:root {
      color-scheme: light;
      --paper: oklch(99.5% 0.002 255);
      --paper-soft: oklch(97.8% 0.003 255);
      --ink: oklch(21% 0.018 255);
      --ink-soft: oklch(39% 0.014 255);
      --muted: oklch(54% 0.014 255);
      --line: oklch(90% 0.006 255);
      --line-strong: oklch(78% 0.008 255);
      --accent: oklch(45% 0.105 238);
      --accent-soft: oklch(95% 0.025 238);
      --ease: cubic-bezier(0.22, 1, 0.36, 1);
    }

    * {
      box-sizing: border-box;
    }

    html {
      scroll-behavior: smooth;
      background: var(--paper);
    }

    body {
      min-width: 320px;
      margin: 0;
      overflow-x: hidden;
      color: var(--ink);
      background: var(--paper);
      font-family: "Atkinson Hyperlegible", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      -webkit-font-smoothing: antialiased;
    }

    body::before {
      position: fixed;
      z-index: 0;
      inset: 0;
      content: "";
      pointer-events: none;
      background: linear-gradient(
        90deg,
        var(--paper) 0%,
        var(--paper) 36%,
        oklch(99.5% 0.002 255 / 92%) 45%,
        transparent 64%
      );
    }

    a {
      color: inherit;
    }

    button,
    a {
      -webkit-tap-highlight-color: transparent;
    }

    a:focus-visible,
    button:focus-visible {
      outline: 2px solid var(--accent);
      outline-offset: 4px;
    }

    .site-header {
      position: fixed;
      z-index: 5;
      top: 0;
      right: 0;
      left: 0;
      display: flex;
      align-items: center;
      justify-content: space-between;
      min-height: 64px;
      padding: 0 clamp(20px, 4.5vw, 68px);
      gap: 28px;
      background: oklch(99.5% 0.002 255 / 94%);
      border-bottom: 1px solid var(--line);
    }

    .wordmark {
      display: inline-flex;
      align-items: center;
      gap: 9px;
      font: 650 14px/1 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
      letter-spacing: -0.035em;
      text-decoration: none;
    }

    .wordmark__dot {
      width: 7px;
      height: 7px;
      background: var(--accent);
      border-radius: 50%;
    }

    .site-nav {
      display: flex;
      align-items: center;
      gap: clamp(15px, 2.4vw, 32px);
    }

    .site-nav a {
      color: var(--ink-soft);
      font-size: 12px;
      font-weight: 560;
      text-decoration: none;
    }

    .site-nav a:hover {
      color: var(--ink);
      text-decoration: underline;
      text-decoration-thickness: 1px;
      text-underline-offset: 5px;
    }

    .scene-count {
      min-width: 52px;
      color: var(--muted);
      font: 520 10px/1 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
      text-align: right;
    }

    .scroll-progress {
      position: fixed;
      z-index: 6;
      top: 63px;
      right: 0;
      left: 0;
      height: 1px;
      pointer-events: none;
    }

    .scroll-progress::after {
      display: block;
      width: calc(var(--scroll-progress, 0) * 100%);
      height: 100%;
      content: "";
      background: var(--accent);
      transform-origin: left;
    }

    #diagram {
      position: fixed;
      z-index: 0;
      inset: 0;
      display: block;
      width: 100%;
      height: 100%;
      pointer-events: none;
    }

    main {
      position: relative;
      z-index: 1;
    }

    .chapter {
      display: flex;
      align-items: center;
      min-height: 112vh;
      padding: 15vh clamp(22px, 6.8vw, 104px);
      scroll-margin-top: 64px;
    }

    .chapter:first-child {
      min-height: 126vh;
    }

    .chapter:last-child {
      min-height: 122vh;
    }

    .chapter__inner {
      width: min(540px, 42vw);
      opacity: 0.25;
      transform: translateY(22px);
      transition:
        opacity 500ms var(--ease),
        transform 700ms var(--ease);
    }

    .chapter.is-active .chapter__inner {
      opacity: 1;
      transform: translateY(0);
    }

    h1,
    h2 {
      max-width: 11ch;
      margin: 0;
      font-weight: 720;
      line-height: 0.94;
      letter-spacing: -0.058em;
      text-wrap: balance;
    }

    h1 {
      max-width: 13ch;
      font-size: clamp(52px, 6vw, 84px);
    }

    h2 {
      font-size: clamp(45px, 5.4vw, 78px);
    }

    .chapter__lead {
      max-width: 55ch;
      margin: clamp(25px, 4vh, 42px) 0 0;
      color: var(--ink-soft);
      font-size: clamp(16px, 1.3vw, 19px);
      line-height: 1.58;
    }

    .chapter__body {
      max-width: 62ch;
      margin: 18px 0 0;
      color: var(--muted);
      font-size: 13px;
      line-height: 1.65;
    }

    .facts {
      max-width: 470px;
      padding: 0;
      margin: 30px 0 0;
      list-style: none;
      border-top: 1px solid var(--line);
    }

