:root {
  --bg: #f6f4ef;
  --bg-alt: #eeebe3;
  --card: #fffdf9;
  --ink: #1d1f24;
  --ink-2: #4a4f59;
  --ink-3: #7d828c;
  --line: #ddd8cc;
  --accent: #d9480f;
  --accent-ink: #fff;
  --accent-soft: #fbe3d6;
  --ok: #2b8a3e;
  --shadow: 0 1px 2px rgba(30, 25, 15, .06), 0 8px 24px -12px rgba(30, 25, 15, .18);
  --radius: 14px;
  --mono: "JetBrains Mono", "SFMono-Regular", Consolas, "Liberation Mono", ui-monospace, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", "Segoe UI", sans-serif;

  /* 魔方配色 */
  --c-U: #ffd400;
  --c-D: #f5f5f2;
  --c-F: #00a05a;
  --c-B: #0b5bd3;
  --c-R: #ff6c0a;
  --c-L: #d3203b;
  --c-mute: #a9adb4;
  --plastic: #17181c;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #14161a;
    --bg-alt: #1a1d22;
    --card: #1f2228;
    --ink: #eceae4;
    --ink-2: #b5b8bf;
    --ink-3: #868a93;
    --line: #2e323a;
    --accent: #ff7a3d;
    --accent-ink: #1a1206;
    --accent-soft: #3a2418;
    --ok: #51cf66;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 10px 30px -14px rgba(0, 0, 0, .6);
    --c-mute: #4c515a;
    --plastic: #0b0c0e;
  }
}
:root[data-theme="dark"] {
  --bg: #14161a; --bg-alt: #1a1d22; --card: #1f2228; --ink: #eceae4; --ink-2: #b5b8bf; --ink-3: #868a93;
  --line: #2e323a; --accent: #ff7a3d; --accent-ink: #1a1206; --accent-soft: #3a2418; --ok: #51cf66; --c-mute: #4c515a; --plastic: #0b0c0e;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 72px; -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--bg); color: var(--ink);
  font: 16px/1.75 var(--sans); -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
h1, h2, h3 { line-height: 1.25; margin: 0; letter-spacing: -.01em; }
p { margin: 0 0 .9em; }
a { color: inherit; }
code, kbd { font-family: var(--mono); }
code {
  font-size: .92em; background: var(--bg-alt); border: 1px solid var(--line);
  padding: .05em .4em; border-radius: 6px; white-space: nowrap;
}
.wrap { max-width: 1140px; margin: 0 auto; padding: 0 24px; }
.muted { color: var(--ink-3); }

/* ---------- buttons ---------- */
.btn {
  appearance: none; border: 1px solid var(--line); background: var(--card); color: var(--ink);
  font: 600 15px/1 var(--sans); padding: 12px 18px; border-radius: 10px; cursor: pointer;
  text-decoration: none; display: inline-flex; align-items: center; gap: 8px;
  transition: transform .12s, background .15s, border-color .15s;
}
.btn:hover { border-color: var(--ink-3); }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn-primary:hover { border-color: var(--accent); filter: brightness(1.06); }
.btn-ghost { background: transparent; }
.btn-sm { padding: 7px 12px; font-size: 13px; border-radius: 8px; }
button:focus-visible, a:focus-visible, input:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: saturate(1.4) blur(10px); -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid transparent; transition: border-color .2s;
}
body.scrolled .topbar { border-bottom-color: var(--line); }
.topbar-in { display: flex; align-items: center; height: 60px; gap: 24px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; text-decoration: none; font-size: 17px; }
.brand-mark { display: grid; grid-template-columns: repeat(3, 7px); gap: 2px; padding: 3px; background: var(--plastic); border-radius: 5px; }
.brand-mark i { width: 7px; height: 7px; border-radius: 1.5px; background: var(--c-U); }
.brand-mark i:nth-child(2), .brand-mark i:nth-child(6) { background: var(--c-F); }
.brand-mark i:nth-child(4), .brand-mark i:nth-child(8) { background: var(--c-R); }
.brand-mark i:nth-child(5) { background: var(--c-D); }
.brand-mark i:nth-child(9) { background: var(--c-B); }
.nav { margin-left: auto; display: flex; gap: 4px; }
.nav a { text-decoration: none; font-size: 15px; color: var(--ink-2); padding: 6px 12px; border-radius: 8px; }
.nav a:hover { color: var(--ink); background: var(--bg-alt); }
.nav a.active { color: var(--ink); background: var(--bg-alt); font-weight: 600; }
.nav-toggle { display: none; margin-left: auto; width: 40px; height: 40px; border: 0; background: none; cursor: pointer; position: relative; }
.nav-toggle span { position: absolute; left: 10px; right: 10px; height: 2px; background: var(--ink); transition: transform .2s; }
.nav-toggle span:first-child { top: 15px; }
.nav-toggle span:last-child { top: 23px; }
body.nav-open .nav-toggle span:first-child { transform: translateY(4px) rotate(45deg); }
body.nav-open .nav-toggle span:last-child { transform: translateY(-4px) rotate(-45deg); }

