:root{--bg:#f6f7f9;--card:#fff;--fg:#1d2433;--muted:#667085;--line:#e3e6eb;--accent:#2457d6;--accent-soft:#e8eefc;--ok:#1a7f4b;--ok-soft:#e6f4ec;--err:#b42318;--err-soft:#fdecea;--radius:12px}
@media (prefers-color-scheme:dark){:root{--bg:#12151b;--card:#1b2029;--fg:#e6e9ef;--muted:#98a2b3;--line:#2c3340;--accent:#7aa2ff;--accent-soft:#1f2b45;--ok:#5cc98e;--ok-soft:#173326;--err:#ff8a80;--err-soft:#3a1d1b}}
*{box-sizing:border-box}html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--bg);color:var(--fg);font:16px/1.55 system-ui,-apple-system,"Segoe UI",Roboto,sans-serif}
a{color:var(--accent);text-decoration:none}a:hover{text-decoration:underline}
.bar{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;padding:12px 20px;background:var(--card);border-bottom:1px solid var(--line)}
.brand{font-weight:700;font-size:20px;color:var(--fg)}.brand span{font-weight:400;font-size:13px;color:var(--muted);margin-left:8px}
nav{display:flex;gap:16px;align-items:center}
main{max-width:1100px;margin:0 auto;padding:20px 16px 40px}
footer{text-align:center;color:var(--muted);font-size:12px;padding:20px}
h1{font-size:26px;margin:8px 0 12px;line-height:1.25}h2{font-size:19px;margin:28px 0 10px}h3{font-size:17px;margin:0 0 8px}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:18px}
.narrow{max-width:400px;margin:40px auto}
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:14px}
.course{display:flex;flex-direction:column;gap:6px}.course .btn{align-self:flex-start;margin-top:auto}
.muted{color:var(--muted)}.small{font-size:13px}.lead{font-size:17px;color:var(--muted);margin-top:0}
.crumbs{font-size:13px;color:var(--muted);margin:0}
.stack{display:grid;gap:12px}label{display:grid;gap:4px;font-size:14px;font-weight:500}
input,textarea,select{font:inherit;color:var(--fg);background:var(--bg);border:1px solid var(--line);border-radius:8px;padding:10px 12px;width:100%}
textarea{resize:vertical}input:focus,textarea:focus{outline:2px solid var(--accent);outline-offset:1px}
.check{display:flex;gap:8px;align-items:center;font-weight:400}.check input{width:auto}
.btn{display:inline-flex;align-items:center;justify-content:center;min-height:42px;padding:0 18px;border-radius:8px;border:1px solid var(--accent);background:var(--accent);color:#fff;font:inherit;font-weight:600;cursor:pointer;text-decoration:none!important}
.btn.ghost{background:transparent;color:var(--accent)}.btn.danger{background:var(--err);border-color:var(--err)}.btn:disabled{opacity:.6;cursor:wait}
button.link{background:none;border:0;color:var(--accent);font:inherit;cursor:pointer;padding:0}
.inline{display:inline}.actions{display:flex;gap:10px;flex-wrap:wrap;align-items:center;margin-top:18px}
.notice{padding:10px 14px;border-radius:8px;background:var(--accent-soft);margin:0 0 14px}.notice.ok{background:var(--ok-soft)}.notice.err{background:var(--err-soft);color:var(--err)}
.pill{display:inline-block;font-size:12px;font-weight:600;padding:2px 8px;border-radius:999px;background:var(--line);color:var(--muted);vertical-align:middle}.pill.ok{background:var(--ok-soft);color:var(--ok)}
.progress{-webkit-appearance:none;appearance:none;height:8px;border:0;border-radius:99px;overflow:hidden;min-width:80px;width:100%;vertical-align:middle;background:var(--line);color:var(--ok)}
.progress::-webkit-progress-bar{background:var(--line);border-radius:99px}.progress::-webkit-progress-value{background:var(--ok);border-radius:99px}.progress::-moz-progress-bar{background:var(--ok);border-radius:99px}
td .progress{width:90px}
ol.lessons{padding-left:22px;margin:12px 0}ol.lessons li{padding:6px 0}ol.lessons li.done a{color:var(--muted)}.tick{color:var(--ok);font-weight:700}
.lesson-grid{display:grid;grid-template-columns:minmax(0,1fr) 360px;gap:16px;align-items:start}
.lesson p,.lesson li{max-width:70ch}
.pager{display:flex;justify-content:space-between;gap:12px;margin-top:20px;padding-top:14px;border-top:1px solid var(--line);font-size:14px}
.tutor{position:sticky;top:12px}.tutor h2{margin-top:0}
.chat{display:grid;gap:8px;max-height:55vh;overflow-y:auto;margin:10px 0}
.msg{padding:8px 12px;border-radius:10px;font-size:15px}.msg p{margin:0 0 6px}.msg p:last-child{margin:0}.msg ul{margin:4px 0;padding-left:18px}
.msg.user{background:var(--accent-soft);justify-self:end;max-width:90%}.msg.assistant{background:var(--bg);border:1px solid var(--line)}
.question{border:1px solid var(--line);margin:0}.question legend{font-weight:600;padding:0 4px}
.option{display:flex;gap:8px;align-items:flex-start;font-weight:400;padding:8px;border-radius:8px}.option input{width:auto;margin-top:5px}
.option.right{background:var(--ok-soft)}.option.wrong{background:var(--err-soft)}
fieldset.ai{border:1px dashed var(--line);border-radius:8px;display:grid;gap:8px}
table{width:100%;border-collapse:collapse;font-size:15px}th,td{text-align:left;padding:8px 10px;border-bottom:1px solid var(--line);vertical-align:middle}th{color:var(--muted);font-weight:500;font-size:13px}
.scroll{overflow-x:auto}.nowrap{white-space:nowrap}
details{margin-top:12px}summary{cursor:pointer;list-style:none;display:inline-flex}summary::-webkit-details-marker{display:none}
details.danger{margin-top:28px}
@media (max-width:860px){.lesson-grid{grid-template-columns:1fr}.tutor{position:static}.brand span{display:none}h1{font-size:22px}.actions .btn{flex:1}}