*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: #f8f9fa; color: #111827; line-height: 1.7; -webkit-font-smoothing: antialiased;
}
.container { max-width: 840px; margin: 0 auto; padding: 0 24px; }
a { color: #a06b3a; text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3 { font-family: 'Cinzel', serif; color: #111827; }
h1 { font-size: 2rem; margin-bottom: 16px; line-height: 1.3; }
h2 { font-size: 1.4rem; margin: 40px 0 16px; border-bottom: 1px solid #e5e7eb; padding-bottom: 8px; }
h3 { font-size: 1.1rem; margin: 24px 0 8px; }
.nav { border-bottom: 1px solid #e5e7eb; padding: 16px 0; margin-bottom: 32px; background: #ffffff; }
.nav .container { display: flex; justify-content: space-between; align-items: center; }
.nav-logo { font-family: 'Cinzel', serif; font-size: 1.3rem; font-weight: 700; color: #a06b3a; }
.nav-link { color: #4b5563; font-size: 0.9rem; }
.nav-link:hover { color: #a06b3a; }
.stats-bar { display: flex; flex-wrap: wrap; gap: 16px; padding: 16px 20px; background: #ffffff; border: 1px solid #d1d5db; border-radius: 8px; margin: 20px 0 32px; font-size: 0.9rem; color: #4b5563; }
.stat-item { display: flex; align-items: center; gap: 6px; }
.stat-value { color: #111827; font-weight: 600; }
.intro { font-size: 1.05rem; color: #374151; margin-bottom: 8px; }
.question-card { background: #ffffff; border: 1.5px solid #e5e7eb; border-radius: 14px; padding: 24px; margin-bottom: 20px; box-shadow: 0 1px 4px rgba(0,0,0,0.06); }
.question-header { display: flex; align-items: center; gap: 10px; margin-bottom: 14px; font-size: 0.85rem; color: #4b5563; }
.difficulty-badge { padding: 2px 10px; border-radius: 12px; font-size: 0.8rem; font-weight: 600; }
.question-text { margin-bottom: 16px; line-height: 1.7; }
.choices { display: flex; flex-direction: column; gap: 8px; }
.choice-btn { display: flex; align-items: flex-start; gap: 12px; padding: 14px 16px; border-radius: 10px; background: #ffffff; border: 1.5px solid #e5e7eb; cursor: pointer; text-align: left; width: 100%; font-family: 'DM Sans', sans-serif; font-size: 0.95rem; color: #111827; line-height: 1.6; transition: all 0.2s; box-shadow: 0 1px 3px rgba(0,0,0,0.06); }
.choice-btn:hover { background: #f5f5f5; border-color: #a06b3a; }
.choice-btn.selected { background: rgba(160,107,58,0.1); border-color: #a06b3a; }
.choice-btn.selected .choice-letter-box { background: #a06b3a; color: #fff; border-color: #a06b3a; }
.choice-btn.correct { background: rgba(4,120,87,0.12); border-color: #047857; color: #047857; }
.choice-btn.correct .choice-letter-box { background: #047857; color: #fff; border-color: #047857; }
.choice-btn.correct:hover { background: rgba(4,120,87,0.12); border-color: #047857; }
.choice-btn.dimmed { opacity: 0.5; cursor: default; }
.choice-btn.dimmed:hover { background: #ffffff; border-color: #e5e7eb; }
.choice-letter-box { width: 28px; height: 28px; min-width: 28px; border-radius: 7px; background: #f3f4f6; border: 1.5px solid #e5e7eb; display: flex; align-items: center; justify-content: center; font-size: 12px; font-weight: 700; color: #4b5563; font-family: 'JetBrains Mono', monospace; flex-shrink: 0; transition: all 0.2s; }
.choice-text { flex: 1; min-width: 0; }
.show-answer-btn { display: block; width: 100%; padding: 14px 20px; margin-top: 16px; border-radius: 10px; background: #a06b3a; border: none; color: #fff; font-size: 0.95rem; font-weight: 700; cursor: pointer; font-family: 'DM Sans', sans-serif; transition: opacity 0.2s; }
.show-answer-btn:hover { opacity: 0.9; }
.answer-section { display: none; margin-top: 16px; }
.feedback-banner { display: flex; align-items: center; gap: 10px; padding: 14px 18px; border-radius: 12px; background: rgba(4,120,87,0.12); border: 1px solid #047857; margin-bottom: 16px; }
