Visualization/threejs-learning-playground.html at master · deceive777xv/Visualization · GitHub

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<!doctype html>
<html lang="zh-CN"><head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Three.js 入门实验室</title>
  <style>
    :root {
      --bg:      oklch(98% 0.004 240);
      --surface: oklch(100% 0 0);
      --fg:      oklch(20% 0.02 240);
      --muted:   oklch(50% 0.018 240);
      --border:  oklch(90% 0.006 240);
      --accent:  oklch(56% 0.12 170);

      --accent-soft: color-mix(in oklch, var(--accent) 14%, transparent);
      --fg-soft:     color-mix(in oklch, var(--fg) 6%, transparent);

      --font-display: 'Iowan Old Style', 'Charter', Georgia, 'Times New Roman', serif;
      --font-body:    -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
      --font-mono:    ui-monospace, 'JetBrains Mono', 'SF Mono', Menlo, monospace;

      --fs-h1: clamp(44px, 6vw, 76px);
      --fs-h2: clamp(32px, 4vw, 48px);
      --fs-h3: 22px;
      --fs-lead: 19px;
      --fs-body: 16px;
      --fs-meta: 13px;

      --gap-xs: 8px;
      --gap-sm: 12px;
      --gap-md: 20px;
      --gap-lg: 32px;
      --gap-xl: 56px;
      --gap-2xl: 96px;
      --container: 1180px;
      --gutter: 32px;

      --radius: 10px;
      --radius-lg: 16px;
    }

    *, *::before, *::after { box-sizing: border-box; }
    html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
    body {
      margin: 0;
      background:
        radial-gradient(circle at 12% 10%, color-mix(in oklch, var(--accent) 18%, transparent), transparent 30%),
        radial-gradient(circle at 88% 8%, color-mix(in oklch, oklch(63% 0.16 250) 14%, transparent), transparent 28%),
        radial-gradient(circle at 78% 78%, color-mix(in oklch, oklch(72% 0.14 80) 12%, transparent), transparent 32%),
        linear-gradient(180deg, color-mix(in oklch, var(--bg) 92%, var(--surface)), var(--bg) 48%, color-mix(in oklch, var(--bg) 86%, var(--accent-soft)));
      color: var(--fg);
      font-family: var(--font-body);
      font-size: var(--fs-body);
      line-height: 1.55;
      text-rendering: optimizeLegibility;
      -webkit-font-smoothing: antialiased;
      overflow-x: hidden;
    }
    img, svg, canvas { display: block; max-width: 100%; }
    a { color: inherit; text-decoration: none; }
    button, input, select { font: inherit; }
    button { cursor: pointer; }
    p { text-wrap: pretty; }
    h1, h2, h3, h4 { text-wrap: balance; font-family: var(--font-display); }

    :where(a, button, input, select, [tabindex]):focus-visible {
      outline: 2px solid color-mix(in oklch, var(--accent) 72%, var(--fg));
      outline-offset: 3px;
    }

    @media (prefers-reduced-motion: reduce) {
      html { scroll-behavior: auto; }
      *, *::before, *::after {
        animation-duration: 0.001ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.001ms !important;
      }
    }

    #ambientParticles {
      position: fixed;
      inset: 0;
      z-index: 0;
      width: 100vw;
      height: 100vh;
      pointer-events: none;
      opacity: 0.64;
      mix-blend-mode: multiply;
    }

    #content,
    .pagefoot {
      position: relative;
      z-index: 1;
    }

    .container {
      max-width: var(--container);
      margin-inline: auto;
      padding-inline: var(--gutter);
    }
    .section {
      padding-block: clamp(48px, 8vw, var(--gap-2xl));
    }
    .section + .section { border-top: 1px solid var(--border); }
    .stack { display: flex; flex-direction: column; }
    .stack > * + * { margin-top: var(--gap-md); }
    .row { display: flex; align-items: center; gap: var(--gap-md); }
    .row-between { display: flex; align-items: center; justify-content: space-between; gap: var(--gap-md); }
    .grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--gap-lg); }
    .grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--gap-lg); }
    .grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: var(--gap-md); }
    .grid-2-1 { display: grid; grid-template-columns: 2fr 1fr; gap: var(--gap-xl); align-items: start; }
    .grid-1-2 { display: grid; grid-template-columns: 1fr 2fr; gap: var(--gap-xl); align-items: start; }

