:root {
  color-scheme: light dark;
  --bg: #eef2f8;
  --surface: #ffffff;
  --text: #0f172a;
  --muted: #536179;
  --border: #d7e0ec;
  --accent: #1d4ed8;
  --on-accent: #ffffff;
  --header: #13306b;
  --ok: #166534;
  --ok-bg: #dcfce7;
  --bad: #991b1b;
  --bad-bg: #fee2e2;
  --code-bg: #0b1220;
  --code-text: #e2e8f0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1220;
    --surface: #131c2e;
    --text: #e5e9f0;
    --muted: #94a3b8;
    --border: #24324a;
    --accent: #93c5fd;
    --on-accent: #0b1a33;
    --header: #101b33;
    --ok: #bbf7d0;
    --ok-bg: #14532d;
    --bad: #fecaca;
    --bad-bg: #7f1d1d;
    --code-bg: #050a14;
  }
}
[hidden] { display: none !important; }
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text); font-size: 1.0625rem; line-height: 1.55; }
.top { padding: 14px 16px; background: var(--header); color: #fff; }
.top h1 { max-width: 728px; margin: 0 auto; font-size: 1.15rem; }
main { max-width: 760px; margin: 0 auto; padding: 8px 16px 48px; }
h2 { margin: 22px 0 8px; font-size: 1.05rem; }
.note { padding: 10px 12px; border: 1px dashed var(--border); border-radius: 10px; color: var(--muted); font-size: 0.92rem; }
.hint { color: var(--muted); font-size: 0.9rem; }
.card { padding: 12px 14px; background: var(--surface); border: 1px solid var(--border); border-radius: 14px; overflow-wrap: anywhere; }
.card p { margin: 4px 0; }
.buttons { display: flex; flex-wrap: wrap; gap: 8px; }
button {
  min-height: 44px;
  padding: 8px 14px;
  font: inherit;
  color: var(--on-accent);
  background: var(--accent);
  border: none;
  border-radius: 10px;
  cursor: pointer;
}
button:disabled { opacity: 0.5; cursor: default; }
button.danger { background: var(--bad-bg); color: var(--bad); }
.progress { padding: 10px 12px; background: var(--surface); border: 1px solid var(--border); border-radius: 10px; font-size: 0.92rem; }
.result { margin: 12px 0; padding: 12px 14px; background: var(--surface); border: 1px solid var(--border); border-radius: 14px; }
.result h3 { margin: 0 0 6px; font-size: 1rem; }
.pass { color: var(--ok); background: var(--ok-bg); padding: 0 8px; border-radius: 999px; font-size: 0.85rem; font-weight: 600; }
.fail { color: var(--bad); background: var(--bad-bg); padding: 0 8px; border-radius: 999px; font-size: 0.85rem; font-weight: 600; }
.answer { margin: 6px 0 12px; padding: 8px 10px; background: var(--bg); border-radius: 8px; white-space: pre-wrap; font-size: 0.92rem; overflow-wrap: anywhere; }
.summary { padding: 10px 12px; background: var(--code-bg); color: var(--code-text); border-radius: 10px; font-size: 0.82rem; white-space: pre-wrap; overflow-wrap: anywhere; }
.error { color: var(--bad); }