/* ==========================================================================
   Know Your Unknowns — styles.css
   ========================================================================== */

/* ---------- Reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
html, body, h1, h2, h3, h4, p, ul, ol, li, figure, blockquote, dl, dd {
  margin: 0;
}
ul, ol { padding: 0; list-style: none; }
img, svg { display: block; max-width: 100%; }
button, input, textarea { font: inherit; color: inherit; }
button { cursor: pointer; background: none; border: none; }
a { color: inherit; text-decoration: none; }
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ---------- Design tokens ---------- */
:root {
  /* light theme (default) */
  --bg: #fafafa;
  --surface: #ffffff;
  --surface-2: #f2f2f4;
  --border: #e2e2e6;
  --text: #1a1a1a;
  --text-muted: #5c5c66;
  --accent: #0d9488;
  --accent-text: #0a6e64;   /* for body/link text — meets 4.5:1 */
  --accent-strong: #0a6e64; /* solid button bg w/ white label */
  --on-accent: #ffffff;

  /* quadrant semantic colors */
  --q-known-known: #375074;
  --q-known-unknown: #8a5a00;
  --q-unknown-known: #7c3aed;
  --q-unknown-unknown: #c62828;

  /* stage semantic colors */
  --s-pre: #137333;
  --s-during: #1656c9;
  --s-post: #5b21b6;

  --radius: 12px;
  --space-1: 8px;
  --space-2: 16px;
  --space-3: 24px;
  --space-4: 32px;
  --space-5: 48px;
  --space-6: 64px;
  --section-pad: 96px;
  --shadow: 0 8px 24px rgba(20, 20, 30, 0.08);
  --nav-h: 64px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Noto Sans TC", "PingFang TC", "Microsoft JhengHei", sans-serif;
  --font-mono: "SF Mono", "JetBrains Mono", "Menlo", "Consolas", monospace;
  --transition-fast: 180ms ease;
  --transition-med: 400ms ease-out;
}

[data-theme="dark"] {
  --bg: #0d1117;
  --surface: #161b22;
  --surface-2: #1c2129;
  --border: #30363d;
  --text: #e6edf3;
  --text-muted: #8b949e;
  --accent: #2dd4bf;
  --accent-text: #2dd4bf;
  --accent-strong: #2dd4bf;
  --on-accent: #04201d;

  --q-known-known: #93a8c7;
  --q-known-unknown: #f2c14e;
  --q-unknown-known: #cf9dfa;
  --q-unknown-unknown: #ff8a80;

  --s-pre: #5ee69c;
  --s-during: #79b8ff;
  --s-post: #b79cf7;

  --shadow: none;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0d1117;
    --surface: #161b22;
    --surface-2: #1c2129;
    --border: #30363d;
    --text: #e6edf3;
    --text-muted: #8b949e;
    --accent: #2dd4bf;
    --accent-text: #2dd4bf;
    --accent-strong: #2dd4bf;
    --on-accent: #04201d;

    --q-known-known: #93a8c7;
    --q-known-unknown: #f2c14e;
    --q-unknown-known: #cf9dfa;
    --q-unknown-unknown: #ff8a80;

    --s-pre: #5ee69c;
    --s-during: #79b8ff;
    --s-post: #b79cf7;

    --shadow: none;
  }
}

@media (max-width: 639px) {
  :root { --section-pad: 56px; }
}

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

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  transition: background var(--transition-fast), color var(--transition-fast);
}

.container {
  max-width: 1120px;
  margin: 0 auto;
  padding-left: var(--space-3);
  padding-right: var(--space-3);
}

section {
  scroll-margin-top: var(--nav-h);
  padding-top: var(--section-pad);
  padding-bottom: var(--section-pad);
}

h1, h2, h3, h4 { font-weight: 700; line-height: 1.3; }
h2 { font-size: clamp(1.5rem, 1.1rem + 1.6vw, 2.25rem); margin-bottom: var(--space-3); }
h3 { font-size: 1.25rem; margin-bottom: var(--space-2); }
h4 { font-size: 1rem; margin-bottom: var(--space-1); }
p { margin-bottom: var(--space-2); color: var(--text); }
.lead { font-size: 1.1rem; color: var(--text-muted); max-width: 72ch; }
.text-muted { color: var(--text-muted); }
.small { font-size: 0.85rem; }

strong { font-weight: 700; }
code {
  font-family: var(--font-mono);
  background: var(--surface-2);
  padding: 0.1em 0.4em;
  border-radius: 4px;
  font-size: 0.9em;
}
blockquote {
  border-left: 3px solid var(--accent);
  padding-left: var(--space-2);
  color: var(--text-muted);
  font-style: italic;
  margin: var(--space-2) 0;
}