    .h1, h1 { font-size: var(--fs-h1); line-height: 1.04; letter-spacing: -0.02em; margin: 0; }
    .h2, h2 { font-size: var(--fs-h2); line-height: 1.1; letter-spacing: -0.015em; margin: 0; }
    .h3, h3 { font-size: var(--fs-h3); font-weight: 600; line-height: 1.3; letter-spacing: -0.005em; margin: 0; }
    .lead { font-size: var(--fs-lead); line-height: 1.55; color: var(--muted); max-width: 60ch; margin: 0; }
    .eyebrow {
      font-family: var(--font-mono);
      font-size: 12px;
      letter-spacing: 0.08em;
      text-transform: uppercase;
      color: var(--accent);
      margin: 0 0 var(--gap-md);
    }
    .meta { font-family: var(--font-mono); font-size: var(--fs-meta); color: var(--muted); }
    .num { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }

    .topnav {
      position: sticky;
      top: 0;
      z-index: 10;
      background: color-mix(in oklch, var(--bg) 92%, transparent);
      backdrop-filter: blur(12px);
      border-bottom: 1px solid var(--border);
    }
    .topnav-inner {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding-block: 14px;
      gap: var(--gap-md);
    }
    .topnav .logo {
      font-family: var(--font-display);
      font-size: 19px;
      font-weight: 600;
      letter-spacing: -0.01em;
      white-space: nowrap;
    }
    .topnav nav { display: flex; gap: var(--gap-lg); }
    .topnav nav a { font-size: 14px; color: var(--muted); }
    .topnav nav a:hover { color: var(--fg); }
    .topnav-actions {
      display: flex;
      align-items: center;
      gap: var(--gap-sm);
    }

    .motion-toggle {
      min-height: 40px;
      padding: 9px 12px;
      border: 1px solid var(--border);
      border-radius: var(--radius);
      background: color-mix(in oklch, var(--surface) 74%, transparent);
      color: var(--muted);
      font-size: 13px;
    }
    .motion-toggle:hover,
    .motion-toggle[aria-pressed="true"] {
      color: var(--fg);
      border-color: color-mix(in oklch, var(--fg) 28%, var(--border));
      background: var(--surface);
    }
    .motion-toggle[disabled] {
      cursor: default;
      opacity: 0.62;
    }

    .pagefoot {
      padding-block: var(--gap-xl);
      color: var(--muted);
      font-size: 13px;
      border-top: 1px solid var(--border);
    }
    .pagefoot .row-between { flex-wrap: wrap; gap: var(--gap-md); }

    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      gap: 8px;
      padding: 11px 20px;
      border-radius: var(--radius);
      border: 1px solid transparent;
      font-size: 15px;
      font-weight: 500;
      letter-spacing: -0.005em;
      transition: transform 0.05s ease, background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
      min-height: 44px;
    }
    .btn:active { transform: translateY(1px); }
    .btn-primary { background: var(--accent); color: var(--surface); border-color: var(--accent); }
    .btn-primary:hover { background: color-mix(in oklch, var(--accent) 88%, black); }
    .btn-secondary { background: transparent; color: var(--fg); border-color: var(--border); }
    .btn-secondary:hover { border-color: var(--fg); }
    .btn-ghost { background: transparent; color: var(--fg); border-color: transparent; padding-inline: 8px; }
    .btn-ghost:hover { color: var(--fg); background: var(--fg-soft); }
    .btn-arrow::after { content: '→'; transition: transform 0.15s ease; }
    .btn-arrow:hover::after { transform: translateX(2px); }