    .facts li {
      display: grid;
      grid-template-columns: minmax(96px, 0.72fr) 1.5fr;
      align-items: baseline;
      gap: 20px;
      padding: 11px 0;
      border-bottom: 1px solid var(--line);
    }

    .facts span {
      color: var(--muted);
      font: 540 10px/1.3 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    }

    .facts strong {
      font-size: 12px;
      font-weight: 590;
      line-height: 1.4;
    }

    .file-tree,
    .record-example {
      width: min(470px, 100%);
      padding: 17px 18px;
      margin: 28px 0 0;
      overflow-x: auto;
      color: var(--ink-soft);
      background: var(--paper-soft);
      border: 1px solid var(--line);
      border-radius: 4px;
      font: 520 11px/1.55 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
      tab-size: 2;
    }

    .file-tree span,
    .record-example span {
      color: var(--accent);
    }

    .file-tree strong {
      color: var(--ink);
      font-weight: 680;
    }

    .steps {
      max-width: 470px;
      padding: 0;
      margin: 26px 0 0;
      list-style: none;
    }

    .steps li {
      display: grid;
      grid-template-columns: 24px 1fr;
      align-items: baseline;
      gap: 13px;
      padding: 7px 0;
    }

    .steps span {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      width: 20px;
      height: 20px;
      color: var(--accent);
      border: 1px solid oklch(76% 0.055 238);
      border-radius: 50%;
      font: 650 9px/1 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    }

    .steps strong {
      font-size: 12px;
      font-weight: 590;
      line-height: 1.45;
    }

    .chapter__actions {
      display: flex;
      align-items: center;
      gap: 18px;
      margin-top: 30px;
    }

    .button {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      min-height: 38px;
      padding: 0 14px;
      color: var(--accent);
      font-size: 12px;
      font-weight: 650;
      text-decoration: none;
      background: var(--accent-soft);
      border: 1px solid oklch(76% 0.055 238);
      border-radius: 4px;
      transition:
        background-color 180ms var(--ease),
        border-color 180ms var(--ease);
    }

    .button:hover {
      background: oklch(92.5% 0.035 238);
      border-color: var(--accent);
    }

    .text-link {
      color: var(--ink);
      font-size: 12px;
      font-weight: 600;
      text-decoration-thickness: 1px;
      text-underline-offset: 5px;
    }

    .scroll-cue {
      position: absolute;
      bottom: 10vh;
      left: clamp(22px, 6.8vw, 104px);
      display: inline-flex;
      align-items: center;
      gap: 10px;
      color: var(--muted);
      font: 520 10px/1 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
    }

    .scroll-cue::before {
      width: 1px;
      height: 34px;
      content: "";
      background: var(--line-strong);
    }

    .site-footer {
      position: relative;
      z-index: 2;
      display: flex;
      align-items: center;
      justify-content: space-between;
      min-height: 68px;
      padding: 0 clamp(22px, 4.5vw, 68px);
      color: var(--muted);
      font: 520 10px/1.2 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
      background: var(--paper);
      border-top: 1px solid var(--line);
    }

    @media (max-width: 820px) {
      body::before {
        background: linear-gradient(
          180deg,
          transparent 0%,
          transparent 40vh,
          oklch(99.5% 0.002 255 / 88%) 50vh,
          var(--paper) 65vh
        );
      }

      .site-header {
        min-height: 56px;
      }

      .scroll-progress {
        top: 55px;
      }

      .site-nav a:not(:last-child) {
        display: none;
      }

      .chapter {
        align-items: flex-start;
        min-height: 142vh;
        padding-top: 58vh;
        padding-bottom: 16vh;
      }

      .chapter:first-child,
      .chapter:last-child {
        min-height: 148vh;
      }

      .chapter__inner {
        width: 100%;
      }

      h1 {
        font-size: clamp(54px, 15.5vw, 82px);
      }

      h2 {
        font-size: clamp(44px, 12.5vw, 68px);
      }

      .chapter__lead {
        max-width: 42ch;
        font-size: 16px;
      }

      .scroll-cue {
        bottom: 9vh;
      }
    }

    @media (max-width: 480px) {
      .site-nav {
        gap: 12px;
      }

      .site-nav a {
        font-size: 11px;
      }

      .scene-count {
        min-width: auto;
      }

      .chapter {
        padding-right: 22px;
        padding-left: 22px;
      }

      .scroll-cue {
        left: 22px;
      }

      .facts li {
        grid-template-columns: 86px 1fr;
        gap: 14px;
      }

      .file-tree,
      .record-example {
        padding-right: 14px;
        padding-left: 14px;
        font-size: 10px;
      }

      .site-footer span:last-child {
        display: none;
      }
    }

    @media (prefers-reduced-motion: reduce) {
      html {
        scroll-behavior: auto;
      }

      .chapter__inner {
        transform: none;
        transition: none;
      }
    }