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

:root {
  --bg: #f2ede4;
  --bg-card: #faf6ef;
  --bg-header: #3d5a45;
  --text: #2d2a24;
  --text-light: #6b6559;
  --text-muted: #8a8478;
  --primary: #3d7a5a;
  --primary-hover: #2c5e44;
  --secondary: #7a8c7a;
  --accent: #c4943a;
  --accent-hover: #a87d30;
  --border: #d4cdbc;
  --border-light: #e5dfd0;
  --correct: #4a7a5a;
  --wrong: #b06050;
  --shadow: rgba(45, 42, 36, 0.08);
  --radius: 12px;
}

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

#app {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 16px 32px;
}

header {
  background: var(--bg-header);
  margin: 0 -16px 24px;
  padding: 20px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
}

.header-content h1 {
  color: #e8e0d4;
  font-size: 1.4rem;
  font-weight: 700;
  letter-spacing: -0.3px;
}

.subtitle {
  color: #b8b0a4;
  font-size: 0.85rem;
  margin-top: 2px;
}

.header-actions {
  display: flex;
  gap: 8px;
}

.screen { display: none; }
.screen.active { display: block; }

.btn {
  padding: 10px 20px;
  border: none;
  border-radius: 8px;
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 0.15s ease;
  font-weight: 500;
}

.btn:hover { opacity: 0.9; transform: translateY(-1px); }
.btn:active { transform: translateY(0); }

.btn-primary {
  background: var(--primary);
  color: #f0ece4;
}
.btn-primary:hover { background: var(--primary-hover); }

.btn-secondary {
  background: var(--secondary);
  color: #f0ece4;
}

.btn-accent {
  background: var(--accent);
  color: #2d2a24;
}
.btn-accent:hover { background: var(--accent-hover); }

.btn-calc, .btn-about {
  background: rgba(255,255,255,0.12);
  color: #d4cdbc;
  font-size: 0.85rem;
  padding: 8px 16px;
}
.btn-calc:hover, .btn-about:hover { background: rgba(255,255,255,0.2); }

.btn-large {
  padding: 14px 28px;
  font-size: 1rem;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* Welcome */
.welcome-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 24px;
  text-align: center;
}

.welcome-card h2 {
  font-size: 1.3rem;
  color: var(--text);
  margin-bottom: 8px;
}

.welcome-card p {
  color: var(--text-light);
  font-size: 0.9rem;
  max-width: 600px;
  margin: 0 auto;
}

/* Subjects Grid */
.subjects-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 14px;
  margin-bottom: 28px;
}

.subject-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 20px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.subject-card:hover {
  border-color: var(--primary);
  box-shadow: 0 4px 12px var(--shadow);
  transform: translateY(-2px);
}

.subject-card h3 {
  font-size: 0.95rem;
  color: var(--primary);
  margin-bottom: 6px;
}

.subject-card p {
  font-size: 0.82rem;
  color: var(--text-light);
  line-height: 1.5;
}

.subject-card .question-count {
  display: inline-block;
  margin-top: 10px;
  font-size: 0.78rem;
  color: var(--text-muted);
  background: var(--bg);
  padding: 3px 10px;
  border-radius: 12px;
}

/* Quick Actions */
.quick-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* Quiz Screen */
.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
  flex-wrap: wrap;
  gap: 8px;
}

.quiz-info {
  display: flex;
  gap: 16px;
  align-items: center;
  flex-wrap: wrap;
}

.quiz-subject {
  font-weight: 600;
  color: var(--primary);
  font-size: 0.95rem;
}

.quiz-progress {
  color: var(--text-light);
  font-size: 0.85rem;
}

.quiz-timer {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--text);
  font-variant-numeric: tabular-nums;
}

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

.progress-bar {
  height: 4px;
  background: var(--border-light);
  border-radius: 4px;
  margin-bottom: 20px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--primary);
  border-radius: 4px;
  transition: width 0.3s ease;
}

.question-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 28px;
  margin-bottom: 20px;
}

.question-number {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.question-text {
  font-size: 1.05rem;
  line-height: 1.6;
  margin-bottom: 24px;
  color: var(--text);
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px 16px;
  border: 1px solid var(--border-light);
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.15s ease;
  background: var(--bg);
}

.option-item:hover {
  border-color: var(--primary);
  background: rgba(61, 122, 90, 0.05);
}

.option-item.selected {
  border-color: var(--primary);
  background: rgba(61, 122, 90, 0.1);
}

.option-item.correct {
  border-color: var(--correct);
  background: rgba(74, 122, 90, 0.12);
}

.option-item.wrong {
  border-color: var(--wrong);
  background: rgba(176, 96, 80, 0.1);
}

.option-marker {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: 2px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.78rem;
  font-weight: 600;
  flex-shrink: 0;
  color: var(--text-muted);
}

.option-item.selected .option-marker {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

.option-item.correct .option-marker {
  background: var(--correct);
  border-color: var(--correct);
  color: #fff;
}

