/* Shared site chrome for the System Design Foundations course.
   Lesson-player-specific styles stay inline in index.html. */
:root{--bg:#f5f8fc;--paper:#fff;--ink:#14213d;--muted:#5f6b7a;--brand:#315efb;--accent:#14b8a6;--warm:#ffb020;--line:#dce3ee;--soft:#eef3ff;--good:#087f5b;--bad:#c92a2a;--shadow:0 10px 28px rgba(24,39,75,.09)}
*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--ink);font:16px/1.55 Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",sans-serif}
.shell{max-width:1180px;margin:auto;padding:24px}
a{color:var(--brand)}

.sitenav{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:14px 24px;background:var(--paper);border-bottom:1px solid var(--line)}
.sitenav .brand{font-weight:800;font-size:1.05rem;color:var(--ink);text-decoration:none}
.sitenav .brand span{color:var(--brand)}
.sitenav-links{display:flex;gap:6px;flex-wrap:wrap}
.sitenav-links a{padding:8px 13px;border-radius:9px;color:var(--muted);text-decoration:none;font-size:.92rem;font-weight:650}
.sitenav-links a:hover{background:var(--soft);color:var(--ink)}
.sitenav-links a.active{background:var(--soft);color:var(--brand)}

.page-hero{padding:30px;background:linear-gradient(120deg,#14213d,#2546a8);color:#fff;border-radius:20px;margin:24px auto 18px;max-width:1180px}
.page-hero .eyebrow{text-transform:uppercase;letter-spacing:.12em;font-size:.76rem;font-weight:750;color:#a8c1ff}
.page-hero h1{margin:.3rem 0 .6rem;font-size:clamp(1.9rem,4.4vw,2.9rem);line-height:1.1}
.page-hero p{max-width:720px;margin:0;color:#d9e4ff}

.card{background:var(--paper);border:1px solid var(--line);box-shadow:var(--shadow);border-radius:18px}
.page-section{padding:28px;margin-bottom:18px}
.page-section h2{font-size:1.5rem;margin:0 0 10px}
.page-section h3.section-title{font-size:1.05rem;margin:22px 0 10px}
.page-section p{color:#334155;max-width:760px}
.page-section ul{color:#334155;max-width:760px;padding-left:1.2em}
.page-section li{margin:4px 0}

.mini{border:1px solid var(--line);border-radius:14px;padding:16px;background:#fbfcff}
.mini h3{font-size:1rem;margin:0 0 5px}
.mini p{margin:0;color:var(--muted)}
.grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:14px}

.phase-block{margin-bottom:26px}
.phase-block h3{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em;color:var(--brand);font-weight:800;margin:0 0 10px}
.lesson-row{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:13px 15px;border:1px solid var(--line);border-radius:12px;background:#fbfcff;margin-bottom:8px;text-decoration:none;color:var(--ink)}
.lesson-row:hover{border-color:var(--brand);background:var(--soft)}
.lesson-row .num{flex:none;height:26px;width:26px;display:grid;place-items:center;border-radius:50%;background:#e9edf5;color:var(--muted);font-size:.78rem;font-weight:700}
.lesson-row .txt{flex:1}
.lesson-row .txt strong{display:block;font-size:.96rem}
.lesson-row .txt span{font-size:.85rem;color:var(--muted)}
.lesson-row .time{flex:none;font-size:.8rem;color:var(--muted)}

.cta-row{display:flex;gap:12px;flex-wrap:wrap;margin-top:18px}
.btn{display:inline-block;font-weight:700;padding:11px 18px;border-radius:10px;text-decoration:none}
.btn.primary{background:var(--brand);color:#fff}
.btn.secondary{background:#e9edf5;color:var(--ink)}

.footer-note{font-size:.82rem;color:var(--muted);text-align:center;margin:18px 0}

@media(max-width:800px){
  .shell{padding:15px}
  .page-hero{padding:22px;margin:15px}
  .page-section{padding:20px}
  .grid{grid-template-columns:1fr}
  .sitenav{flex-wrap:wrap;padding:12px 15px}
}