/* ---------- hero ---------- */
.hero { padding: 56px 0 72px; }
.hero-in { display: grid; grid-template-columns: 1.05fr 1fr; gap: 40px; align-items: center; }
.eyebrow { color: var(--accent); font-weight: 700; font-size: 14px; letter-spacing: .08em; margin-bottom: 14px; }
.hero h1 { font-size: clamp(34px, 5.2vw, 56px); font-weight: 800; margin-bottom: 20px; }
.lead { font-size: 18px; color: var(--ink-2); max-width: 34em; }
.hero-cta { display: flex; gap: 12px; margin: 28px 0 36px; flex-wrap: wrap; }
.hero-facts { list-style: none; padding: 0; margin: 0; display: flex; gap: 36px; flex-wrap: wrap; }
.hero-facts li { display: flex; flex-direction: column; }
.hero-facts b { font-size: 24px; font-variant-numeric: tabular-nums; }
.hero-facts span { color: var(--ink-3); font-size: 14px; }
.hero-cube-box { text-align: center; }
.hero-cube { width: 100%; max-width: 460px; aspect-ratio: 1; margin: 0 auto; }
.hint { color: var(--ink-3); font-size: 13px; margin: 6px 0 0; }

/* ---------- cube view ---------- */
.cv { position: relative; perspective: 1000px; touch-action: none; cursor: grab; user-select: none; -webkit-user-select: none; }
.cv.dragging { cursor: grabbing; }
.cv-stage { position: absolute; left: 50%; top: 50%; width: 0; height: 0; transform-style: preserve-3d; }
.cv-cube { position: absolute; transform-style: preserve-3d; }
.cv-cubie { position: absolute; width: 60px; height: 60px; left: -30px; top: -30px; transform-style: preserve-3d; }
.cv-face { position: absolute; inset: 0; background: var(--plastic); backface-visibility: hidden; -webkit-backface-visibility: hidden; }
.cv-st { position: absolute; inset: 3.5px; border-radius: 7px; box-shadow: inset 0 0 0 1px rgba(0, 0, 0, .08), inset 0 -6px 10px rgba(0, 0, 0, .06); }
.c-U { background: var(--c-U); } .c-D { background: var(--c-D); }
.c-F { background: var(--c-F); } .c-B { background: var(--c-B); }
.c-R { background: var(--c-R); } .c-L { background: var(--c-L); }
.c-mute { background: var(--c-mute); }
.cv-box { width: 100%; aspect-ratio: 1; }

/* ---------- sections ---------- */
.sec { padding: 88px 0; }
.sec-alt { background: var(--bg-alt); }
.sec-head { max-width: 720px; margin-bottom: 40px; }
.sec-no { font: 700 13px/1 var(--mono); color: var(--accent); letter-spacing: .1em; margin-bottom: 10px; }
.sec-head h2 { font-size: clamp(28px, 3.6vw, 38px); font-weight: 800; margin-bottom: 12px; }
.sec-lead { color: var(--ink-2); font-size: 17px; margin: 0; }

/* basics */
.pieces { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.piece-card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px 22px 18px; box-shadow: var(--shadow); }
.mini-cube { width: 100%; max-width: 210px; aspect-ratio: 1; margin: 0 auto 8px; }
.piece-card h3 { font-size: 19px; margin-bottom: 8px; display: flex; align-items: center; gap: 8px; }
.piece-card p { color: var(--ink-2); font-size: 15px; margin: 0; }
.tag { font-size: 12px; font-weight: 600; color: var(--accent); background: var(--accent-soft); padding: 2px 8px; border-radius: 99px; }
.callout { margin-top: 24px; display: flex; gap: 22px; align-items: center; background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px 24px; }
.callout h3 { font-size: 17px; margin-bottom: 4px; }
.callout p { margin: 0; color: var(--ink-2); font-size: 15px; }
.callout-swatches { display: grid; grid-template-columns: repeat(2, 22px); gap: 4px; padding: 6px; background: var(--plastic); border-radius: 8px; flex: none; }
.sw { width: 22px; height: 22px; border-radius: 5px; }

