:root {
  --bg: #f4f7fb;
  --card: #ffffff;
  --text: #172033;
  --muted: #687386;
  --line: #dce3ef;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --success: #15803d;
  --danger: #b91c1c;
  --soft-blue: #eaf1ff;
  --soft-green: #eaf8ef;
  --soft-red: #fdecec;
  --shadow: 0 18px 45px rgba(23, 32, 51, 0.08);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: Inter, Segoe UI, Roboto, Arial, sans-serif;
  background: radial-gradient(circle at top left, #dbeafe, transparent 35%), var(--bg);
  color: var(--text);
  min-height: 100vh;
}

.app-shell {
  width: min(980px, calc(100% - 32px));
  margin: 32px auto;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 22px;
  box-shadow: var(--shadow);
  padding: 32px;
}

.hidden { display: none; }

.eyebrow {
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.78rem;
  font-weight: 800;
  margin-bottom: 10px;
}

h1, h2 {
  margin: 0 0 14px;
  line-height: 1.2;
}

p {
  color: var(--muted);
  line-height: 1.6;
}

.info-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
  margin: 24px 0;
}

.info-grid div {
  background: #f8fafc;
  border: 1px solid var(--line);
  padding: 14px;
  border-radius: 14px;
}

button {
  border: 0;
  border-radius: 12px;
  padding: 12px 18px;
  font-weight: 800;
  cursor: pointer;
  transition: transform 0.12s ease, background 0.12s ease, opacity 0.12s ease;
}

button:hover { transform: translateY(-1px); }

button:disabled {
  cursor: not-allowed;
  opacity: 0.55;
  transform: none;
}

.primary-btn {
  color: #fff;
  background: var(--primary);
}

.primary-btn:hover { background: var(--primary-dark); }

.secondary-btn {
  color: var(--text);
  background: #eef2f7;
}

.test-header,
.review-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 24px;
  margin-bottom: 24px;
}

.progress-wrap {
  min-width: 220px;
  color: var(--muted);
  font-size: 0.9rem;
}

.progress-bar {
  height: 10px;
  background: #e8edf5;
  border-radius: 99px;
  margin-top: 8px;
  overflow: hidden;
}

#progressFill {
  height: 100%;
  width: 0%;
  background: var(--primary);
  border-radius: 99px;
}

.choice {
  display: block;
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 15px;
  margin-bottom: 12px;
  cursor: pointer;
  background: #fff;
}

.choice:hover { background: #f8fafc; }

.choice input { margin-right: 10px; }

.choice.selected {
  border-color: var(--primary);
  background: var(--soft-blue);
}

.nav-row {
  display: flex;
  gap: 12px;
  justify-content: flex-end;
  margin-top: 24px;
  flex-wrap: wrap;
}

.score-box {
  display: inline-flex;
  align-items: baseline;
  gap: 8px;
  padding: 20px 26px;
  background: var(--soft-blue);
  border: 1px solid #bfd2ff;
  border-radius: 18px;
  font-size: 2.4rem;
  font-weight: 900;
  margin: 10px 0;
}

.score-box span {
  font-size: 1rem;
  color: var(--muted);
}

.review-item {
  border: 1px solid var(--line);
  border-radius: 18px;
  padding: 18px;
  margin-bottom: 16px;
  background: #fff;
}

.review-item.correct {
  border-color: #bbf7d0;
  background: var(--soft-green);
}

.review-item.wrong {
  border-color: #fecaca;
  background: var(--soft-red);
}

.review-meta {
  font-weight: 900;
  margin-bottom: 8px;
}

.answer-line { margin: 8px 0; }

.explanation {
  color: var(--muted);
  line-height: 1.55;
  margin-top: 10px;
}

.tag {
  display: inline-block;
  padding: 4px 9px;
  border-radius: 99px;
  font-size: 0.78rem;
  font-weight: 800;
  margin-left: 8px;
}

.correct-tag {
  background: #dcfce7;
  color: var(--success);
}

.wrong-tag {
  background: #fee2e2;
  color: var(--danger);
}

@media (max-width: 720px) {
  .card { padding: 22px; }

  .info-grid {
    grid-template-columns: 1fr;
  }

  .test-header,
  .review-header {
    display: block;
  }

  .progress-wrap {
    min-width: 100%;
    margin-top: 18px;
  }

  .nav-row { justify-content: stretch; }

  button { flex: 1; }
}