/* Atlas presentation — restrained, content-first */
:root{
  --paper:#F6F5F3;
  --paper-2:#EFEDE8;
  --ink:#111213;
  --muted:#6B6E70;
  --line:#E6E2DB;
  --sky:#7DD3F5;
  --sky-2:#5BC0E8;
  --radius:14px;
  --max:1120px;
  --sans:-apple-system,BlinkMacSystemFont,"Inter","SF Pro Display","Helvetica Neue",Arial,sans-serif;
  --mono:ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,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:1.55;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
a{color:inherit}
a:focus-visible,button:focus-visible{outline:2px solid var(--sky-2);outline-offset:2px}
img,video{display:block;max-width:100%}

/* header */
.site-header{
  position:sticky;top:0;z-index:20;
  display:flex;align-items:center;gap:20px;
  padding:14px 20px;
  background:rgba(246,245,243,.92);
  backdrop-filter:saturate(1.1) blur(8px);
  border-bottom:1px solid var(--line);
}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;font-weight:650;letter-spacing:-.02em}
.brand .mark{width:22px;height:22px;fill:var(--sky)}
.toc{margin-left:auto;display:flex;gap:14px;flex-wrap:wrap}
.toc a{
  font-size:13px;letter-spacing:-.01em;
  text-decoration:none;color:var(--muted);
  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}

/* slides */
.slide{
  max-width:var(--max);
  margin:0 auto;
  padding:56px 20px 48px;
  border-bottom:1px solid var(--line);
}
.slide:last-of-type{border-bottom:none}
.section-head{max-width:680px;margin:0 0 28px}
.section-head h2{
  margin:0 0 10px;
  font-size:28px;line-height:1.15;letter-spacing:-.03em;font-weight:650
}
.section-head p{margin:0;color:var(--muted);font-size:16px}

/* cover */
.cover .cover-grid{
  display:grid;grid-template-columns:1.05fr .95fr;gap:36px;align-items:center;
}
.cover h1{margin:0;font-size:54px;line-height:.95;letter-spacing:-.04em}
.lead{margin:10px 0 6px;font-size:18px;color:var(--ink)}
.meta{margin:0;color:var(--muted);font-size:13px;font-family:var(--mono)}
.actions{margin-top:18px;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)}
.btn.ghost:hover{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%;height:auto;aspect-ratio:4/3;object-fit:cover}
.cover-card figcaption{padding:10px 12px;font-size:12px;color:var(--muted);border-top:1px solid var(--line)}

/* grids */
.mark-grid,.type-grid,.ratio-grid,.image-grid,.system-grid{
  display:grid;gap:18px
}
.mark-grid{grid-template-columns:320px 1fr}
.type-grid{grid-template-columns:320px 1fr}
.ratio-grid{grid-template-columns:220px 1fr}
.image-grid{grid-template-columns:1fr 1fr;align-items:start}
.system-grid{grid-template-columns:280px 1fr}

.mark-tile,.type-spec,.ratio-list,.copy-block,.palette{
  background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:18px
}
.swatch{width:100%;aspect-ratio:1;background:var(--sky);border-radius:10px;display:grid;place-items:center;margin-bottom:14px}
.big-mark{width:72px;height:72px;fill:#fff}
dl{margin:0;display:grid;gap:10px}
dt{font-size:11px;letter-spacing:.08em;text-transform:uppercase;color:var(--muted)}
dd{margin:0;font-size:13px;color:var(--ink)}

.type-spec .weight{font-size:28px;line-height:1;letter-spacing:-.02em;padding:8px 0;border-bottom:1px solid var(--line)}
.type-spec .weight.light{font-weight:300}
.type-spec .weight.regular{font-weight:400}
.type-spec .weight.bold{font-weight:700}
.metrics{margin-top:14px;position:relative;height:110px;background:#fff;border:1px dashed var(--line);border-radius:10px;display:grid;place-items:center}
.metrics strong{font-size:48px;font-weight:300;letter-spacing:-.04em;opacity:.12}
.metrics div{position:absolute;left:12px;right:12px;display:flex;align-items:center;gap:8px}
.metrics div:nth-child(1){top:18px}
.metrics div:nth-child(2){top:48px}
.metrics div:nth-child(3){top:82px}
.metrics span{font-size:10px;color:var(--muted)}
.metrics i{flex:1;height:1px;background:var(--ink);opacity:.18}

.ratio-list{display:grid;gap:10px;align-content:start}
.ratio-list div{display:flex;justify-content:space-between;align-items:center;padding:10px 12px;border:1px solid var(--line);border-radius:10px}
.ratio-list code{font-family:var(--mono);font-size:13px}
.ratio-list span{font-size:12px;color:var(--muted)}

.image-grid figure,.mark-grid figure,.type-grid figure,.ratio-grid figure,.system-grid figure{
  margin:0;background:#fff;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden
}
.image-grid img,.mark-grid img,.type-grid img,.ratio-grid img,.system-grid img{width:100%;height:auto}
figcaption{padding:10px 12px;font-size:12px;color:var(--muted);border-top:1px solid var(--line)}

blockquote{margin:0;font-size:18px;line-height:1.4;letter-spacing:-.02em}
.spec{margin:8px 0 0;color:var(--muted);font-size:13px;font-family:var(--mono)}

.palette{display:grid;gap:12px}
.chip{display:flex;align-items:center;gap:12px}
.chip::before{content:"";width:36px;height:36px;border-radius:8px;background:var(--c);border:1px solid var(--line);flex:none}
.chip span{font-family:var(--mono);font-size:13px}
.chip em{margin-left:auto;font-size:12px;color:var(--muted);font-style:normal}

/* motion */
.video-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-bottom:22px}
.video-card{margin:0;background:#fff;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.video-card video{width:100%;height:auto;aspect-ratio:4/3;background:#000}

.frames h3{margin:0 0 12px;font-size:16px;letter-spacing:-.02em}
.strip{display:grid;grid-template-columns:repeat(6,1fr);gap:10px;margin-bottom:14px}
.strip figure{margin:0;background:#fff;border:1px solid var(--line);border-radius:10px;overflow:hidden}
.strip img{width:100%;aspect-ratio:4/3;object-fit:cover}
.strip figcaption{padding:6px 8px;font-size:11px;text-align:center}
.note{margin:8px 0 0;color:var(--muted);font-size:12px}

.site-footer{
  max-width:var(--max);margin:0 auto;padding:24px 20px 40px;
  display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap;
  color:var(--muted);font-size:12px;border-top:1px solid var(--line)
}
.site-footer a{color:var(--ink)}

/* responsive */
@media (max-width: 900px){
  .cover .cover-grid,
  .mark-grid,.type-grid,.ratio-grid,.image-grid,.system-grid,
  .video-grid{grid-template-columns:1fr}
  .cover h1{font-size:42px}
  .strip{grid-template-columns:repeat(3,1fr)}
}
@media (max-width: 580px){
  .site-header{padding:10px 14px}
  .toc{gap:10px}
  .toc a{font-size:12px}
  .slide{padding:36px 14px 32px}
  .section-head h2{font-size:24px}
  .strip{grid-template-columns:repeat(2,1fr)}
}