.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  left: 8px;
  top: -48px;
  background: var(--accent);
  color: var(--on-accent);
  padding: 10px 16px;
  border-radius: 8px;
  z-index: 1000;
  transition: top var(--transition-fast);
}
.skip-link:focus {
  top: 8px;
}

/* Reveal-on-scroll */
.reveal {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity var(--transition-med), transform var(--transition-med);
}
.reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 22px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 0.95rem;
  border: 1px solid transparent;
  transition: transform var(--transition-fast), background var(--transition-fast), border-color var(--transition-fast);
}
.btn:hover { transform: translateY(-1px); }
.btn-primary {
  background: var(--accent-strong);
  color: var(--on-accent);
}
.btn-secondary {
  background: transparent;
  color: var(--text);
  border-color: var(--border);
}
.btn-secondary:hover { border-color: var(--accent); }
.btn-disabled {
  background: var(--surface-2);
  color: var(--text-muted);
  border-color: var(--border);
  cursor: not-allowed;
}
.btn-disabled:hover { transform: none; }
.btn-disabled .soon-tag {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 999px;
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text-muted);
}

/* ---------- Top nav ---------- */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 500;
  height: var(--nav-h);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.site-nav .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}
.nav-brand {
  font-weight: 700;
  font-size: 1.05rem;
  white-space: nowrap;
}
.nav-links {
  display: flex;
  gap: var(--space-3);
  align-items: center;
}
.nav-links a {
  font-size: 0.92rem;
  color: var(--text-muted);
  padding: 8px 2px;
  border-bottom: 2px solid transparent;
  transition: color var(--transition-fast), border-color var(--transition-fast);
}
.nav-links a:hover,
.nav-links a.is-active {
  color: var(--text);
  border-color: var(--accent);
}
.nav-right { display: flex; align-items: center; gap: var(--space-2); }
.nav-toggle { display: none; font-size: 1.4rem; }
.theme-toggle {
  width: 40px; height: 40px;
  display: inline-flex; align-items: center; justify-content: center;
  border: 1px solid var(--border);
  border-radius: 50%;
  font-size: 1.1rem;
}
.theme-toggle:hover { border-color: var(--accent); }

/* ---------- Progress rail (desktop) ---------- */
.progress-rail {
  position: fixed;
  right: 24px;
  top: 50%;
  transform: translateY(-50%);
  z-index: 400;
  display: flex;
  flex-direction: column;
  gap: 14px;
  padding: 14px 10px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 999px;
  box-shadow: var(--shadow);
}
.progress-rail button {
  width: 12px; height: 12px;
  border-radius: 50%;
  background: var(--border);
  transition: background var(--transition-fast), transform var(--transition-fast);
}
.progress-rail button[data-stage="pre"].is-current { background: var(--s-pre); transform: scale(1.4); }
.progress-rail button[data-stage="during"].is-current { background: var(--s-during); transform: scale(1.4); }
.progress-rail button[data-stage="post"].is-current { background: var(--s-post); transform: scale(1.4); }

/* ---------- Back to top ---------- */
.back-to-top {
  position: fixed;
  right: 24px;
  bottom: 24px;
  z-index: 400;
  width: 44px; height: 44px;
  border-radius: 50%;
  background: var(--accent-strong);
  color: var(--on-accent);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.2rem;
  box-shadow: var(--shadow);
  opacity: 0;
  pointer-events: none;
  transform: translateY(8px);
  transition: opacity var(--transition-fast), transform var(--transition-fast);
}
.back-to-top.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