    .card {
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius-lg);
      padding: 28px;
    }
    .card-flat { background: transparent; border: 0; padding: 0; }
    .feature .feature-mark {
      width: 36px;
      height: 36px;
      display: grid;
      place-items: center;
      border: 1px solid var(--border);
      border-radius: 10px;
      color: var(--fg);
      margin-bottom: var(--gap-md);
      background: var(--surface);
    }
    .feature .feature-mark svg { width: 18px; height: 18px; }
    .feature h3 { margin-bottom: 6px; }
    .feature p { margin: 0; color: var(--muted); font-size: 15px; }

    .pill {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      padding: 4px 10px;
      background: var(--fg-soft);
      color: var(--fg);
      border-radius: 999px;
      font-family: var(--font-mono);
      font-size: 11px;
      letter-spacing: 0.04em;
      text-transform: uppercase;
    }
    .tag {
      display: inline-flex;
      align-items: center;
      padding: 4px 10px;
      background: transparent;
      color: var(--muted);
      border: 1px solid var(--border);
      border-radius: 999px;
      font-size: 12px;
    }

    .input, .select {
      width: 100%;
      padding: 11px 14px;
      border: 1px solid var(--border);
      border-radius: var(--radius);
      background: var(--surface);
      color: var(--fg);
      font: inherit;
      font-size: 15px;
      min-height: 44px;
    }
    .input:focus, .select:focus {
      outline: 2px solid var(--accent-soft);
      border-color: var(--accent);
    }

    .rule { border: 0; border-top: 1px solid var(--border); margin: 0; }
    .hero { padding-block: clamp(72px, 10vw, 136px); }
    .hero h1 { margin-bottom: var(--gap-md); }
    .hero .lead { margin-bottom: var(--gap-lg); }
    .hero-cta { display: inline-flex; gap: var(--gap-sm); flex-wrap: wrap; }
    .hero-split {
      display: grid;
      grid-template-columns: minmax(0, 0.9fr) minmax(360px, 1.1fr);
      gap: var(--gap-2xl);
      align-items: center;
    }

    .lab-preview {
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: 24px;
      padding: 18px;
      box-shadow: 0 24px 60px color-mix(in oklch, var(--fg) 10%, transparent);
    }
    .preview-top {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 4px 4px 14px;
      gap: var(--gap-sm);
      color: var(--muted);
    }
    .preview-dots { display: flex; gap: 6px; }
    .preview-dots span {
      width: 9px;
      height: 9px;
      border-radius: 999px;
      background: var(--border);
    }
    .preview-stage {
      position: relative;
      min-height: 360px;
      border-radius: 18px;
      overflow: hidden;
      background:
        radial-gradient(circle at 74% 24%, color-mix(in oklch, var(--accent) 24%, transparent), transparent 28%),
        radial-gradient(circle at 24% 18%, color-mix(in oklch, oklch(64% 0.16 245) 18%, transparent), transparent 32%),
        linear-gradient(135deg, color-mix(in oklch, var(--surface) 82%, var(--accent-soft)), transparent 52%),
        linear-gradient(90deg, var(--fg-soft) 1px, transparent 1px),
        linear-gradient(0deg, var(--fg-soft) 1px, transparent 1px),
        color-mix(in oklch, var(--bg) 78%, var(--surface));
      background-size: auto, auto, auto, 34px 34px, 34px 34px, auto;
      background-repeat: no-repeat, no-repeat, no-repeat, repeat, repeat, no-repeat;
      display: grid;
      place-items: center;
    }
    .preview-stage::before,
    .preview-stage::after {
      content: '';
      position: absolute;
      inset: 10%;
      border: 1px solid color-mix(in oklch, var(--accent) 34%, transparent);
      border-radius: 50%;
      transform: rotate(-18deg) scaleY(0.42);
      display: none;
      pointer-events: none;
    }
    .preview-stage::after {
      inset: 22% 14%;
      border-color: color-mix(in oklch, var(--fg) 14%, transparent);
      transform: rotate(20deg) scaleY(0.36);
    }
    .preview-stage canvas {
      position: relative;
      z-index: 1;
      width: 100%;
      height: 360px;
    }

