:root{
  --bg:#f6f8fc; --card:#ffffff; --ink:#1b2432; --muted:#64748b;
  --brand:#1d4ed8; --brand-dark:#1e40af; --ok:#15803d; --ok-bg:#dcfce7;
  --warn:#b45309; --line:#e2e8f0; --radius:14px;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg);color:var(--ink);line-height:1.55}
.topbar{background:var(--card);border-bottom:1px solid var(--line);position:sticky;top:0;z-index:10}
.topbar-inner{max-width:680px;margin:0 auto;padding:12px 16px;display:flex;align-items:center;justify-content:space-between;gap:8px}
.brand{font-weight:800;font-size:17px}
.topbar-right{display:flex;align-items:center;gap:10px}
.user-email{font-size:13px;color:var(--muted);max-width:38vw;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.screen{max-width:680px;margin:0 auto;padding:20px 16px 48px;min-height:70vh}
.foot{text-align:center;color:var(--muted);font-size:12px;padding:18px 12px 28px}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:18px;margin:0 0 14px}
.card h2{margin:0 0 6px;font-size:20px}
.card h3{margin:18px 0 8px;font-size:16px}
.muted{color:var(--muted);font-size:14px}
.center{text-align:center}
.btn{display:inline-block;border:0;border-radius:12px;padding:13px 18px;font-size:16px;font-weight:700;
  background:var(--brand);color:#fff;cursor:pointer;min-height:48px}
.btn:active{background:var(--brand-dark)}
.btn:disabled{opacity:.55;cursor:default}
.btn-block{width:100%}
.btn-ghost{background:transparent;color:var(--brand);padding:8px 10px;min-height:0;font-size:14px}
.btn-secondary{background:#e8eefc;color:var(--brand-dark)}
.row{display:flex;gap:10px}
.row .btn{flex:1}
label.field{display:block;margin:12px 0}
label.field span{display:block;font-size:14px;font-weight:600;margin-bottom:6px}
input[type=text],input[type=email],input[type=password]{
  width:100%;padding:13px 14px;font-size:16px;border:1.5px solid var(--line);border-radius:12px;background:#fff}
input:focus{outline:2px solid var(--brand);border-color:var(--brand)}
.error{background:#fef2f2;border:1px solid #fecaca;color:#b91c1c;border-radius:12px;padding:12px 14px;font-size:14px;margin:0 0 12px}
.tabs{display:flex;background:#eef2f7;border-radius:12px;padding:4px;margin-bottom:16px}
.tabs button{flex:1;border:0;background:transparent;padding:11px;border-radius:9px;font-size:15px;font-weight:700;color:var(--muted);cursor:pointer}
.tabs button.active{background:#fff;color:var(--ink);box-shadow:0 1px 3px rgba(0,0,0,.12)}
.list{display:flex;flex-direction:column;gap:10px}
.list-item{display:flex;align-items:center;justify-content:space-between;gap:10px;background:var(--card);
  border:1px solid var(--line);border-radius:var(--radius);padding:15px 16px;font-size:16px;font-weight:600;
  cursor:pointer;text-align:left;width:100%}
.list-item small{display:block;font-weight:400;color:var(--muted);font-size:13px}
.list-item .chev{color:var(--muted);font-size:18px;flex-shrink:0}
.back{background:none;border:0;color:var(--brand);font-size:15px;font-weight:700;cursor:pointer;padding:8px 0;margin-bottom:8px}
.unit{border:1px solid var(--line);border-radius:var(--radius);background:var(--card);margin-bottom:10px;overflow:hidden}
.unit-head{width:100%;background:none;border:0;display:flex;justify-content:space-between;align-items:center;
  padding:15px 16px;font-size:16px;font-weight:700;cursor:pointer;text-align:left}
.unit-head .n{background:#eef2ff;color:var(--brand-dark);border-radius:999px;font-size:12px;padding:3px 10px;margin-right:8px;white-space:nowrap}
.unit-body{display:none;border-top:1px solid var(--line)}
.unit.open .unit-body{display:block}
.unit.open .unit-head .chev{transform:rotate(90deg)}
.topic{display:flex;align-items:center;gap:12px;width:100%;background:none;border:0;border-bottom:1px solid var(--line);
  padding:13px 16px;font-size:15px;cursor:pointer;text-align:left}
.topic:last-child{border-bottom:0}
.topic .dot{width:26px;height:26px;border-radius:50%;border:2px solid var(--line);flex-shrink:0;
  display:flex;align-items:center;justify-content:center;font-size:14px;color:#fff}
.topic.done .dot{background:var(--ok);border-color:var(--ok)}
.topic .t{flex:1}
.topic .best{font-size:12px;color:var(--muted);white-space:nowrap}
.pill{display:inline-block;background:#eef2ff;color:var(--brand-dark);border-radius:999px;
  font-size:12px;font-weight:700;padding:4px 12px;margin:0 6px 6px 0}
.kv{background:#f8fafc;border:1px dashed var(--line);border-radius:12px;padding:12px 14px;margin:12px 0;font-size:14px}
.worked{background:#fffbeb;border:1px solid #fde68a;border-radius:12px;padding:14px 16px;margin:14px 0}
.worked h4{margin:0 0 8px;color:var(--warn);font-size:14px;text-transform:uppercase;letter-spacing:.04em}
.q{border-top:1px solid var(--line);padding:16px 0}
.q p.prompt{font-weight:600;margin:0 0 10px}
.opt{display:block;width:100%;text-align:left;background:#fff;border:1.5px solid var(--line);border-radius:12px;
  padding:12px 14px;font-size:15px;margin:0 0 8px;cursor:pointer}
.opt.sel{border-color:var(--brand);background:#eff6ff}
.opt.right{border-color:var(--ok);background:var(--ok-bg)}
.opt.wrong{border-color:#ef4444;background:#fef2f2}
.opt:disabled{cursor:default;opacity:1}
.ans{background:#f8fafc;border-radius:12px;padding:12px 14px;font-size:14px;margin-top:10px}
.ans summary{cursor:pointer;font-weight:700;color:var(--brand-dark)}
.score{background:var(--ok-bg);border:1px solid #bbf7d0;color:#14532d;border-radius:12px;padding:12px 14px;font-weight:700;margin:12px 0}
.spin{text-align:center;color:var(--muted);padding:40px 0}
a{color:var(--brand)}
@media (min-width:700px){ .brand{font-size:19px} }