/* notation */
.notation { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; align-items: start; }
.rule { display: flex; gap: 16px; align-items: flex-start; margin-bottom: 14px; }
.rule p { margin: 0; color: var(--ink-2); }
.rule-k { flex: none; min-width: 52px; text-align: center; font: 700 20px/1 var(--mono); background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 12px 8px; }
.face-table { border-collapse: collapse; margin: 22px 0 18px; width: 100%; background: var(--card); border-radius: 10px; overflow: hidden; border: 1px solid var(--line); }
.face-table th, .face-table td { padding: 10px 14px; border-bottom: 1px solid var(--line); text-align: left; font-size: 15px; }
.face-table tr:last-child th, .face-table tr:last-child td { border-bottom: 0; }
.face-table th { font-family: var(--mono); width: 44px; color: var(--accent); }
.note { font-size: 14.5px; color: var(--ink-2); border-left: 3px solid var(--line); padding-left: 14px; }
.notation-demo { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px 18px; box-shadow: var(--shadow); position: sticky; top: 84px; }
.notation-cube { max-width: 340px; margin: 0 auto; }
.notation-caption { text-align: center; color: var(--ink-2); font-size: 15px; min-height: 1.75em; margin: 12px 0 0; }
.move-pad { display: grid; grid-template-columns: repeat(6, 1fr); gap: 6px; }
.mv-btn {
  font: 600 15px/1 var(--mono); padding: 10px 0; border-radius: 8px; border: 1px solid var(--line);
  background: var(--bg); color: var(--ink); cursor: pointer; transition: background .12s, transform .1s;
}
.mv-btn:hover { background: var(--accent-soft); border-color: var(--accent); }
.mv-btn:active { transform: scale(.96); }
.mv-reset { display: flex; align-items: center; justify-content: center; }
.mv-reset svg { width: 18px; height: 18px; }

/* steps */
.step-index { list-style: none; padding: 0; margin: 0 0 40px; display: flex; flex-wrap: wrap; gap: 8px; }
.step-index a { display: inline-flex; align-items: center; gap: 8px; text-decoration: none; background: var(--card); border: 1px solid var(--line); border-radius: 99px; padding: 6px 14px 6px 6px; font-size: 14.5px; font-weight: 600; }
.step-index a:hover { border-color: var(--accent); }
.step-index span { width: 24px; height: 24px; border-radius: 50%; background: var(--ink); color: var(--bg); display: grid; place-items: center; font: 700 12px/1 var(--mono); }
.step { border-top: 1px solid var(--line); padding: 44px 0 52px; }
.step-head { display: flex; gap: 18px; align-items: flex-start; margin-bottom: 24px; }
.step-no { flex: none; width: 48px; height: 48px; border-radius: 12px; background: var(--accent); color: var(--accent-ink); display: grid; place-items: center; font: 800 22px/1 var(--mono); }
.step-head h3 { font-size: 26px; font-weight: 800; margin-bottom: 4px; }
.step-goal { color: var(--ink-2); margin: 0; }
.step-body { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr); gap: 40px; align-items: start; }
.prose ul { padding-left: 1.2em; margin: 0 0 1em; }
.prose li { margin-bottom: .45em; }
.prose li code { white-space: normal; }
.tip { background: var(--accent-soft); border-radius: 10px; padding: 12px 16px; font-size: 15px; }
.alg-big { margin: 4px 0 18px; }
.alg-big code { font-size: 20px; font-weight: 700; padding: 10px 16px; display: inline-block; border-radius: 10px; background: var(--card); white-space: normal; }
.shape-list { list-style: none; padding: 0 !important; }
.shape-list li { display: flex; align-items: center; gap: 12px; }
.shape { flex: none; display: grid; grid-template-columns: repeat(3, 9px); gap: 2px; padding: 3px; background: var(--plastic); border-radius: 5px; }
.shape i { width: 9px; height: 9px; border-radius: 2px; background: var(--c-mute); }
.shape i.y { background: var(--c-U); }
.demos { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 16px; }
.demo { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px 14px 12px; box-shadow: var(--shadow); min-height: 360px; display: flex; flex-direction: column; }
.demo-title { font-weight: 700; font-size: 15px; }
.demo-cube { max-width: 250px; margin: 2px auto; }
.demo-alg { display: flex; flex-wrap: wrap; gap: 4px; justify-content: center; margin: 6px 0 10px; }
.demo-alg .mv { font: 600 14px/1 var(--mono); padding: 6px 7px; border-radius: 6px; background: var(--bg); border: 1px solid var(--line); cursor: pointer; min-width: 30px; text-align: center; transition: background .15s, color .15s; }
.demo-alg .mv.done { background: var(--bg-alt); color: var(--ink-3); border-color: transparent; }
.demo-alg .mv.cur { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.demo.finished .demo-title::after { content: " ✓"; color: var(--ok); }
.demo-ctl { display: flex; justify-content: center; align-items: center; gap: 6px; margin-top: auto; }
.ic { width: 38px; height: 38px; border-radius: 10px; border: 1px solid var(--line); background: var(--bg); color: var(--ink); display: grid; place-items: center; cursor: pointer; padding: 0; }
.ic:hover { border-color: var(--ink-3); }
.ic svg { width: 18px; height: 18px; fill: none; stroke: currentColor; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.ic svg .fill { fill: currentColor; stroke: none; }
.ic-main { width: 46px; height: 46px; border-radius: 50%; background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.ic-main:hover { border-color: var(--accent); filter: brightness(1.06); }
.speed { font: 600 13px/1 var(--mono); width: 44px; height: 38px; border-radius: 10px; border: 1px solid var(--line); background: var(--bg); color: var(--ink-2); cursor: pointer; }