    .learning-shell {
      display: grid;
      grid-template-columns: 1fr;
      gap: var(--gap-md);
      align-items: stretch;
    }
    .lesson-picker {
      padding: 0;
      border: 0;
      background: transparent;
      box-shadow: none;
    }
    .lesson-picker-head {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: var(--gap-md);
    }
    .lesson-picker-head .meta { margin: 0; }
    .lesson-menu {
      position: relative;
      display: block;
      align-items: center;
      isolation: isolate;
      border: 0;
      border-radius: 18px;
      background: transparent;
      overflow: hidden;
    }
    .lesson-options {
      position: relative;
      display: block;
      --lesson-index: 1;
      min-width: 0;
      height: 88px;
      overflow-x: hidden;
      overflow-y: hidden;
      scrollbar-width: none;
      padding: 0;
      border: 0;
      border-radius: 18px;
      background: transparent;
    }
    .lesson-options::-webkit-scrollbar { display: none; }
    .lesson-options:focus-visible {
      outline: 2px solid color-mix(in oklch, var(--accent) 62%, var(--fg));
      outline-offset: 4px;
    }
    .lesson-tab {
      position: absolute;
      inset: 0;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      width: 100%;
      min-width: 0;
      text-align: center;
      border: 1px solid var(--border);
      background: var(--surface);
      color: var(--fg);
      border-radius: 18px;
      padding: 14px 58px;
      min-height: 0;
      opacity: 0;
      pointer-events: none;
      transform: translateX(calc(var(--lesson-offset, 0) * 110%));
      transition: transform 0.26s ease, opacity 0.16s ease;
    }
    .lesson-tab:hover,
    .lesson-tab:active,
    .lesson-tab[aria-current="true"] {
      background: var(--surface);
      opacity: 1;
      pointer-events: auto;
    }
    .lesson-tab:focus-visible {
      outline: 2px solid color-mix(in oklch, var(--accent) 62%, var(--fg));
      outline-offset: -6px;
    }
    .lesson-tab strong {
      display: block;
      font-family: var(--font-display);
      font-size: 15px;
      line-height: 1.2;
      margin-bottom: 2px;
    }
    .lesson-tab span {
      display: block;
      color: var(--muted);
      font-size: 13px;
    }
    .lesson-nav {
      position: absolute;
      top: 50%;
      z-index: 2;
      width: 42px;
      height: 42px;
      display: grid;
      place-items: center;
      border: 0;
      border-radius: 0;
      background: transparent;
      color: var(--muted);
      transition: opacity 0.15s ease, color 0.15s ease;
      font-family: var(--font-body);
      font-size: 0;
      line-height: 1;
      transform: translateY(-50%);
    }
    .lesson-nav.prev {
      left: 8px;
      border-radius: 12px;
    }
    .lesson-nav.next {
      right: 8px;
      border-radius: 12px;
    }
    .lesson-nav::before {
      content: "";
      width: 13px;
      height: 13px;
      border-top: 4px solid currentColor;
      border-left: 4px solid currentColor;
      transform-origin: center;
    }
    .lesson-nav.prev::before { transform: rotate(-45deg); }
    .lesson-nav.next::before { transform: rotate(135deg); }
    .lesson-nav:hover { background: transparent; color: var(--fg); }
    .lesson-nav:focus-visible {
      outline: 2px solid color-mix(in oklch, var(--accent) 62%, var(--fg));
      outline-offset: 0;
    }
    .lesson-nav[disabled] {
      opacity: 0.36;
      pointer-events: none;
    }

