:root{--bg:#f4f6f9;--card:#fff;--text:#1d2533;--muted:#6b7585;--pri:#c8102e;--pri2:#a50d26;--ok:#1f8a4c;--warn:#b26a00;--line:#e3e7ee}
*{box-sizing:border-box}
body{margin:0;font-family:system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;background:var(--bg);color:var(--text);line-height:1.5}
.wrap{max-width:960px;margin:0 auto;padding:24px 16px}
.card{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:24px;margin-bottom:16px}
.center{min-height:100vh;display:flex;align-items:center;justify-content:center;padding:16px}
.narrow{width:100%;max-width:440px}
h1{font-size:22px;margin:0 0 8px}h2{font-size:18px;margin:0 0 12px}
.muted{color:var(--muted);font-size:14px}
label{display:block;font-weight:600;margin:14px 0 6px;font-size:14px}
input,select{width:100%;padding:11px 12px;border:1px solid var(--line);border-radius:8px;font-size:16px}
input:focus{outline:2px solid var(--pri);border-color:transparent}
button{background:var(--pri);color:#fff;border:0;border-radius:8px;padding:11px 18px;font-size:15px;font-weight:600;cursor:pointer}
button:hover{background:var(--pri2)}button:disabled{opacity:.5;cursor:not-allowed}
button.ghost{background:transparent;color:var(--text);border:1px solid var(--line)}
button.sm{padding:6px 10px;font-size:13px}
.full{width:100%;margin-top:18px}
.err{color:var(--pri);font-size:14px;margin-top:10px;min-height:20px}
.warn{background:#fff5e6;border:1px solid #f3c27a;color:#6b4100;border-radius:10px;padding:16px;margin:16px 0}
.warn ul{margin:8px 0 0;padding-left:20px}
table{width:100%;border-collapse:collapse;font-size:14px}
th,td{text-align:left;padding:9px 8px;border-bottom:1px solid var(--line);vertical-align:top}
th{color:var(--muted);font-weight:600;font-size:12px;text-transform:uppercase}
.code{font-family:ui-monospace,Menlo,monospace;font-weight:700;letter-spacing:1px}
.tag{display:inline-block;padding:2px 8px;border-radius:99px;font-size:12px;font-weight:600}
.t-new{background:#e8f0fe;color:#1a4fb4}.t-doing{background:#fff5e6;color:var(--warn)}.t-done{background:#e6f5ec;color:var(--ok)}.t-bad{background:#fdeaea;color:var(--pri)}
.row{display:flex;gap:10px;flex-wrap:wrap;align-items:flex-end}.row>*{flex:1;min-width:140px}.row>button{flex:0 0 auto}
.tablewrap{overflow-x:auto}
/* exam */
.noselect{user-select:none;-webkit-user-select:none}
.bar{position:sticky;top:0;z-index:5;background:var(--text);color:#fff;padding:10px 16px;display:flex;justify-content:space-between;align-items:center;gap:12px}
.timer{font-family:ui-monospace,monospace;font-size:20px;font-weight:700}
.timer.low{color:#ff8a8a}
.q{background:var(--card);border:1px solid var(--line);border-radius:12px;padding:18px;margin-bottom:14px}
.q .num{font-size:12px;color:var(--muted);font-weight:700;text-transform:uppercase}
.q pre{white-space:pre-wrap;font-family:inherit;margin:6px 0 12px;font-size:16px}
.q pre code{font-family:ui-monospace,Menlo,monospace}
.opt{display:flex;gap:10px;align-items:flex-start;padding:10px 12px;border:1px solid var(--line);border-radius:8px;margin-top:8px;cursor:pointer}
.opt:hover{background:#fafbfc}.opt.sel{border-color:var(--pri);background:#fdf1f3}
.opt b{min-width:20px}.opt input{width:auto;margin-top:4px}
.score{font-size:56px;font-weight:800;color:var(--pri);margin:8px 0}
.hidden{display:none!important}