:root{--bg:#fbfaf7;--ink:#17202a;--mute:#5d6875;--line:#dcd8cf;--card:#fff;--accent:#0b6e63;--ok:#0b6e63;--no:#a23b2a}
@media(prefers-color-scheme:dark){:root{--bg:#0f1317;--ink:#e9edf1;--mute:#9aa6b2;--line:#2a333d;--card:#161c22;--accent:#5ee6d2;--ok:#5ee6d2;--no:#ff8f7a}}
*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font:18px/1.6 Georgia,'Times New Roman',serif}
header,main,footer{max-width:780px;margin:0 auto;padding:0 20px}header{padding-top:28px;display:flex;justify-content:space-between;align-items:baseline;gap:12px;flex-wrap:wrap}
header a.brand{font:700 22px system-ui,Segoe UI,Arial,sans-serif;color:var(--ink);text-decoration:none}nav a{font:15px system-ui,Segoe UI,Arial,sans-serif;margin-left:16px}
a{color:var(--accent)}h1{font:700 34px/1.2 system-ui,Segoe UI,Arial,sans-serif;margin:28px 0 10px}h2{font:700 22px/1.3 system-ui,Segoe UI,Arial,sans-serif;margin:34px 0 8px}
.mute{color:var(--mute)}.small{font:15px system-ui,Segoe UI,Arial,sans-serif}.video{position:relative;padding-top:56.25%;margin:20px 0;border-radius:12px;overflow:hidden;background:#000}
.video iframe{position:absolute;inset:0;width:100%;height:100%;border:0}.card{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:16px 18px;margin:14px 0}
ul.list{list-style:none;padding:0}ul.list li{border-bottom:1px solid var(--line);padding:12px 0}ul.list a{font:600 18px system-ui,Segoe UI,Arial,sans-serif;text-decoration:none}
.quiz fieldset{border:1px solid var(--line);border-radius:12px;margin:14px 0;padding:12px 16px}.quiz legend{font:600 17px system-ui,Segoe UI,Arial,sans-serif;padding:0 6px}
.quiz label{display:block;padding:6px 0;font:16px system-ui,Segoe UI,Arial,sans-serif;cursor:pointer}.quiz .why{font:15px system-ui,Segoe UI,Arial,sans-serif;margin:6px 0 0}
.quiz .right{color:var(--ok)}.quiz .wrong{color:var(--no)}button{font:600 16px system-ui,Segoe UI,Arial,sans-serif;background:var(--accent);color:var(--bg);border:0;border-radius:10px;padding:10px 18px;cursor:pointer}
.bar{height:10px;background:var(--line);border-radius:6px;overflow:hidden;margin:10px 0}.bar i{display:block;height:100%;background:var(--accent);width:0}
.lesson{display:flex;gap:12px;align-items:baseline}.lesson .n{font:700 15px system-ui,Segoe UI,Arial,sans-serif;color:var(--mute);min-width:26px}.done{color:var(--ok);font:600 14px system-ui,Segoe UI,Arial,sans-serif}
footer{padding:36px 20px 48px;color:var(--mute);font:14px system-ui,Segoe UI,Arial,sans-serif}