing the `drop` event handler. My thoughts are focused on how the `moveCard` function correctly uses the calculated `targetIndex` and `targetColumn` to update the internal state, and then how the subsequent `removeDropPlaceholder` cleans up the UI after the card has been moved.

**Calculating Drop Index**

I'm scrutinizing the `targetIndex` calculation when moving cards within the same column. My thoughts are focused on a potential off-by-one error, especially when the card is dropped at a position after its original index, and ensuring the splice and re-insertion logic correctly maintains the card order.

**Ensuring Correct Indexing**

I'm thoroughly verifying the drag-and-drop index calculation logic, simulating various scenarios. My thoughts confirm that when moving a card within the same column, the `targetIndex` correctly adjusts to account for the removed card, ensuring accurate reordering and preventing off-by-one errors.

**Confirming Drop Logic**

**Animating Deletion Sequence**

I'm solidifying the card deletion process. My thoughts now focus on adding a visual fade-out and scale-down animation before the card is removed from the state and DOM, ensuring a smoother user experience. I'm also ensuring the state update and re-render happen only after the animation completes.

**Animating Deletion Sequence**

I'm adding a smooth fade-out and scale-down animation for card deletions, ensuring the state update and DOM removal occur post-animation. My focus is now on refining the modal's form for adding new tasks, including input validation for the title, priority selection, column assignment, and a clear error message display. I'm also ensuring the modal is dismissible via its backdrop, escape key, or close/cancel buttons.

**Displaying Card Information**

I'm now focusing on how column headers and individual cards will be presented. My thoughts involve displaying the status dot, column title, and card count dynamically, especially during searches. For cards, I'm planning to show the task code and a clear priority badge with distinct styling for High, Medium, and Low.

**Designing Card Layout**

I'm finalizing the card's internal structure, incorporating a header with code and priority, a body for the title and description, and a footer for tags and a drag handle. My thoughts also include detailed styling for empty columns and columns with no search matches, along with the clear search button functionality.

**Verifying UI and Interactions**

I'm finalizing keyboard navigation, ensuring Esc closes the modal and shortcut keys focus the search. I'm also testing form submission with Enter and refining button focus states for accessibility. Detailed styling for layered shadows, smooth transitions, and border radii is complete, along with a carefully tuned dark theme.

**Adapting to Mobile Viewports**

I'm currently focusing on ensuring the layout adapts flawlessly to small screens, down to 375px wide, by stacking header elements and allowing vertical scrolling of the entire board. My goal is to eliminate any horizontal scrollbars entirely.

**Testing Layout and Placeholder**

I'm meticulously verifying the layout's responsiveness, ensuring columns stack vertically on smaller screens and fit horizontally on larger ones without scrollbars. I'm also refining the drop placeholder's appearance and animation, aiming for clear visual guidance during drag operations.

**Confirming Visual and Interaction**

I'm validating the visual drop indicator and drag-and-drop event handling. My thoughts confirm that drag initiation from delete buttons is prevented and that priority badge styling is correctly implemented across themes, ensuring a polished and functional interface.

**Defining Priority Colors**

I'm finalizing the exact color definitions for priority indicators across both themes. My thoughts are on the background, text, and dot colors for high, medium, and low priorities, ensuring they are distinct and accessible in both light and dark modes. I'm also designing interactive priority selection buttons for the modal, offering a more user-friendly alternative to a standard dropdown.

**Finalizing Data Structure**

I'm confirming the initial data structure, ensuring it accurately reflects the specified pre-populated cards across the "To do," "In progress," and "Done" columns. My thoughts are focused on verifying that each card has a unique code, title, priority, tag, and date, and that the overall distribution of priorities (2 high, 2 medium, 2 low) is correct.

**Capturing Initial State**

I'm documenting the current state of the Kanban board, noting the synchronous rendering of all six pre-populated cards with their complete details and badges. The header elements, including the search bar, stats, and theme toggle, are also captured, alongside the accurate column counts.

**Testing Search Functionality**

I'm evaluating the live search filtering. My thoughts are on how non-matching cards are hidden and counters update dynamically, with all cards reappearing upon clearing the search.

**Testing Card Addition**

I'm refining the "New Task" modal experience. My thoughts are on its smooth opening animation, automatic focus, and robust validation, including clear error messaging and visual feedback for required fields like the task title.

**Testing Interactions and State**

I'm now focused on verifying the core user interactions: adding tasks via a validated modal, smoothly deleting cards with animations and state updates, and robust drag-and-drop reordering across and within columns. I'm also confirming the theme toggle functions correctly and that the search accurately filters and updates counts.

**Testing Responsive Styling**

I'm thoroughly verifying the responsive styling for smaller viewports, confirming elements like the header and kanban board adapt correctly with appropriate padding and flex wrapping. I'm also ensuring all state remains in memory without relying on browser storage, and that no intrusive alerts or prompts are used.

**Verifying Responsive Layout**

I'm confirming the layout's excellent adaptability across various viewports. From 1280px down to 375px, elements resize and stack correctly, ensuring a native feel without any horizontal scrollbars. I'm also solidifying the visual enhancements like card hover effects and the use of SVG icons.