/* alg table */
.alg-table { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); }
.alg-row { display: grid; grid-template-columns: 140px 100px minmax(0, 1.4fr) minmax(0, 1fr) 40px; gap: 16px; align-items: center; padding: 14px 18px; border-bottom: 1px solid var(--line); }
.alg-row:last-child { border-bottom: 0; }
.alg-step { display: flex; align-items: center; gap: 8px; color: var(--ink-2); font-size: 14.5px; }
.alg-step i { font: 700 12px/1 var(--mono); font-style: normal; width: 22px; height: 22px; border-radius: 50%; background: var(--ink); color: var(--bg); display: grid; place-items: center; }
.alg-name { font-weight: 700; }
.alg-code { font: 600 16px/1.4 var(--mono); text-align: left; background: none; border: 1px dashed transparent; color: var(--ink); padding: 4px 8px; border-radius: 8px; cursor: copy; }
.alg-code:hover { border-color: var(--line); background: var(--bg); }
.alg-when { color: var(--ink-2); font-size: 14px; }

/* playground */
.play { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr); gap: 40px; align-items: start; }
.play-cube-col { text-align: center; position: sticky; top: 84px; }
.play-cube { max-width: 440px; margin: 0 auto; }
.play-status { display: inline-block; font-weight: 700; padding: 4px 14px; border-radius: 99px; background: var(--card); border: 1px solid var(--line); font-size: 14.5px; }
.play-status.ok { color: var(--ok); }
.play-panel { display: flex; flex-direction: column; gap: 20px; }
.move-pad-full { grid-template-columns: repeat(6, 1fr); }
.row-btns { display: flex; gap: 8px; flex-wrap: wrap; }
.alg-input label { display: block; font-weight: 700; font-size: 14px; margin-bottom: 6px; }
.alg-input-row { display: flex; gap: 8px; }
.alg-input input { flex: 1; min-width: 0; font: 500 16px/1 var(--mono); padding: 12px 14px; border-radius: 10px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }
.kbd-help p { font-size: 14px; color: var(--ink-2); margin: 0; }
kbd { display: inline-block; font-size: 12px; padding: 2px 6px; margin: 0 2px; border: 1px solid var(--line); border-bottom-width: 2px; border-radius: 5px; background: var(--card); line-height: 1.4; }
.history { display: flex; gap: 12px; align-items: center; background: var(--card); border: 1px solid var(--line); border-radius: 10px; padding: 10px 14px; }
.history-label { font-weight: 700; font-size: 13px; color: var(--ink-3); flex: none; }
.history-moves { display: flex; gap: 6px; overflow-x: auto; font: 500 14px/1.6 var(--mono); scrollbar-width: thin; white-space: nowrap; }

