:root {
  color-scheme: dark;
  --bg: #0b1020;
  --card: rgba(17, 24, 48, .82);
  --card-strong: rgba(25, 35, 68, .96);
  --text: #edf3ff;
  --muted: #aab7d4;
  --line: rgba(255,255,255,.12);
  --accent: #70e1ff;
  --accent-2: #9b8cff;
  --ok: #37d67a;
  --bad: #ff5b6e;
  --shadow: 0 24px 80px rgba(0,0,0,.45);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at top left, rgba(112,225,255,.18), transparent 32rem),
    radial-gradient(circle at bottom right, rgba(155,140,255,.20), transparent 30rem),
    var(--bg);
  color: var(--text);
}
.shell { width: min(980px, calc(100% - 32px)); margin: 0 auto; padding: 42px 0; }
.hero { text-align: center; margin-bottom: 22px; }
.eyebrow { margin: 0 0 8px; color: var(--accent); text-transform: uppercase; letter-spacing: .16em; font-size: 12px; font-weight: 800; }
h1 { margin: 0; font-size: clamp(38px, 7vw, 72px); line-height: .95; letter-spacing: -0.06em; }
.lead { max-width: 680px; margin: 18px auto 24px; color: var(--muted); font-size: clamp(16px, 2vw, 20px); }
.stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; max-width: 560px; margin: 0 auto 16px; }
.stats div { border: 1px solid var(--line); border-radius: 18px; padding: 14px; background: rgba(255,255,255,.05); }
.stats strong { display: block; font-size: 28px; }
.stats span { color: var(--muted); font-size: 13px; }
.progress-wrap { height: 12px; max-width: 560px; margin: 0 auto; background: rgba(255,255,255,.09); border-radius: 999px; overflow: hidden; border: 1px solid var(--line); }
.progress-bar { width: 0%; height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent-2)); transition: width .25s ease; }
.progress-text { margin: 8px 0 0; color: var(--muted); font-size: 14px; }
.card { background: var(--card); border: 1px solid var(--line); box-shadow: var(--shadow); border-radius: 30px; padding: clamp(22px, 4vw, 38px); backdrop-filter: blur(16px); }
.counter { color: var(--accent); font-weight: 800; margin-bottom: 12px; }
h2 { margin: 0 0 22px; font-size: clamp(24px, 4vw, 38px); line-height: 1.14; letter-spacing: -0.035em; }
.options { display: grid; gap: 12px; }
.option { width: 100%; display: grid; grid-template-columns: 46px 1fr; gap: 14px; align-items: center; text-align: left; color: var(--text); background: rgba(255,255,255,.06); border: 1px solid var(--line); border-radius: 18px; padding: 16px; font: inherit; cursor: pointer; transition: transform .15s ease, border-color .15s ease, background .15s ease; }
.option:hover:not(:disabled), .option:focus-visible { transform: translateY(-1px); border-color: rgba(112,225,255,.7); background: rgba(112,225,255,.10); outline: none; }
.option:disabled { cursor: default; opacity: .95; }
.letter { display: grid; place-items: center; width: 38px; height: 38px; border-radius: 12px; font-weight: 900; background: rgba(255,255,255,.10); color: var(--accent); }
.option.correct { border-color: rgba(55,214,122,.8); background: rgba(55,214,122,.16); }
.option.correct .letter { color: #06160d; background: var(--ok); }
.option.wrong { border-color: rgba(255,91,110,.85); background: rgba(255,91,110,.16); }
.option.wrong .letter { color: #210409; background: var(--bad); }
.feedback { margin-top: 18px; padding: 16px 18px; border-radius: 18px; font-weight: 800; }
.feedback.ok { color: #06160d; background: rgba(55,214,122,.92); }
.feedback.bad { color: #fff4f5; background: rgba(255,91,110,.35); border: 1px solid rgba(255,91,110,.55); }
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 20px; }
button.primary, button.secondary { border: 0; border-radius: 999px; padding: 14px 20px; font-weight: 900; font-size: 15px; cursor: pointer; }
button.primary { color: #07111f; background: linear-gradient(90deg, var(--accent), var(--accent-2)); }
button.secondary { color: var(--text); background: rgba(255,255,255,.08); border: 1px solid var(--line); }
.hint { color: var(--muted); margin: 18px 0 0; font-size: 14px; }
.done { text-align: center; }
.done-icon { width: 78px; height: 78px; margin: 0 auto 16px; display: grid; place-items: center; border-radius: 50%; background: var(--ok); color: #06160d; font-size: 42px; font-weight: 1000; }
.hidden { display: none !important; }
@media (max-width: 620px) {
  .shell { width: min(100% - 22px, 980px); padding: 22px 0; }
  .stats { grid-template-columns: 1fr; }
  .option { grid-template-columns: 40px 1fr; padding: 14px; }
  .actions button { width: 100%; }
}