    .workbench {
      --workbench-height: clamp(700px, 72vh, 780px);
      display: grid;
      grid-template-columns: minmax(420px, 1fr) minmax(360px, 0.9fr);
      gap: var(--gap-md);
      align-items: stretch;
    }
    .workbench > .tool-panel,
    .workbench > .code-window {
      height: var(--workbench-height);
      min-height: 0;
    }
    .tool-panel {
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius-lg);
      padding: 20px;
      display: grid;
      grid-template-rows: auto auto auto minmax(220px, 1fr) auto;
      overflow: hidden;
    }
    .tool-panel h3 { margin-bottom: 8px; }
    .tool-panel p { color: var(--muted); margin: 0; font-size: 14px; }
    .lesson-insights {
      display: grid;
      grid-template-columns: repeat(3, minmax(0, 1fr));
      gap: 8px;
      margin-top: 14px;
    }
    .lesson-insights span {
      border: 1px solid var(--border);
      border-radius: 14px;
      padding: 10px;
      background: color-mix(in oklch, var(--bg) 62%, var(--surface));
      min-width: 0;
    }
    .lesson-insights b,
    .lesson-insights em {
      display: block;
      font-style: normal;
    }
    .lesson-insights b {
      font-size: 11px;
      color: var(--muted);
      font-family: var(--font-mono);
      text-transform: uppercase;
      letter-spacing: 0.04em;
      margin-bottom: 4px;
    }
    .lesson-insights em {
      font-size: 13px;
      line-height: 1.35;
      color: var(--fg);
    }
    .scene-canvas-wrap {
      position: relative;
      margin-top: 14px;
      border: 1px solid var(--border);
      border-radius: 18px;
      overflow: hidden;
      min-height: 220px;
      background:
        linear-gradient(90deg, var(--fg-soft) 1px, transparent 1px),
        linear-gradient(0deg, var(--fg-soft) 1px, transparent 1px),
        color-mix(in oklch, var(--bg) 84%, var(--surface));
      background-size: 28px 28px;
    }
    .scene-status {
      position: absolute;
      left: 14px;
      bottom: 12px;
      z-index: 2;
      max-width: calc(100% - 28px);
      padding: 6px 10px;
      border: 1px solid color-mix(in oklch, var(--fg) 12%, transparent);
      border-radius: 10px;
      background: color-mix(in oklch, var(--surface) 84%, transparent);
      color: var(--muted);
      font-size: 12px;
      backdrop-filter: blur(10px);
      transition: opacity 0.18s ease, transform 0.18s ease;
    }
    .scene-canvas-wrap.is-ready .scene-status {
      opacity: 0;
      transform: translateY(4px);
      pointer-events: none;
    }
    .scene-canvas-wrap.is-error .scene-status {
      color: var(--fg);
      border-color: color-mix(in oklch, var(--fg) 22%, var(--border));
      opacity: 1;
      transform: none;
    }
    .scene-canvas-wrap canvas {
      display: block;
      width: 100%;
      height: 100%;
      min-height: 0;
    }
    .controls {
      display: grid;
      gap: 12px;
      margin-top: 14px;
      padding-top: 14px;
    }
    .controls .grid-2 { gap: 10px; }
    .control-group { display: grid; gap: 8px; }
    .control-label {
      font-size: 12px;
      color: var(--muted);
      font-family: var(--font-mono);
      letter-spacing: 0.04em;
      text-transform: uppercase;
    }
    .segmented {
      display: flex;
      gap: 8px;
      flex-wrap: wrap;
    }
    .shape-btn {
      border: 1px solid var(--border);
      background: var(--surface);
      color: var(--fg);
      border-radius: 999px;
      padding: 8px 12px;
      min-height: 40px;
    }
    .shape-btn:hover { border-color: var(--fg); }
    .shape-btn.active {
      border-color: var(--accent);
      background: var(--accent-soft);
    }
    .toggle-row {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: var(--gap-md);
      border-top: 1px solid var(--border);
      padding-top: 14px;
    }
    .toggle-row input { accent-color: var(--accent); width: 18px; height: 18px; }
    .range-row {
      display: grid;
      grid-template-columns: 1fr auto;
      gap: var(--gap-sm);
      align-items: center;
    }
    .range-row input { accent-color: var(--accent); width: 100%; }

