:root {
  --bg: #0f1419;
  --panel: #1a222d;
  --panel2: #243041;
  --text: #e7eef7;
  --muted: #9aadc2;
  --accent: #3d9cf0;
  --good: #3ecf8e;
  --bad: #f07178;
  --warn: #e6c07b;
  --border: #2c3a4d;
  --radius: 14px;
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  background: radial-gradient(1200px 600px at 10% -10%, #1b3a5a 0%, transparent 55%),
              radial-gradient(900px 500px at 100% 0%, #1a2f28 0%, transparent 50%),
              var(--bg);
  color: var(--text);
}
#app { max-width: 820px; margin: 0 auto; padding: 24px 16px 48px; }
h1 { font-size: 1.45rem; margin: 0 0 6px; letter-spacing: -0.02em; }
.sub { color: var(--muted); margin: 0 0 22px; font-size: 0.95rem; line-height: 1.45; }
.card {
  background: color-mix(in srgb, var(--panel) 92%, black);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 18px 16px;
  margin-bottom: 14px;
  box-shadow: 0 10px 30px rgba(0,0,0,.25);
}
.row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
label { display: grid; gap: 6px; font-size: 0.82rem; color: var(--muted); min-width: 140px; flex: 1; }
select, button, .opt {
  font: inherit; color: var(--text);
}
select {
  background: var(--panel2);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 12px;
}
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  background: var(--panel2);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 8px 12px;
  cursor: pointer;
  color: var(--text);
}
.chip.active { border-color: var(--accent); background: #24486c; }
.btn {
  background: var(--accent);
  border: none;
  border-radius: 10px;
  padding: 12px 18px;
  cursor: pointer;
  font-weight: 600;
}
.btn.secondary { background: var(--panel2); border: 1px solid var(--border); }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.meta {
  display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap;
  color: var(--muted); font-size: 0.9rem; margin-bottom: 12px;
}
.timer.warn { color: var(--warn); font-weight: 700; }
.timer.danger { color: var(--bad); font-weight: 800; }
.progress {
  height: 8px; background: var(--panel2); border-radius: 999px; overflow: hidden; margin-bottom: 16px;
}
.progress > span { display: block; height: 100%; background: linear-gradient(90deg, #2f7fd4, #3ecf8e); }
.stem { font-size: 1.05rem; line-height: 1.55; margin: 0 0 14px; }
.opts { display: grid; gap: 8px; }
.opt {
  text-align: left;
  background: var(--panel2);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 14px;
  cursor: pointer;
  line-height: 1.4;
}
.opt:hover { border-color: #4d6480; }
.opt.selected { border-color: var(--accent); background: #1e3a55; }
.opt.correct { border-color: var(--good); background: #1a3d30; }
.opt.wrong { border-color: var(--bad); background: #3a2226; }
.nav { display: flex; gap: 10px; justify-content: space-between; margin-top: 16px; flex-wrap: wrap; }
.score {
  font-size: 2rem; font-weight: 750; margin: 8px 0 4px;
}
.small { color: var(--muted); font-size: 0.85rem; }
.review { border-top: 1px solid var(--border); margin-top: 14px; padding-top: 12px; }
.review-item { margin-bottom: 14px; }
.badge {
  display: inline-block; font-size: 0.75rem; padding: 2px 8px; border-radius: 999px;
  background: var(--panel2); color: var(--muted); margin-bottom: 6px;
}
.err { color: var(--bad); }