.option-item.wrong .option-marker {
  background: var(--wrong);
  border-color: var(--wrong);
  color: #fff;
}

.option-text {
  padding-top: 2px;
  line-height: 1.5;
  color: var(--text);
}

.option-item.selected .option-text { font-weight: 500; }

.quiz-nav {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
}

/* Results */
.results-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 40px 28px;
  text-align: center;
  max-width: 480px;
  margin: 40px auto;
}

.results-card h2 {
  font-size: 1.5rem;
  margin-bottom: 24px;
}

.score-circle {
  width: 140px;
  height: 140px;
  border-radius: 50%;
  border: 4px solid var(--primary);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  margin: 0 auto 24px;
}

.score-number {
  font-size: 2.4rem;
  font-weight: 700;
  color: var(--primary);
}

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

.score-details {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.detail-item {
  font-size: 0.9rem;
  font-weight: 500;
}

.detail-item.correct { color: var(--correct); }
.detail-item.wrong { color: var(--wrong); }
.detail-item.skipped { color: var(--text-muted); }

.score-percentage {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 24px;
}

.results-actions {
  display: flex;
  gap: 10px;
  justify-content: center;
  flex-wrap: wrap;
}

/* Review */
.review-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.review-header h2 {
  font-size: 1.3rem;
}

.review-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.review-item {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 20px;
}

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

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

.review-item.review-skipped {
  border-left: 4px solid var(--text-muted);
}

.review-q {
  font-weight: 500;
  margin-bottom: 12px;
  line-height: 1.5;
}

.review-a {
  font-size: 0.9rem;
  margin-bottom: 4px;
}

.review-a.review-user-correct { color: var(--correct); }
.review-a.review-user-wrong { color: var(--wrong); }
.review-a.review-correct-answer { color: var(--correct); font-weight: 600; }

/* Syllabus */
.syllabus-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.syllabus-header h2 { font-size: 1.3rem; }

.syllabus-content {
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.syllabus-item {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  padding: 20px;
}

.syllabus-item h3 {
  font-size: 1rem;
  color: var(--primary);
  margin-bottom: 6px;
}

.syllabus-item p {
  font-size: 0.85rem;
  color: var(--text-light);
  line-height: 1.5;
  margin-bottom: 8px;
}

.syllabus-item .weight {
  display: inline-block;
  font-size: 0.78rem;
  background: var(--bg);
  color: var(--accent);
  padding: 3px 10px;
  border-radius: 12px;
  font-weight: 600;
}

/* Calculator Modal */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(45, 42, 36, 0.5);
  z-index: 1000;
  align-items: center;
  justify-content: center;
}

.modal.show {
  display: flex;
}

.modal-content {
  background: var(--bg-card);
  border-radius: var(--radius);
  width: 90%;
  max-width: 360px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.15);
}

.calc-content {
  max-width: 320px;
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 20px;
  border-bottom: 1px solid var(--border-light);
}

.modal-header h3 {
  font-size: 1rem;
  color: var(--text);
}

.btn-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-muted);
  padding: 0 4px;
  line-height: 1;
}

.btn-close:hover { color: var(--text); }

.calc-display {
  padding: 20px;
  text-align: right;
  font-size: 1.8rem;
  font-weight: 600;
  color: var(--text);
  background: var(--bg);
  margin: 12px;
  border-radius: 8px;
  min-height: 64px;
  font-variant-numeric: tabular-nums;
  overflow-x: auto;
  word-break: break-all;
}

.calc-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  padding: 12px;
}

.calc-buttons button {
  padding: 16px;
  border: none;
  border-radius: 8px;
  font-size: 1.1rem;
  cursor: pointer;
  background: var(--bg);
  color: var(--text);
  transition: all 0.1s ease;
}

.calc-buttons button:hover {
  background: var(--border-light);
}

.calc-fn {
  color: var(--accent) !important;
  font-weight: 600;
}

.calc-op {
  background: rgba(196, 148, 58, 0.12) !important;
  color: var(--accent) !important;
  font-weight: 600;
}

.calc-eq {
  background: var(--primary) !important;
  color: #f0ece4 !important;
  font-weight: 600;
}

.calc-zero {
  grid-column: span 1;
}

.about-text {
  padding: 20px;
  line-height: 1.7;
  color: var(--text-light);
  font-size: 0.9rem;
}

.about-text p {
  margin-bottom: 10px;
}

.about-text strong {
  color: var(--text);
}

.version {
  margin-top: 16px;
  font-size: 0.82rem;
  color: var(--text-muted);
}

@media (max-width: 640px) {
  header {
    flex-direction: column;
    text-align: center;
  }
  .subjects-grid {
    grid-template-columns: 1fr;
  }
  .quiz-header {
    flex-direction: column;
    align-items: flex-start;
  }
  .quiz-timer {
    align-self: flex-end;
  }
  .score-details {
    gap: 16px;
  }
  .results-card {
    padding: 28px 16px;
  }
}