    .code-window {
      background: color-mix(in oklch, var(--fg) 94%, var(--surface));
      color: var(--surface);
      border: 1px solid color-mix(in oklch, var(--fg) 74%, var(--surface));
      border-radius: var(--radius-lg);
      overflow: hidden;
      display: flex;
      flex-direction: column;
    }
    .code-head {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: var(--gap-sm);
      padding: 14px 16px;
      border-bottom: 1px solid color-mix(in oklch, var(--surface) 16%, transparent);
    }
    .code-head span {
      font-family: var(--font-mono);
      font-size: 12px;
      color: color-mix(in oklch, var(--surface) 72%, transparent);
    }
    .copy-btn {
      border: 1px solid color-mix(in oklch, var(--surface) 20%, transparent);
      background: transparent;
      color: var(--surface);
      border-radius: 9px;
      padding: 8px 10px;
      min-height: 38px;
    }
    .copy-btn:hover { background: color-mix(in oklch, var(--surface) 9%, transparent); }
    .copy-btn[disabled] {
      cursor: wait;
      opacity: 0.72;
    }
    .code-window pre {
      margin: 0;
      padding: 18px;
      overflow: auto;
      overscroll-behavior: contain;
      scrollbar-gutter: stable;
      font-family: var(--font-mono);
      font-size: 13px;
      line-height: 1.55;
      white-space: pre;
      min-height: 0;
      flex: 1 1 auto;
    }
    .code-window code {
      display: block;
      min-width: max-content;
    }
    .lesson-note {
      display: grid;
      gap: 10px;
      margin-top: 14px;
      color: var(--muted);
      font-size: 14px;
    }
    .lesson-note a {
      border-bottom: 1px solid var(--border);
    }
    .lesson-note a:hover { color: var(--fg); border-color: var(--fg); }

    .path-list {
      display: grid;
      gap: 0;
    }
    .path-row {
      display: grid;
      grid-template-columns: 120px 1fr 110px;
      gap: var(--gap-lg);
      padding: 22px 0;
      border-top: 1px solid var(--border);
      align-items: baseline;
    }
    .path-row h3 { font-size: 19px; }
    .path-row p { margin: 4px 0 0; color: var(--muted); font-size: 14px; }
    .path-row .pull { text-align: right; }

    .docs-grid {
      display: grid;
      grid-template-columns: repeat(4, minmax(0, 1fr));
      gap: var(--gap-md);
    }
    .doc-card {
      min-height: 154px;
      display: flex;
      flex-direction: column;
      justify-content: space-between;
      background: var(--surface);
      border: 1px solid var(--border);
      border-radius: var(--radius-lg);
      padding: 18px;
      transition: border-color 0.15s ease, transform 0.05s ease;
    }
    .doc-card:hover {
      border-color: var(--accent);
      transform: translateY(-1px);
    }
    .doc-card strong {
      font-family: var(--font-display);
      font-size: 18px;
      line-height: 1.2;
    }
    .doc-card span {
      color: var(--muted);
      font-size: 13px;
      margin-top: 8px;
    }
    .doc-card small {
      margin-top: 18px;
      font-family: var(--font-mono);
      color: var(--muted);
    }

    .cta-strip {
      text-align: center;
    }
    .cta-strip .container { max-width: 680px; }
    .cta-strip .lead { margin: 16px auto 32px; }

