:root {
  --swiss: #d52b1e;
  --swiss-dark: #b21f15;
  --correct: #1b873f;
  --correct-bg: #e7f6ec;
  --wrong: #c0392b;
  --wrong-bg: #fcebe9;
  --bg: #eef0f3;
  --card: #ffffff;
  --ink: #1c2024;
  --muted: #6b7280;
  --border: #e2e5ea;
  --shadow: 0 1px 2px rgba(16, 24, 40, 0.04), 0 6px 20px rgba(16, 24, 40, 0.07);
  --radius: 14px;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

/* ---------- Header ---------- */
#stats-bar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  gap: 0.75rem 1rem;
  align-items: center;
  flex-wrap: wrap;
  padding: 0.7rem 1.1rem;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(1.4) blur(8px);
  border-bottom: 1px solid var(--border);
}
.brand {
  font-weight: 700;
  letter-spacing: -0.01em;
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
}
.brand-cross {
  display: inline-grid;
  place-items: center;
  width: 1.45rem;
  height: 1.45rem;
  border-radius: 6px;
  background: var(--swiss);
  color: #fff;
  font-size: 0.95rem;
  line-height: 1;
}
.stats-group { display: flex; gap: 0.4rem; flex-wrap: wrap; }
.stat {
  font-weight: 600;
  font-size: 0.82rem;
  color: var(--ink);
  background: #f1f3f6;
  border: 1px solid var(--border);
  padding: 0.25rem 0.6rem;
  border-radius: 999px;
  font-variant-numeric: tabular-nums;
}
.filter {
  margin-left: auto;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.85rem;
  color: var(--muted);
}
#topic-filter {
  font: inherit;
  color: var(--ink);
  padding: 0.35rem 0.5rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fff;
  cursor: pointer;
}
#reset-btn {
  font: inherit;
  font-size: 0.82rem;
  color: var(--muted);
  background: transparent;
  border: 1px solid var(--border);
  padding: 0.35rem 0.7rem;
  border-radius: 8px;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s, background 0.15s;
}
#reset-btn:hover { color: var(--swiss); border-color: var(--swiss); background: #fff5f4; }

/* ---------- Layout ---------- */
main {
  max-width: 760px;
  margin: 1.75rem auto 3rem;
  padding: 0 1rem;
  display: grid;
  gap: 1.25rem;
}

/* ---------- Question card ---------- */
#question-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.6rem 1.75rem 1.75rem;
  box-shadow: var(--shadow);
}
.meta {
  color: var(--swiss);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  margin: 0 0 0.6rem;
}
#question-text {
  font-size: 1.4rem;
  line-height: 1.3;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0 0 1.25rem;
}
#question-image {
  max-width: 100%;
  height: auto;
  border-radius: 10px;
  border: 1px solid var(--border);
  margin-bottom: 1.25rem;
}

/* ---------- Answers ---------- */
#answers { list-style: none; margin: 0; padding: 0; display: grid; gap: 0.6rem; }
.answer-btn {
  position: relative;
  width: 100%;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-align: left;
  padding: 0.85rem 1rem;
  border: 1.5px solid var(--border);
  border-radius: 11px;
  background: #fff;
  color: var(--ink);
  font: inherit;
  font-size: 1rem;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s, transform 0.06s, box-shadow 0.15s;
}
.answer-btn:hover:not(:disabled) {
  border-color: #c7ccd4;
  background: #fafbfc;
  box-shadow: var(--shadow);
}
.answer-btn:active:not(:disabled) { transform: translateY(1px); }
.answer-btn:focus-visible {
  outline: none;
  border-color: var(--swiss);
  box-shadow: 0 0 0 3px rgba(213, 43, 30, 0.22);
}
.answer-btn:disabled { cursor: default; opacity: 1; }
.answer-btn img {
  max-width: 200px;
  height: auto;
  display: block;
  border-radius: 6px;
}
.answer-btn .key {
  flex: 0 0 auto;
  display: inline-grid;
  place-items: center;
  width: 1.7rem;
  height: 1.7rem;
  border-radius: 7px;
  background: #f1f3f6;
  border: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.85rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}
.answer-btn.correct {
  border-color: var(--correct);
  background: var(--correct-bg);
}
.answer-btn.correct .key { background: var(--correct); border-color: var(--correct); color: #fff; }
.answer-btn.wrong {
  border-color: var(--wrong);
  background: var(--wrong-bg);
}
.answer-btn.wrong .key { background: var(--wrong); border-color: var(--wrong); color: #fff; }
/* ✓ / ✗ markers after answering */
.answer-btn.correct::after,
.answer-btn.wrong::after {
  margin-left: auto;
  font-weight: 700;
  font-size: 1.1rem;
}
.answer-btn.correct::after { content: "✓"; color: var(--correct); }
.answer-btn.wrong::after { content: "✗"; color: var(--wrong); }

/* ---------- Explanation + Next ---------- */
.explanation {
  margin: 1.1rem 0 0;
  background: #f3f6ff;
  border-left: 3px solid var(--swiss);
  border-radius: 8px;
  padding: 0.8rem 1rem;
  font-size: 0.95rem;
}
#next-btn {
  margin-top: 1.25rem;
  padding: 0.7rem 1.6rem;
  border: none;
  border-radius: 10px;
  background: var(--swiss);
  color: #fff;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, transform 0.06s, box-shadow 0.15s;
  box-shadow: 0 2px 8px rgba(213, 43, 30, 0.28);
}
#next-btn:hover { background: var(--swiss-dark); }
#next-btn:active { transform: translateY(1px); }
#next-btn:focus-visible { outline: none; box-shadow: 0 0 0 3px rgba(213, 43, 30, 0.3); }

/* ---------- Stats panel ---------- */
#topic-stats {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1.5rem 1.5rem;
  box-shadow: var(--shadow);
}
#topic-stats h2 {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
  margin: 0 0 0.6rem;
}
#topic-stats h2:not(:first-child) { margin-top: 1.4rem; }
#topic-stats ul { list-style: none; margin: 0; padding: 0; }
#topic-stats-list li {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--border);
  font-size: 0.92rem;
  font-variant-numeric: tabular-nums;
}
#topic-stats-list li:last-child { border-bottom: none; }
#box-stats-list { display: flex; flex-wrap: wrap; gap: 0.5rem; }
#box-stats-list li {
  background: #f1f3f6;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.4rem 0.7rem;
  font-size: 0.85rem;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

/* ---------- Responsive ---------- */
@media (max-width: 560px) {
  .filter { margin-left: 0; width: 100%; }
  #question-card { padding: 1.25rem 1.1rem 1.4rem; }
  #question-text { font-size: 1.2rem; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}