/* ==========================================================================
   S0 — Hero
   ========================================================================== */
.hero {
  min-height: calc(100vh - var(--nav-h));
  display: flex;
  flex-direction: column;
  justify-content: center;
  position: relative;
  overflow: hidden;
}
.hero-illustration {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: stretch;
  gap: 0;
  height: 220px;
  margin-bottom: var(--space-5);
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
}
.hero-map {
  background-image:
    linear-gradient(var(--border) 1px, transparent 1px),
    linear-gradient(90deg, var(--border) 1px, transparent 1px);
  background-size: 24px 24px;
  background-color: var(--surface);
}
.hero-territory {
  background: var(--surface);
  position: relative;
}
.hero-territory::before {
  content: "";
  position: absolute;
  inset: 18px;
  background: color-mix(in srgb, var(--accent) 22%, transparent);
  clip-path: polygon(12% 8%, 55% 0%, 88% 18%, 100% 55%, 78% 100%, 40% 92%, 6% 70%, 0% 30%);
}
.hero-gap {
  width: 64px;
  background: color-mix(in srgb, var(--accent) 12%, transparent);
  display: flex;
  align-items: center;
  justify-content: center;
  writing-mode: vertical-rl;
  font-weight: 700;
  color: var(--accent-text);
  font-size: 0.85rem;
  letter-spacing: 0.1em;
  border-left: 1px dashed var(--accent);
  border-right: 1px dashed var(--accent);
}
.hero h1 {
  font-size: clamp(1.8rem, 1.2rem + 2.6vw, 3rem);
  max-width: 20ch;
  margin-bottom: var(--space-2);
}
.hero .lead { font-size: 1.15rem; max-width: 62ch; margin-bottom: var(--space-2); }
.hero .fine-print { max-width: 60ch; margin-bottom: var(--space-4); }
.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-bottom: var(--space-5);
}
.scroll-cue {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-muted);
  font-size: 0.85rem;
}
.scroll-cue .chevron {
  animation: bounce 1.6s infinite;
}
@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(6px); }
}
@media (prefers-reduced-motion: reduce) {
  .scroll-cue .chevron { animation: none; }
}

/* ==========================================================================
   S1 — Quadrant
   ========================================================================== */
.quadrant-axes {
  display: grid;
  grid-template-columns: 40px 1fr;
  grid-template-rows: auto 1fr;
  gap: var(--space-2);
  margin-bottom: var(--space-2);
}
.axis-x {
  grid-column: 2;
  display: flex;
  justify-content: space-between;
  font-size: 0.85rem;
  color: var(--text-muted);
  padding: 0 4px;
}
.axis-y {
  grid-column: 1;
  grid-row: 2;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  align-items: center;
  font-size: 0.85rem;
  color: var(--text-muted);
  writing-mode: vertical-rl;
}
.axis-title {
  text-align: center;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: var(--space-1);
}
.quadrant-grid {
  grid-column: 2;
  grid-row: 2;
  display: grid;
  grid-template-columns: 1fr 1fr;
  grid-template-rows: 1fr 1fr;
  grid-template-areas:
    "tl tr"
    "bl br";
  gap: var(--space-2);
  min-height: 420px;
}
.q-cell {
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--border);
  border-left-width: 6px;
  padding: var(--space-3);
  text-align: left;
  transition: transform var(--transition-fast), opacity var(--transition-fast), box-shadow var(--transition-fast);
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.q-cell:hover, .q-cell:focus-visible { box-shadow: var(--shadow); }
.q-cell-toggle {
  display: block;
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  padding: 0;
  color: inherit;
  font: inherit;
  cursor: pointer;
}
.q-cell[data-cell="unknown-known"] { grid-area: tl; border-left-color: var(--q-unknown-known); }
.q-cell[data-cell="known-known"] { grid-area: tr; border-left-color: var(--q-known-known); }
.q-cell[data-cell="unknown-unknown"] { grid-area: bl; border-left-color: var(--q-unknown-unknown); }
.q-cell[data-cell="known-unknown"] { grid-area: br; border-left-color: var(--q-known-unknown); }

.q-cell .q-icon { font-size: 1.3rem; }
.q-cell[data-cell="known-known"] .q-title { color: var(--q-known-known); }
.q-cell[data-cell="known-unknown"] .q-title { color: var(--q-known-unknown); }
.q-cell[data-cell="unknown-known"] .q-title { color: var(--q-unknown-known); }
.q-cell[data-cell="unknown-unknown"] .q-title { color: var(--q-unknown-unknown); }
.q-title { font-weight: 700; font-size: 1.05rem; }
.q-title .en { font-weight: 400; color: var(--text-muted); font-size: 0.85rem; display: block; }
.q-oneliner { color: var(--text); font-size: 0.95rem; }
.q-detail {
  overflow: hidden;
  max-height: 0;
  transition: max-height var(--transition-med);
}
.q-cell.is-open .q-detail { max-height: 320px; }
.q-detail-inner { padding-top: 8px; border-top: 1px dashed var(--border); margin-top: 4px; }
.q-detail p { font-size: 0.9rem; }
.q-tactic { font-weight: 600; }
.q-jump {
  align-self: flex-start;
  font-size: 0.85rem;
  color: var(--accent-text);
  margin-top: auto;
}
.q-jump:hover { text-decoration: underline; }

