:root{
  --paper:#F2F0EB;
  --field:#8B8B8B;
  --ink:#0A0A0A;
  --muted:#6B6E70;
  --line:#E6E2DB;
  --blue:#0000FF;
  --radius:12px;
  --max:1120px;
  --sans:-apple-system,BlinkMacSystemFont,"Inter","SF Pro",Helvetica,Arial,sans-serif;
  --mono:ui-monospace,SFMono-Regular,Menlo,Monaco,monospace;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}
body{margin:0;font-family:var(--sans);color:var(--ink);background:var(--paper);line-height:1.5;-webkit-font-smoothing:antialiased}
a{color:inherit}
a:focus-visible,button:focus-visible{outline:2px solid var(--blue);outline-offset:2px}
img,video{display:block;max-width:100%}

.site-header{
  position:sticky;top:0;z-index:20;
  display:flex;align-items:center;gap:18px;
  padding:12px 18px;
  background:rgba(242,240,235,.92);
  backdrop-filter:blur(8px);
  border-bottom:1px solid var(--line);
}
.brand{display:flex;align-items:center;gap:10px;font-weight:650;letter-spacing:-.02em;text-decoration:none}
.brand-mark{width:20px;height:20px;border-radius:4px;background:var(--blue);display:inline-block}
.toc{margin-left:auto;display:flex;gap:14px;flex-wrap:wrap}
.toc a{font-size:13px;color:var(--muted);text-decoration:none;padding:4px 0;border-bottom:2px solid transparent}
.toc a.is-active,.toc a:hover{color:var(--ink);border-color:var(--ink)}
.progress{position:absolute;left:0;right:0;bottom:-1px;height:2px;background:transparent}
.progress span{display:block;height:100%;width:0;background:var(--ink);transition:width .2s}

.slide{max-width:var(--max);margin:0 auto;padding:56px 18px 48px;border-bottom:1px solid var(--line)}
.slide:last-of-type{border-bottom:none}
.section-head{max-width:660px;margin:0 0 24px}
.section-head h2{margin:0 0 8px;font-size:27px;line-height:1.15;letter-spacing:-.03em;font-weight:650}
.section-head p{margin:0;color:var(--muted)}

.cover .cover-grid{display:grid;grid-template-columns:1.05fr .95fr;gap:32px;align-items:center}
.cover h1{margin:0;font-size:50px;line-height:.92;letter-spacing:-.04em}
.lead{margin:10px 0 6px;font-size:17px}
.meta{margin:0;color:var(--muted);font-size:12px;font-family:var(--mono)}
.actions{margin-top:16px;display:flex;gap:10px;flex-wrap:wrap}
.btn{display:inline-flex;align-items:center;justify-content:center;padding:10px 16px;border-radius:999px;font-size:14px;font-weight:600;text-decoration:none;border:1px solid var(--line);background:#fff;color:var(--ink)}
.btn.primary{background:var(--ink);color:#fff;border-color:var(--ink)}
.cover-card{margin:0;background:#fff;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.cover-card img{width:100%;aspect-ratio:4/3;object-fit:cover}
.cover-card figcaption{padding:10px 12px;font-size:11px;color:var(--muted);border-top:1px solid var(--line)}

/* grid demo */
.grid-demo{display:grid;grid-template-columns:320px 1fr;gap:16px;align-items:start}
.bento-mock{
  background:var(--field);padding:8px;border-radius:var(--radius);
  display:grid;grid-template-columns:1fr 1fr;grid-template-rows:1fr 1fr;gap:8px;aspect-ratio:1
}
.bento-mock .cell{border-radius:10px;display:grid;place-items:center;font-size:12px}
.bento-mock .cell.black{background:#000;color:#fff}
.bento-mock .cell.portrait{background:#A9C4D4}
.bento-mock .cell.chrome{background:linear-gradient(135deg,#C0C0C0,#E8E8E8)}
.bento-mock .cell.blue{background:var(--blue);color:#fff}
.bento-mock .star{font-size:28px}
.bento-mock .dots{width:40px;height:40px;border-radius:50%;border:2px solid #fff;position:relative}
.bento-mock .dots::before,.bento-mock .dots::after{content:"";position:absolute;width:8px;height:8px;background:#fff;border-radius:50%;top:50%;left:50%}