    @media (max-width: 1080px) {
      .hero-split,
      .learning-shell {
        grid-template-columns: 1fr;
      }
      .docs-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
      .preview-stage, .preview-stage canvas { min-height: 300px; height: 300px; }
    }
    @media (max-width: 980px) {
      .workbench { --workbench-height: auto; }
      .workbench,
      .lesson-insights {
        grid-template-columns: 1fr;
      }
      .workbench > .tool-panel {
        height: auto;
      }
      .workbench > .code-window {
        height: min(560px, 70vh);
        min-height: 420px;
      }
      .scene-canvas-wrap {
        flex: none;
        min-height: 0;
      }
      .scene-canvas-wrap canvas {
        height: 300px;
        min-height: 300px;
      }
    }
    @media (max-width: 920px) {
      .grid-2, .grid-3, .grid-4, .grid-2-1, .grid-1-2 { grid-template-columns: 1fr; }
      .topnav nav { display: none; }
      .topnav-inner { align-items: flex-start; }
      .topnav-actions { display: none; }
      .path-row {
        grid-template-columns: 1fr;
        gap: 8px;
      }
      .path-row .pull { text-align: left; }
    }
    @media (max-width: 620px) {
      :root { --gutter: 20px; }
      .hero-cta, .segmented { width: 100%; }
      .hero-cta .btn, .segmented button { flex: 1 1 auto; }
      .docs-grid { grid-template-columns: 1fr; }
      .code-window {
        height: min(500px, 68vh);
        min-height: 360px;
      }
      .code-window pre { font-size: 12px; }
      .lesson-picker-head {
        align-items: flex-start;
      }
      .lesson-options {
        min-width: 0;
        height: 88px;
        padding: 0;
      }
      .lesson-tab {
        padding: 12px 48px;
        min-height: 0;
      }
      .lesson-nav {
        width: 40px;
        height: 40px;
      }
      .scene-canvas-wrap canvas {
        height: 260px;
        min-height: 260px;
      }
    }
  </style>
</head>
<body>
  <canvas id="ambientParticles" aria-hidden="true"></canvas>
  <header class="topnav" data-od-id="topnav">
    <div class="container topnav-inner">
      <a class="logo" href="#intro">Three.js 入门实验室</a>
      <nav aria-label="主导航">
        <a href="#concepts">概念</a>
        <a href="#playground">练习场</a>
        <a href="#roadmap">路线</a>
        <a href="#docs">官方文档</a>
      </nav>
      <div class="topnav-actions">
        <button class="motion-toggle" id="motionToggle" type="button" aria-pressed="false">暂停粒子</button>
        <a class="btn btn-secondary" href="#playground">进入练习场</a>
      </div>
    </div>
  </header>

  <main id="content">
    <section class="section hero" id="intro" data-od-id="hero-split">
      <div class="container hero-split">
        <div>
          <p class="eyebrow">BEGINNER · PLAYGROUND</p>
          <h1>从第一个立方体开始学 Three.js</h1>
          <p class="lead">学习场景、相机、渲染器、材质、光照和动画。</p>
          <div class="hero-cta" style="margin-top: 28px;">
            <a class="btn btn-primary" href="#playground">打开交互练习</a>
            <a class="btn btn-ghost btn-arrow" href="https://threejs.org/manual/#zh/fundamentals" target="_blank" rel="noreferrer">查看官方手册</a>
          </div>
        </div>
        <div class="lab-preview" aria-label="Three.js 学习画布预览">
          <div class="preview-top">
            <div class="preview-dots" aria-hidden="true"><span></span><span></span><span></span></div>
            <span class="meta">rotating cube / particles</span>
          </div>
          <div class="preview-stage">
            <canvas id="heroCanvas" aria-label="旋转立方体与粒子效果预览画布"></canvas>
          </div>
        </div>
      </div>
    </section>

    <section class="section" id="concepts" data-od-id="features">
      <div class="container stack" style="gap: 56px;">
        <div style="max-width: 38ch;">
          <p class="eyebrow">LEARNING MODEL</p>
          <h2>建立三维直觉</h2>
        </div>
        <div class="grid-3">
          <div class="feature card-flat">

            <h3>概念术语</h3>
            <p>每个术语都配一个可调预览：你改几何体、材质和阴影，旁边的代码同步变化。</p>
          </div>
          <div class="feature card-flat">

            <h3>代码示例</h3>
            <p>从创建 Scene 到 animate 循环按顺序展开，适合第一次接触 WebGL 的学习者复制试跑。</p>
          </div>
          <div class="feature card-flat">

            <h3>官方文档</h3>
            <p>课程卡片直接链接到 threejs.org 的 Scene、Camera、Renderer、GLTFLoader 等文档页。</p>
          </div>
        </div>
      </div>
    </section>

    <section class="section" id="playground" data-od-id="playground">
      <div class="container stack" style="gap: 32px;">
        <div class="row-between" style="align-items: end;">
          <div style="max-width: 46ch;">
            <p class="eyebrow">LIVE WORKBENCH</p>
            <h2>调参数+读代码</h2>
          </div>
          <span class="pill" id="statusPill" role="status" aria-live="polite">预览已就绪</span>
        </div>

        <div class="learning-shell">
          <aside class="card lesson-picker" aria-label="课程主题">

