:root {
  --color-correct: #198754;
  --color-correct-bg: #d1e7dd;
  --color-wrong: #dc3545;
  --color-wrong-bg: #f8d7da;
  --color-current: #0d6efd;
  --color-current-bg: #e7f1ff;
  --sticky-height: auto;
}

body {
  background: #f0f2f5;
  min-height: 100vh;
}

.app-shell {
  min-height: 100vh;
}

.exam-card {
  cursor: pointer;
  transition: box-shadow 0.15s ease, border-color 0.15s ease;
  border: 2px solid transparent;
}

.exam-card:hover {
  box-shadow: 0 0.25rem 0.75rem rgba(0, 0, 0, 0.08);
}

.exam-card.selected {
  border-color: var(--color-current);
  background: var(--color-current-bg);
}

.exam-sticky {
  position: sticky;
  top: 0;
  z-index: 1020;
  background: #fff;
  border-bottom: 1px solid #dee2e6;
}

.timer-display {
  font-family: "SF Mono", "Menlo", "Consolas", monospace;
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-current);
  letter-spacing: 0.05em;
}

.timer-display.timer-warning {
  color: var(--color-wrong);
}

.nav-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  max-height: 9rem;
  overflow-y: auto;
  padding: 0.25rem;
  background: #f8f9fa;
  border-radius: 0.5rem;
  border: 1px solid #e9ecef;
}

.nav-cell {
  width: 2.1rem;
  height: 2.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid #dee2e6;
  border-radius: 0.35rem;
  background: #fff;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  user-select: none;
  transition: background 0.1s, border-color 0.1s, color 0.1s;
}

.nav-cell:hover {
  border-color: var(--color-current);
}

.nav-cell.visited {
  background: #f8f9fa;
}

.nav-cell.current {
  background: var(--color-current-bg);
  border-color: var(--color-current);
  outline: 2px solid var(--color-current);
  outline-offset: 1px;
}

.nav-cell.correct {
  background: var(--color-correct);
  border-color: var(--color-correct);
  color: #fff;
}

.nav-cell.wrong {
  background: var(--color-wrong);
  border-color: var(--color-wrong);
  color: #fff;
}

.nav-cell.reviewed {
  background: #6c757d;
  border-color: #6c757d;
  color: #fff;
}

.question-card {
  border: none;
  border-radius: 0.75rem;
}

.question-text {
  font-size: 1.05rem;
  line-height: 1.6;
  white-space: pre-wrap;
}

.option-btn {
  display: block;
  width: 100%;
  text-align: left;
  padding: 0.85rem 1rem;
  margin-bottom: 0.5rem;
  border: 2px solid #dee2e6;
  border-radius: 0.6rem;
  background: #fff;
  transition: border-color 0.15s, background 0.15s;
}

.option-btn:hover:not(:disabled) {
  border-color: #adb5bd;
  background: #f8f9fa;
}

.option-btn .option-letter {
  font-weight: 700;
  margin-right: 0.5rem;
}

.option-btn.correct {
  background: var(--color-correct-bg);
  border-color: var(--color-correct);
}

.option-btn.wrong {
  background: var(--color-wrong-bg);
  border-color: var(--color-wrong);
}

.option-btn.selected-pending {
  border-color: var(--color-current);
  background: var(--color-current-bg);
}

.explanation-panel {
  background: #f8f9fa;
  border-left: 4px solid var(--color-correct);
  border-radius: 0.5rem;
  padding: 1rem 1.25rem;
}

.explanation-text {
  white-space: pre-wrap;
  line-height: 1.55;
  font-size: 0.95rem;
}

.option-breakdown-item {
  border-radius: 0.5rem;
  padding: 0.85rem 1rem;
  margin-bottom: 0.65rem;
  border: 1px solid #dee2e6;
  background: #fff;
}

.option-breakdown-item.breakdown-correct {
  border-color: var(--color-correct);
  background: var(--color-correct-bg);
}

.option-breakdown-item.breakdown-incorrect {
  border-color: #dee2e6;
  background: #fff;
}

.option-breakdown-header {
  font-size: 0.95rem;
  margin-bottom: 0.35rem;
}

.option-breakdown-explanation {
  white-space: pre-wrap;
  font-size: 0.9rem;
  line-height: 1.5;
  color: #333;
  margin-bottom: 0.35rem;
}

.option-breakdown-status {
  font-size: 0.85rem;
  font-weight: 700;
}

.option-breakdown-status.correct {
  color: var(--color-correct);
}

.option-breakdown-status.incorrect {
  color: var(--color-wrong);
}

.feedback-wrong {
  color: var(--color-wrong);
  font-weight: 600;
}

.feedback-correct {
  color: var(--color-correct);
  font-weight: 600;
}

.result-stat .stat-value {
  font-size: 2rem;
  font-weight: 700;
}

.review-item {
  border-radius: 0.75rem;
}

.review-item.correct-item {
  border-left: 4px solid var(--color-correct);
}

.review-item.wrong-item {
  border-left: 4px solid var(--color-wrong);
}

.review-item.neutral-item {
  border-left: 4px solid #6c757d;
}

@media (max-width: 576px) {
  .timer-display {
    font-size: 1.4rem;
  }

  .nav-cell {
    width: 1.9rem;
    height: 1.9rem;
    font-size: 0.72rem;
  }
}