:root{
  --bg:#0b0d12;
  --card:#131826;
  --muted:#a6b0bf;
  --text:#e7eef7;
  --border:rgba(255,255,255,.10);
  --shadow: 0 16px 30px rgba(0,0,0,.35);
  --accent:#22c55e;
  --accent2:#7c3aed;
}
*{box-sizing:border-box}
body{
  margin:0;
  min-height:100vh;
  background: radial-gradient(900px 520px at 20% 20%, rgba(34,197,94,.18), transparent 60%),
              radial-gradient(900px 520px at 80% 20%, rgba(124,58,237,.14), transparent 55%),
              var(--bg);
  color:var(--text);
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial;
}
.wrap{width:min(1100px, calc(100% - 24px)); margin:0 auto; padding:16px}
.top{display:flex; justify-content:space-between; align-items:flex-end; gap:14px; flex-wrap:wrap}
h1{margin:0 0 6px 0; font-size:28px}
.muted{color:var(--muted)}
.card{
  margin-top:14px;
  background:rgba(19,24,38,.92);
  border:1px solid var(--border);
  border-radius:18px;
  padding:16px;
  box-shadow: var(--shadow);
}
.hud{display:flex; gap:10px; align-items:center; flex-wrap:wrap}
.chip{background:rgba(255,255,255,.06); border:1px solid var(--border); border-radius:999px; padding:8px 10px; font-weight:800}
.btn{cursor:pointer; border:1px solid rgba(34,197,94,.35); background:rgba(34,197,94,.16); color:var(--text); border-radius:12px; padding:9px 12px; font-weight:900}
.btn:hover{filter:brightness(1.04)}
.q__title{font-weight:1000; margin-bottom:10px}
.q__expr{font-size:44px; font-weight:1000; letter-spacing:-.02em}
.options{margin-top:14px; display:grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap:12px}
@media (min-width:860px){ .options{grid-template-columns: repeat(4, minmax(0,1fr));} }
.opt{cursor:pointer; border:1px solid rgba(255,255,255,.12); background:rgba(255,255,255,.05); color:var(--text); border-radius:16px; padding:18px 10px; font-weight:1000; font-size:22px}
.opt:hover{filter:brightness(1.05)}
.msg{min-height:24px; margin-top:12px; font-weight:1000}
.msg.ok{color:#34d399}
.msg.err{color:#fb7185}
.tips{display:flex; gap:10px; align-items:center; margin-top:14px; flex-wrap:wrap}
.badge{display:inline-flex; align-items:center; gap:6px; padding:6px 10px; border-radius:999px; background:rgba(124,58,237,.12); border:1px solid rgba(124,58,237,.25); font-weight:900}