:root {
  color-scheme: light;
  --indigo-600: #4f46e5;
  --indigo-500: #6366f1;
  --indigo-100: #e0e7ff;
  --slate-900: #0f172a;
  --slate-800: #1e293b;
  --slate-700: #334155;
  --slate-600: #475569;
  --slate-500: #64748b;
  --slate-200: #e2e8f0;
  --slate-100: #f1f5f9;
  --emerald-500: #10b981;
  --emerald-100: #d1fae5;
  --rose-500: #f43f5e;
  --rose-100: #ffe4e6;
  --white: #ffffff;
  --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --radius: 12px;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: "Inter", system-ui, -apple-system, sans-serif;
  color: var(--slate-900);
  background: var(--white);
  min-height: 100vh;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  padding: 2rem 0 0;
}

a {
  color: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

button {
  font-family: inherit;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 1rem;
}

.quiz-section {
  background: transparent;
  padding: 0;
}

.quiz-header {
  text-align: center;
  margin-bottom: 3rem;
  margin-top: 2rem;
  color: var(--slate-900);
}

.quiz-header h1 {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--indigo-600);
}

.quiz-header p {
  font-size: 1.1rem;
  color: var(--slate-600);
}

.score {
  background: var(--white);
  border-radius: var(--radius);
  padding: 1.5rem;
  text-align: center;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--indigo-600);
  box-shadow: var(--shadow-lg);
  margin-bottom: 2rem;
  display: none;
}

.quiz-grid {
  display: grid;
  gap: 2.5rem;
  margin-bottom: 3rem;
}

.card {
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 24px -4px rgba(0, 0, 0, 0.12), 0 8px 16px -4px rgba(0, 0, 0, 0.08);
}

.question-text {
  background: var(--indigo-600);
  color: var(--white);
  padding: 1.25rem 1.5rem;
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.5;
}

.question-text small {
  display: block;
  margin-top: 0.5rem;
  font-weight: 400;
  font-size: 0.875rem;
  opacity: 0.9;
}

.options {
  padding: 1.5rem;
}

.options li {
  margin-bottom: 0.75rem;
}

.options li:last-child {
  margin-bottom: 0;
}

.option {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  background: var(--slate-100);
  border: 2px solid transparent;
  border-radius: 8px;
  padding: 0.875rem 1rem;
  transition: all 0.2s ease;
  cursor: pointer;
  font-weight: 500;
}

.option:hover {
  border-color: var(--indigo-500);
  background: var(--indigo-100);
}

.option input[type="checkbox"],
.option input[type="radio"] {
  width: 20px;
  height: 20px;
  cursor: pointer;
  accent-color: var(--indigo-600);
}

.option.correct {
  background: var(--emerald-100);
  border-color: var(--emerald-500);
  color: var(--slate-900);
}

.option.wrong {
  background: var(--rose-100);
  border-color: var(--rose-500);
  color: var(--slate-900);
}

.input-wrapper {
  display: flex;
  align-items: center;
  padding: 1.5rem;
  gap: 0.75rem;
}

.input-ans {
  width: 120px;
  padding: 0.875rem 1rem;
  border-radius: 8px;
  border: 2px solid var(--slate-200);
  font-size: 1rem;
  font-weight: 600;
  transition: all 0.2s ease;
}

.input-ans:focus {
  outline: none;
  border-color: var(--indigo-500);
  box-shadow: 0 0 0 3px var(--indigo-100);
}

.unit-label {
  font-weight: 600;
  color: var(--slate-600);
  font-size: 1rem;
}

.input-ans.correct {
  border-color: var(--emerald-500);
  background: var(--emerald-100);
}

.input-ans.wrong {
  border-color: var(--rose-500);
  background: var(--rose-100);
}

.rationale {
  display: none;
  background: linear-gradient(135deg, var(--indigo-100) 0%, #e0e7ff 100%);
  padding: 1rem 1.25rem;
  margin: 0 1.5rem 1.5rem;
  border-radius: 8px;
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--slate-800);
  font-weight: 500;
}
.btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  background: var(--indigo-600);
  color: var(--white);
  padding: 1rem 2.5rem;
  border-radius: 10px;
  font-weight: 700;
  font-size: 1.1rem;
  border: none;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: var(--shadow-lg);
  width: 100%;
  max-width: 300px;
  margin: 0 auto;
}

.btn:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: 0 12px 24px -4px rgba(79, 70, 229, 0.3);
  background: var(--indigo-500);
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.footer {
  text-align: center;
  padding: 2rem 0;
  background: var(--slate-900);
  color: var(--white);
  font-size: 0.9rem;
  margin-top: 4rem;
}

@media (max-width: 768px) {
  body {
    padding: 1rem 0 0;
  }

  .quiz-header h1 {
    font-size: 1.75rem;
  }

  .quiz-header p {
    font-size: 1rem;
  }

  .card {
    font-size: 0.95rem;
  }

  .question-text {
    padding: 1rem;
  }

  .options {
    padding: 1rem;
  }

  .option {
    padding: 0.75rem 0.875rem;
  }
}