.quadrant-grid.has-active .q-cell:not(.is-open) { opacity: 0.45; transform: scale(0.98); }

.quadrant-statement {
  font-size: 1.15rem;
  font-weight: 600;
  max-width: 78ch;
  margin: var(--space-4) 0 var(--space-2);
  padding: var(--space-3);
  background: var(--surface-2);
  border-radius: var(--radius);
}
.quadrant-note { max-width: 78ch; color: var(--text-muted); }

/* ==========================================================================
   S2 — Why HTML
   ========================================================================== */
.compare-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: var(--space-3);
  align-items: center;
  margin: var(--space-4) 0;
}
.compare-card {
  border-radius: var(--radius);
  padding: var(--space-3);
  border: 1px solid var(--border);
  min-height: 200px;
  position: relative;
}
.compare-card .badge {
  position: absolute;
  top: 12px; right: 12px;
  font-size: 0.75rem;
  padding: 4px 10px;
  border-radius: 999px;
  background: var(--surface-2);
  color: var(--text-muted);
}
.compare-doc {
  background: var(--surface-2);
  color: var(--text-muted);
}
.compare-doc .fake-line {
  height: 10px;
  border-radius: 4px;
  background: var(--border);
  margin-bottom: 10px;
  filter: blur(0.4px);
  opacity: 0.7;
}
.compare-artifact {
  background: var(--surface);
}
.compare-artifact .fake-btn {
  display: inline-block;
  padding: 6px 14px;
  border-radius: 8px;
  background: var(--accent);
  color: var(--on-accent);
  font-size: 0.8rem;
  margin: 4px 6px 4px 0;
}
.compare-artifact .fake-chip {
  display: inline-block;
  padding: 4px 10px;
  border-radius: 999px;
  border: 1px solid var(--border);
  font-size: 0.75rem;
  margin: 4px 6px 4px 0;
  color: var(--text-muted);
}
.compare-arrow {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}
.compare-arrow .arrow-glyph { font-size: 1.8rem; color: var(--accent); }

.why-closing {
  font-size: 1.05rem;
  font-weight: 600;
  max-width: 76ch;
}
.series-details {
  margin-top: var(--space-4);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-2) var(--space-3);
}
.series-details summary {
  cursor: pointer;
  font-weight: 600;
}
.series-details p { margin-top: var(--space-2); color: var(--text-muted); }

/* ==========================================================================
   S3 — Timeline
   ========================================================================== */
.timeline {
  display: flex;
  gap: var(--space-3);
  overflow-x: auto;
  padding-bottom: var(--space-2);
}
.timeline-stage {
  flex: 1 1 0;
  min-width: 220px;
  border-radius: var(--radius);
  padding: var(--space-3);
  border: 1px solid var(--border);
  border-top-width: 6px;
  background: var(--surface);
}
.timeline-stage[data-stage="pre"] { border-top-color: var(--s-pre); }
.timeline-stage[data-stage="during"] { border-top-color: var(--s-during); }
.timeline-stage[data-stage="post"] { border-top-color: var(--s-post); }
.timeline-stage h3 { display: flex; align-items: baseline; gap: 8px; }
.timeline-stage .count { font-size: 0.85rem; color: var(--text-muted); font-weight: 400; }
.timeline-stage .tagline { color: var(--text-muted); font-size: 0.92rem; margin-bottom: var(--space-2); }
.badge-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}
.demo-badge {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: 999px;
  border: 2px solid var(--border);
  background: var(--surface-2);
  font-size: 0.85rem;
  font-weight: 600;
  transition: transform var(--transition-fast), border-color var(--transition-fast);
}
.demo-badge:hover, .demo-badge:focus-visible { transform: translateY(-2px); }
.demo-badge.is-current { transform: scale(1.12); }
.demo-badge .num { color: var(--text-muted); font-weight: 700; }
.demo-badge[data-quadrant="known-known"] { border-color: var(--q-known-known); }
.demo-badge[data-quadrant="known-unknown"] { border-color: var(--q-known-unknown); }
.demo-badge[data-quadrant="unknown-known"] { border-color: var(--q-unknown-known); }
.demo-badge[data-quadrant="unknown-unknown"] { border-color: var(--q-unknown-unknown); }