            <div class="lesson-menu" aria-label="课程模块滑动选择">
              <button class="lesson-nav prev" id="lessonPrev" type="button" aria-label="上一个模块">&lt;</button>
              <div class="lesson-options" id="lessonOptions" aria-label="Three.js 入门课程" aria-live="polite">
                <button class="lesson-tab" id="lesson-tab-concepts" aria-current="false" data-lesson="concepts" type="button" tabindex="-1">
                  <strong>基础概念</strong>
                  <span>Object3D、Mesh、Geometry 的关系</span>
                </button>
                <button class="lesson-tab" id="lesson-tab-scene" aria-current="true" data-lesson="scene" type="button">
                  <strong>场景 / 相机 / 渲染器</strong>
                  <span>把三维世界显示到网页上</span>
                </button>
                <button class="lesson-tab" id="lesson-tab-material" aria-current="false" data-lesson="material" type="button" tabindex="-1">
                  <strong>材质 / 光照 / 阴影</strong>
                  <span>让物体有质感和空间方向</span>
                </button>
                <button class="lesson-tab" id="lesson-tab-model" aria-current="false" data-lesson="model" type="button" tabindex="-1">
                  <strong>模型加载</strong>
                  <span>用 GLTFLoader 引入外部模型</span>
                </button>
                <button class="lesson-tab" id="lesson-tab-motion" aria-current="false" data-lesson="motion" type="button" tabindex="-1">
                  <strong>动画与交互</strong>
                  <span>requestAnimationFrame 与 Raycaster</span>
                </button>
              </div>
              <button class="lesson-nav next" id="lessonNext" type="button" aria-label="下一个模块">&gt;</button>
            </div>
          </aside>

          <div class="workbench">
            <section class="tool-panel" aria-label="实时预览面板" data-od-id="workbench-preview">
              <h3 id="lessonTitle">场景 / 相机 / 渲染器</h3>
              <p id="lessonSummary">Scene 放物体，PerspectiveCamera 决定观察方式，WebGLRenderer 把结果绘制到 canvas。</p>
              <div class="lesson-insights" aria-label="当前模块学习提示">
                <span>
                  <b>核心</b>
                  <em id="lessonCore">Scene / Camera / Renderer 的分工</em>
                </span>
                <span>
                  <b>练习</b>
                  <em id="lessonPractice">调整视角与视锥体，观察画面变化</em>
                </span>
                <span>
                  <b>易错点</b>
                  <em id="lessonPitfall">窗口变化后要同步更新相机比例</em>
                </span>
              </div>

              <div class="scene-canvas-wrap">
                <canvas id="sceneCanvas" aria-label="交互式三维预览"></canvas>
                <span class="scene-status" id="sceneStatus" role="status" aria-live="polite">实时场景加载中…</span>
              </div>

              <div class="controls">
                <div class="control-group">
                  <span class="control-label">几何体</span>
                  <div class="segmented" aria-label="选择几何体">
                    <button class="shape-btn active" data-shape="box" aria-pressed="true">立方体</button>
                    <button class="shape-btn" data-shape="sphere" aria-pressed="false">球体</button>
                    <button class="shape-btn" data-shape="torus" aria-pressed="false">圆环</button>
                  </div>
                </div>

                <div class="grid-2">
                  <label class="control-group">
                    <span class="control-label">材质</span>
                    <select class="select" id="materialSelect">
                      <option value="standard">MeshStandardMaterial</option>
                      <option value="basic">MeshBasicMaterial</option>
                      <option value="wireframe">线框材质</option>
                    </select>
                  </label>
                  <label class="control-group">
                    <span class="control-label">动画速度</span>
                    <span class="range-row">
                      <input id="speedRange" type="range" min="0" max="2" step="0.25" value="1">
                      <span class="meta num" id="speedValue">1.00</span>
                    </span>
                  </label>
                </div>

                <label class="toggle-row">
                  <span>
                    <strong style="display:block;">开启阴影</strong>
                    <span class="meta">配合 DirectionalLight 观察体积感</span>
                  </span>
                  <input id="shadowToggle" type="checkbox" checked="">
                </label>