/* timer */
.timer { display: grid; grid-template-columns: minmax(0, 1.5fr) minmax(0, 1fr); gap: 28px; align-items: start; }
.timer-main, .timer-side { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; box-shadow: var(--shadow); }
.scramble-row { display: flex; gap: 12px; align-items: flex-start; }
.scramble { flex: 1; font-size: 18px; font-weight: 600; white-space: normal; word-spacing: .2em; line-height: 1.6; background: var(--bg); padding: 10px 14px; }
.timer-face {
  display: block; width: 100%; border: 0; background: none; color: var(--ink); cursor: pointer;
  font: 700 clamp(64px, 11vw, 120px)/1.1 var(--mono); font-variant-numeric: tabular-nums;
  padding: 40px 0 10px; user-select: none; -webkit-user-select: none; touch-action: manipulation; -webkit-tap-highlight-color: transparent;
}
.timer-face[data-state="hold"] { color: #e03131; }
.timer-face[data-state="ready"] { color: var(--ok); }
.timer-hint { text-align: center; color: var(--ink-3); font-size: 14px; }
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; margin-top: 18px; }
.stats div { background: var(--bg); border-radius: 10px; padding: 10px 12px; display: flex; flex-direction: column; }
.stats span { color: var(--ink-3); font-size: 12.5px; }
.stats b { font: 700 19px/1.3 var(--mono); }
.scramble-cube { max-width: 220px; margin: 0 auto; }
.timer-side .hint { text-align: center; }
.times-head { display: flex; justify-content: space-between; align-items: center; margin: 18px 0 8px; }
.times-head h3 { font-size: 16px; }
.times { list-style: none; padding: 0; margin: 0; max-height: 300px; overflow-y: auto; }
.times li { display: grid; grid-template-columns: 28px 70px minmax(0, 1fr) 24px; align-items: center; gap: 8px; padding: 6px 4px; border-bottom: 1px solid var(--line); font-size: 14px; }
.times li.empty { display: block; color: var(--ink-3); border: 0; }
.times .n { color: var(--ink-3); font: 12px var(--mono); }
.times b { font-family: var(--mono); }
.times .s { color: var(--ink-3); font: 11.5px var(--mono); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.times button { border: 0; background: none; color: var(--ink-3); cursor: pointer; font-size: 18px; line-height: 1; }
.times button:hover { color: #e03131; }
body.timing .topbar, body.timing .timer-side, body.timing .scramble-row, body.timing .stats { opacity: .15; transition: opacity .2s; }

/* next */
.next-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; }
.next-grid article { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px; }
.next-grid h3 { font-size: 17px; margin-bottom: 8px; }
.next-grid p { color: var(--ink-2); font-size: 15px; margin: 0; }

.foot { border-top: 1px solid var(--line); padding: 28px 0 40px; color: var(--ink-3); font-size: 14px; text-align: center; }
.foot p { margin: 0; }

.toast {
  position: fixed; left: 50%; bottom: 28px; transform: translate(-50%, 20px); opacity: 0; pointer-events: none;
  background: var(--ink); color: var(--bg); padding: 10px 18px; border-radius: 10px; font-size: 14.5px; z-index: 100;
  transition: opacity .2s, transform .2s; max-width: calc(100vw - 32px);
}
.toast.show { opacity: 1; transform: translate(-50%, 0); }

/* ---------- responsive ---------- */
@media (max-width: 960px) {
  .hero-in, .notation, .step-body, .play, .timer { grid-template-columns: 1fr; }
  .hero-cube { max-width: 360px; }
  .notation-demo, .play-cube-col { position: static; }
  .next-grid { grid-template-columns: repeat(2, 1fr); }
  .alg-row { grid-template-columns: 1fr auto; grid-template-areas: "step play" "name name" "code code" "when when"; gap: 4px 12px; }
  .alg-step { grid-area: step; } .alg-name { grid-area: name; } .alg-code { grid-area: code; padding-left: 0; }
  .alg-when { grid-area: when; } .alg-play { grid-area: play; }
}
@media (max-width: 760px) {
  .wrap { padding: 0 16px; }
  .nav-toggle { display: block; }
  .nav {
    position: absolute; top: 60px; left: 0; right: 0; flex-direction: column; gap: 0; padding: 8px 16px 16px;
    background: var(--bg); border-bottom: 1px solid var(--line); display: none;
  }
  body.nav-open .nav { display: flex; }
  .nav a { padding: 12px; font-size: 16px; }
  .hero { padding: 28px 0 48px; }
  .hero-in { gap: 8px; }
  .hero-cube-box { order: -1; }
  .hero-cube { max-width: 280px; }
  .sec { padding: 60px 0; }
  .pieces { grid-template-columns: 1fr; }
  .piece-card { display: grid; grid-template-columns: 110px 1fr; gap: 4px 14px; align-items: center; padding: 14px; }
  .piece-card .mini-cube { grid-row: span 2; width: 110px; margin: 0; }
  .callout { flex-direction: column; align-items: flex-start; }
  .next-grid { grid-template-columns: 1fr; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .move-pad-full { grid-template-columns: repeat(6, 1fr); gap: 4px; }
  .mv-btn { font-size: 13.5px; padding: 10px 0; }
  .step-head h3 { font-size: 22px; }
  .demos { grid-template-columns: 1fr; }
  .demo { min-height: 0; }
  .demo-cube { max-width: 230px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}