.specs{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin-top:14px}
.specs li{list-style:none;display:flex;justify-content:space-between;align-items:center;padding:10px 12px;background:#fff;border:1px solid var(--line);border-radius:10px;font-size:12px}
.specs code{font-family:var(--mono)}
.specs span{color:var(--muted)}

.grid-demo figure,.elements-grid,.material-grid figure{margin:0;background:#fff;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.grid-demo img{width:100%}

.elements-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}
.elem{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:14px}
.elem-preview{height:120px;border-radius:10px;display:grid;place-items:center;margin-bottom:10px;border:1px solid var(--line);overflow:hidden}
.elem-preview.black{background:#000;color:#fff}
.elem-preview.portrait{background:#8FB4C8}
.elem-preview.chrome{background:linear-gradient(135deg,#D0D0D0,#F0F0F0)}
.elem-preview.blue{background:var(--blue);color:#fff}
.elem-preview.phone{background:#F0F0F0}
.elem-preview.type{background:#000;color:#fff;display:grid;place-items:start;padding:16px;font-size:14px;line-height:1.2}
.elem h3{margin:0 0 4px;font-size:14px}
.elem p{margin:0;color:var(--muted);font-size:12px}
.glyph{font-size:32px}

.material-grid{display:grid;grid-template-columns:280px 1fr;gap:16px}
.palette{display:grid;gap:10px;background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:16px;align-content:start}
.chip{display:flex;align-items:center;gap:12px}
.chip::before{content:"";width:32px;height:32px;border-radius:8px;background:var(--c);border:1px solid var(--line);flex:none}
.chip span{font-family:var(--mono);font-size:12px}
.chip em{margin-left:auto;color:var(--muted);font-size:11px;font-style:normal}

.video-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin-bottom:20px}
.video-card{margin:0;background:#fff;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.video-card video{width:100%;aspect-ratio:2000/1332;background:#000}

.frames h3{margin:0 0 10px;font-size:15px}
.strip{display:grid;gap:8px;margin-bottom:12px}
.strip:nth-of-type(1){grid-template-columns:repeat(6,1fr)}
.strip:nth-of-type(2){grid-template-columns:repeat(4,1fr)}
.strip:nth-of-type(3){grid-template-columns:repeat(6,1fr)}
.strip figure{margin:0;background:#fff;border:1px solid var(--line);border-radius:10px;overflow:hidden}
.strip img{width:100%;aspect-ratio:2000/1332;object-fit:cover}
.strip figcaption{padding:6px 8px;font-size:10px;text-align:center;color:var(--muted);border-top:1px solid var(--line)}
.note{color:var(--muted);font-size:11px}

.site-footer{max-width:var(--max);margin:0 auto;padding:24px 18px 40px;display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap;color:var(--muted);font-size:11px;border-top:1px solid var(--line)}
.site-footer a{color:var(--ink)}

@media (max-width: 900px){
  .cover .cover-grid,.grid-demo,.material-grid,.elements-grid,.video-grid{grid-template-columns:1fr}
  .cover h1{font-size:38px}
  .elements-grid{grid-template-columns:1fr 1fr}
  .strip:nth-of-type(1),.strip:nth-of-type(3){grid-template-columns:repeat(3,1fr)}
}
@media (max-width: 580px){
  .site-header{padding:10px 14px}
  .slide{padding:36px 14px 32px}
  .section-head h2{font-size:22px}
  .elements-grid{grid-template-columns:1fr}
  .strip:nth-of-type(1),.strip:nth-of-type(3){grid-template-columns:repeat(2,1fr)}
}