:root{
  --ink:#0a0a0a; --muted:#56627a; --surface:#f4f6f8; --card:#fff; --band:#e7e9ee;
  --accent:#126ed3; --transcript-ink:#2b3240; --guide:#d4d4d4; --maxw:1040px; --gutter:32px;
  --font-display:Sentient,Georgia,"Times New Roman",serif;
  --font-body:Inter,-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  --font-mono:"Space Mono","Roboto Mono",ui-monospace,SFMono-Regular,Menlo,monospace;
}
@font-face{font-family:Inter;src:url(/learn/courses/assets/fonts/inter.woff2) format("woff2");font-weight:100 900;font-style:normal;font-display:swap}
@font-face{font-family:Sentient;src:url(/learn/courses/assets/fonts/sentient.woff2) format("woff2");font-weight:200 700;font-style:normal;font-display:swap}
@font-face{font-family:"Space Mono";src:url(/learn/courses/assets/fonts/space-mono-400.woff2) format("woff2");font-weight:400;font-display:swap}
@font-face{font-family:"Space Mono";src:url(/learn/courses/assets/fonts/space-mono-700.woff2) format("woff2");font-weight:700;font-display:swap}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;font-family:var(--font-body);color:var(--ink);background:var(--surface);line-height:1.6;font-size:17px;-webkit-font-smoothing:antialiased}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}
h1,h2,h3{font-family:var(--font-display);font-weight:500;line-height:1.14;letter-spacing:-.01em;color:var(--ink)}
/* page frame: faint dashed vertical guide lines a fixed distance from the viewport edges (Sonar brand) */
.page{margin-inline:var(--gutter);min-height:100vh;border-left:1px dashed var(--guide);border-right:1px dashed var(--guide)}
.eyebrow{display:flex;align-items:center;gap:.7em;font-family:var(--font-mono);font-size:.72rem;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);margin:0 0 12px}
.eyebrow::before{content:"";flex:0 0 auto;width:9px;height:9px;background:var(--accent)}
/* course (video) — full-screen, headerless experience */
main.course{max-width:var(--maxw);margin:0 auto;padding:56px 24px 96px}
.course h1{font-size:clamp(1.9rem,4vw,2.9rem);margin:0 0 18px}
.course .description{font-size:1.15rem;margin:0 0 30px;max-width:72ch;color:var(--muted)}
/* diagonal-hatch frame around the video (Sonar image treatment) */
.course .video-frame{background-image:repeating-linear-gradient(-45deg,var(--guide) 0 1px,transparent 1px 5.657px);border:1px solid var(--guide);padding:12px}
.course .video{position:relative;width:100%;aspect-ratio:16/9;overflow:hidden;background:#000}
.course .video iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.transcript{margin:48px 0 0;border-top:1px solid var(--band);padding-top:20px}
.transcript>summary{font-family:var(--font-mono);font-weight:700;font-size:.8rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);cursor:pointer;list-style:none;display:inline-flex;align-items:center;gap:9px;user-select:none}
.transcript>summary::-webkit-details-marker{display:none}
.transcript>summary::before{content:"\25B8";font-size:.95em;transition:transform .15s ease}
.transcript[open]>summary::before{transform:rotate(90deg)}
.transcript>summary:hover{color:var(--ink)}
.transcript p{color:var(--transcript-ink);max-width:72ch;margin:18px 0 0}
/* catalog (index) */
main.catalog{max-width:var(--maxw);margin:0 auto;padding:64px 24px 96px}
.catalog h1{font-size:clamp(2.2rem,5vw,3.2rem);margin:0 0 6px}
.catalog .sub{color:var(--muted);margin:0 0 44px;font-size:1.05rem}
.catalog h2{font-family:var(--font-mono);font-weight:700;font-size:.8rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);margin:44px 0 6px}
.catalog ul{list-style:none;margin:0;padding:0}
.catalog li{border-bottom:1px solid var(--band)}
.catalog li a{display:block;padding:14px 2px;color:var(--ink);font-size:1.06rem;transition:padding .12s ease,color .12s ease}
.catalog li a:hover{color:var(--accent);text-decoration:none;padding-left:10px}
.catalog .llms{margin:52px 0 0;color:var(--muted);font-size:.92rem;font-family:var(--font-mono)}
@media (max-width:960px){.page{border-left:0;border-right:0;margin-inline:0}}
@media (max-width:640px){body{font-size:16px}main.course,main.catalog{padding-left:18px;padding-right:18px}}