.timeline-note {
  margin-top: var(--space-3);
  font-weight: 600;
}

/* ==========================================================================
   S4 — Demos
   ========================================================================== */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  align-items: center;
  margin-bottom: var(--space-4);
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
}
.filter-group {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}
.filter-group .filter-label {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-right: 4px;
}
.chip {
  padding: 6px 14px;
  border-radius: 999px;
  border: 1px solid var(--border);
  font-size: 0.85rem;
  background: var(--surface-2);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: border-color var(--transition-fast), color var(--transition-fast), background var(--transition-fast);
}
.chip[aria-pressed="true"] {
  border-color: var(--accent);
  color: var(--accent-text);
  background: color-mix(in srgb, var(--accent) 14%, var(--surface));
}
.chip .dot {
  width: 10px; height: 10px;
  border-radius: 50%;
  display: inline-block;
}
.chip[data-quadrant="known-known"] .dot { background: var(--q-known-known); }
.chip[data-quadrant="known-unknown"] .dot { background: var(--q-known-unknown); }
.chip[data-quadrant="unknown-known"] .dot { background: var(--q-unknown-known); }
.chip[data-quadrant="unknown-unknown"] .dot { background: var(--q-unknown-unknown); }

.demo-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-3);
}
.demo-card {
  grid-column: span 1;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--border);
  border-left-width: 6px;
  overflow: hidden;
  transition: opacity var(--transition-fast), transform var(--transition-fast);
}
.demo-card[data-stage="pre"] { border-left-color: var(--s-pre); }
.demo-card[data-stage="during"] { border-left-color: var(--s-during); }
.demo-card[data-stage="post"] { border-left-color: var(--s-post); }
.demo-card.is-expanded { grid-column: 1 / -1; }
.demo-card.is-filtered-out { display: none; }

.demo-card-head {
  width: 100%;
  text-align: left;
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: var(--space-2);
  align-items: start;
  padding: var(--space-3);
}
.demo-num {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--text-muted);
  line-height: 1;
}
.demo-head-main .demo-name {
  font-weight: 700;
  font-size: 1.05rem;
  margin-bottom: 4px;
}
.demo-name .en { color: var(--text-muted); font-weight: 400; font-size: 0.85rem; }
.q-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.78rem;
  padding: 3px 10px;
  border-radius: 999px;
  border: 1px solid;
  margin-bottom: 8px;
}
.q-tag[data-quadrant="known-known"] { color: var(--q-known-known); border-color: var(--q-known-known); }
.q-tag[data-quadrant="known-unknown"] { color: var(--q-known-unknown); border-color: var(--q-known-unknown); }
.q-tag[data-quadrant="unknown-known"] { color: var(--q-unknown-known); border-color: var(--q-unknown-known); }
.q-tag[data-quadrant="unknown-unknown"] { color: var(--q-unknown-unknown); border-color: var(--q-unknown-unknown); }
.demo-oneliner { font-weight: 600; }
.demo-chevron {
  font-size: 1.2rem;
  color: var(--text-muted);
  transition: transform var(--transition-fast);
  align-self: center;
}
.demo-card[aria-expanded="true"] .demo-chevron,
.demo-card-head[aria-expanded="true"] .demo-chevron { transform: rotate(180deg); }

.demo-panel {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-med);
}
.demo-card.is-expanded .demo-panel {
  max-height: 4000px;
}
.demo-panel-inner {
  padding: 0 var(--space-3) var(--space-3);
  border-top: 1px solid var(--border);
}
.demo-panel-inner h4 {
  margin-top: var(--space-3);
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--text-muted);
}
.claude-block {
  border: 2px solid var(--accent);
  border-radius: var(--radius);
  padding: var(--space-2) var(--space-3);
  margin-top: var(--space-2);
  background: color-mix(in srgb, var(--accent) 6%, var(--surface));
}
.claude-block h4 {
  color: var(--accent-text);
  margin-top: 0;
}
.prompt-block {
  position: relative;
  margin-top: var(--space-2);
}
.prompt-block pre {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: var(--space-2);
  padding-top: 40px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  line-height: 1.6;
  white-space: pre-wrap;
  word-break: break-word;
}
.copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 6px 12px;
  font-size: 0.78rem;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
}
.copy-btn:hover { border-color: var(--accent); }
.copy-btn.is-copied {
  border-color: var(--accent);
  color: var(--accent-text);
}
.demo-extend ul { padding-left: 1.2em; list-style: disc; }
.demo-extend li { margin-bottom: 4px; }
.demo-footer {
  display: flex;
  justify-content: flex-end;
  margin-top: var(--space-3);
}
.demo-footer a {
  font-size: 0.85rem;
  color: var(--accent-text);
}
.demo-footer a:hover { text-decoration: underline; }

