:root{color-scheme:light dark;--bg: #0f1115;--surface: #171a21;--card: #1e222b;--border: #2a3140;--text: #e8eaef;--muted: #9aa3b5;--accent: #4f8cff;--danger: #ff6b6b;font-family:Segoe UI,system-ui,-apple-system,sans-serif;line-height:1.5;color:var(--text);background:var(--bg)}*{box-sizing:border-box}body{margin:0;min-height:100vh}a{color:var(--accent);text-decoration:none}a:hover{text-decoration:underline}.page{max-width:960px;margin:0 auto;padding:1.25rem}.center{display:flex;align-items:center;justify-content:center;min-height:40vh}.muted{color:var(--muted)}.small{font-size:.875rem}.title{font-size:1.75rem;font-weight:600;margin:0 0 .5rem}.small-title{font-size:1.25rem}.topbar{display:flex;align-items:flex-start;justify-content:space-between;gap:1rem;margin-bottom:1.5rem}.card{background:var(--card);border:1px solid var(--border);border-radius:12px;padding:1.25rem}.auth-page{display:flex;align-items:center;justify-content:center;min-height:100vh}.auth-card{width:100%;max-width:400px}.stack{display:flex;flex-direction:column;gap:1rem;margin-top:1.25rem}.field{display:flex;flex-direction:column;gap:.35rem;font-size:.9rem}.field input{padding:.6rem .75rem;border-radius:8px;border:1px solid var(--border);background:var(--surface);color:var(--text)}.btn{border:none;border-radius:8px;padding:.65rem 1rem;font-weight:600;cursor:pointer;background:var(--border);color:var(--text)}.btn.primary{background:var(--accent);color:#fff}.btn.ghost{background:transparent;border:1px solid var(--border)}.btn:disabled{opacity:.6;cursor:not-allowed}.small-btn{font-size:.85rem;padding:.4rem .75rem;text-decoration:none;display:inline-block}.error-banner{background:#ff6b6b1f;border:1px solid var(--danger);color:#ffb4b4;padding:.75rem 1rem;border-radius:8px;margin-bottom:1rem}.modules{display:flex;flex-direction:column;gap:1rem}.module-head h2{margin:0 0 .35rem;font-size:1.1rem}.lesson-list{list-style:none;margin:1rem 0 0;padding:0;display:flex;flex-direction:column;gap:.5rem}.lesson-row{display:flex;align-items:center;justify-content:space-between;gap:.75rem;padding:.65rem .75rem;border-radius:8px;background:var(--surface);border:1px solid var(--border)}.lesson-row.locked{opacity:.65}.lesson-title{font-weight:500}.badge{font-size:.75rem;padding:.2rem .5rem;border-radius:6px;border:1px solid var(--border)}.muted-badge{color:var(--muted)}.lesson-layout .lesson-toolbar{display:flex;align-items:center;justify-content:space-between;margin-bottom:1rem}.link-back{font-size:.95rem}.lesson-desc{color:var(--muted);margin-top:0}.player-wrap{position:relative;width:100%;margin:1rem 0;border-radius:10px;overflow:hidden;border:1px solid var(--border);background:#000;aspect-ratio:16 / 9}.player-wrap iframe{width:100%;height:100%;border:0}.homework{margin-top:1rem;padding-top:1rem;border-top:1px solid var(--border)}.homework h3{margin:0 0 .5rem;font-size:1rem}.actions{margin-top:1.25rem}@media (max-width: 600px){.lesson-row{flex-direction:column;align-items:flex-start}}