/* ==========================================================================
   S5 — Playbook
   ========================================================================== */
.playbook-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-3);
}
.playbook-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: var(--space-3);
  background: var(--surface);
}
.playbook-card .num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px; height: 28px;
  border-radius: 50%;
  background: var(--accent);
  color: var(--on-accent);
  font-weight: 700;
  font-size: 0.85rem;
  margin-bottom: var(--space-2);
}
.playbook-card .principle { font-weight: 700; margin-bottom: 6px; }
.playbook-card .elaboration { color: var(--text-muted); font-size: 0.92rem; }
.playbook-closing {
  margin-top: var(--space-4);
  font-size: 1.1rem;
  font-weight: 600;
  max-width: 76ch;
  padding: var(--space-3);
  border-left: 4px solid var(--accent);
  background: var(--surface-2);
  border-radius: 0 var(--radius) var(--radius) 0;
}

/* ==========================================================================
   S6 — Skill CTA
   ========================================================================== */
.skill-pipeline {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-2);
  margin: var(--space-4) 0;
}
.skill-stage {
  border-radius: var(--radius);
  border: 1px solid var(--border);
  border-top-width: 6px;
  padding: var(--space-3);
  background: var(--surface);
  position: relative;
}
.skill-stage[data-stage="pre"] { border-top-color: var(--s-pre); }
.skill-stage[data-stage="during"] { border-top-color: var(--s-during); }
.skill-stage[data-stage="post"] { border-top-color: var(--s-post); }
.skill-stage h4 { margin-bottom: 8px; }
.skill-stage .artifact {
  margin-top: 8px;
  font-size: 0.82rem;
  color: var(--accent-text);
}
.skill-arrow {
  display: none;
}
.skill-cta-actions { margin-top: var(--space-3); }
.skill-fineprint { color: var(--text-muted); font-size: 0.85rem; margin-top: var(--space-2); }

/* ==========================================================================
   S7 — Footer
   ========================================================================== */
.site-footer {
  border-top: 1px solid var(--border);
  padding-top: var(--section-pad);
  padding-bottom: var(--space-5);
}
.footer-links {
  display: flex;
  gap: var(--space-3);
  margin: var(--space-2) 0;
  flex-wrap: wrap;
}
.footer-links a { color: var(--accent-text); }
.footer-links a:hover { text-decoration: underline; }
.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: var(--space-4);
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* ==========================================================================
   Responsive
   ========================================================================== */

/* Tablet: 640–1023px */
@media (max-width: 1023px) {
  .progress-rail { display: none; }
  .demo-grid { grid-template-columns: repeat(2, 1fr); }
  .playbook-grid { grid-template-columns: repeat(2, 1fr); }
}

/* Mobile: < 640px */
@media (max-width: 639px) {
  .nav-toggle { display: inline-flex; align-items: center; justify-content: center; width: 40px; height: 40px; }
  .nav-links {
    position: absolute;
    top: var(--nav-h);
    left: 0; right: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    align-items: flex-start;
    padding: var(--space-2) var(--space-3);
    gap: var(--space-2);
    display: none;
  }
  .nav-links.is-open { display: flex; }

  .hero-illustration { height: 160px; }
  .hero-actions { flex-direction: column; align-items: stretch; }

  .quadrant-axes { grid-template-columns: 1fr; }
  .axis-y { display: none; }
  .quadrant-grid {
    grid-column: 1;
    grid-template-columns: 1fr;
    grid-template-areas:
      "tl"
      "tr"
      "bl"
      "br";
    min-height: 0;
  }

  .compare-row { grid-template-columns: 1fr; }
  .compare-arrow { transform: rotate(90deg); padding: var(--space-2) 0; }

  .demo-grid { grid-template-columns: 1fr; }
  .demo-card.is-expanded { grid-column: 1; }

  .playbook-grid { grid-template-columns: 1fr; }
  .skill-pipeline { grid-template-columns: 1fr; }
  .footer-bottom { flex-direction: column; align-items: flex-start; }
}

/* Reduced motion: make every remaining transition/animation instant */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
  .demo-panel.is-open,
  .demo-card.is-expanded .demo-panel {
    max-height: none;
  }
}

@media (min-width: 640px) and (max-width: 1023px) {
  .hero-actions { flex-wrap: wrap; }
}