.feedback-icon { font-size: 20px; }
.feedback-label { font-size: 14px; font-weight: 600; color: #047857; }
.solution-box { padding: 20px 24px; border-radius: 12px; background: #faf8f5; border-left: 4px solid #a06b3a; border-top: 1px solid #e5e7eb; border-right: 1px solid #e5e7eb; border-bottom: 1px solid #e5e7eb; font-size: 0.95rem; line-height: 1.7; }
.solution-label { font-size: 12px; color: #a06b3a; text-transform: uppercase; letter-spacing: 0.08em; margin-bottom: 10px; font-weight: 700; }
@keyframes seoFadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }
.cta-section { text-align: center; margin: 48px 0; }
.cta-button { display: inline-block; padding: 14px 32px; background: #a06b3a; color: #ffffff; font-weight: 700; font-size: 1.05rem; border-radius: 8px; text-decoration: none; transition: opacity 0.2s; }
.cta-button:hover { opacity: 0.9; text-decoration: none; }
.topic-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 16px; margin: 20px 0; }
.topic-card { background: #ffffff; border: 1px solid #d1d5db; border-radius: 8px; padding: 20px; transition: border-color 0.2s; }
.topic-card:hover { border-color: #a06b3a; }
.topic-card h3 { margin: 0 0 8px; font-size: 1rem; }
.topic-card .topic-count { color: #4b5563; font-size: 0.85rem; }
.related-topics { display: flex; flex-wrap: wrap; gap: 8px; margin: 16px 0; }
.related-tag { padding: 6px 14px; background: #ffffff; border: 1px solid #d1d5db; border-radius: 20px; font-size: 0.85rem; color: #374151; transition: border-color 0.2s; }
.related-tag:hover { border-color: #a06b3a; text-decoration: none; }
.footer { border-top: 1px solid #e5e7eb; margin-top: 48px; padding: 32px 0; color: #4b5563; font-size: 0.85rem; }
.footer-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 24px; margin-bottom: 24px; }
.footer h4 { color: #374151; font-family: 'Cinzel', serif; margin-bottom: 10px; font-size: 0.95rem; }
.footer ul { list-style: none; padding: 0; }
.footer li { margin-bottom: 6px; }
.footer a { color: #4b5563; }
.footer a:hover { color: #a06b3a; }
.footer-disclaimer { margin-bottom: 20px; padding: 16px 20px; background: #f9fafb; border: 1px solid #e5e7eb; border-radius: 8px; font-size: 0.75rem; line-height: 1.6; color: #6b7280; }
.footer-disclaimer p { margin: 0 0 8px; }
.footer-disclaimer p:last-child { margin-bottom: 0; }
.footer-bottom { text-align: center; padding-top: 16px; border-top: 1px solid #e5e7eb; }
.about-section { background: #ffffff; border: 1px solid #d1d5db; border-radius: 8px; padding: 24px; margin: 32px 0; }
.provider-section { margin: 32px 0; }
.provider-label { font-family: 'Cinzel', serif; font-size: 0.9rem; color: #4b5563; text-transform: uppercase; letter-spacing: 1px; margin-bottom: 12px; }
.exam-card { background: #ffffff; border: 1px solid #d1d5db; border-radius: 8px; padding: 20px; transition: border-color 0.2s; display: block; }
.exam-card:hover { border-color: #a06b3a; text-decoration: none; }
.exam-card h3 { color: #111827; margin: 0 0 6px; }
.exam-card .exam-meta { color: #4b5563; font-size: 0.85rem; }
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; margin: 20px 0 32px; }
.feature-card { background: #ffffff; border: 1px solid #e5e7eb; border-radius: 10px; padding: 18px; display: flex; gap: 14px; align-items: flex-start; }
.feature-icon { width: 38px; height: 38px; min-width: 38px; border-radius: 10px; display: flex; align-items: center; justify-content: center; font-size: 16px; font-weight: 700; }
.feature-title { font-size: 0.9rem; font-weight: 700; color: #111827; margin-bottom: 2px; }
.feature-desc { font-size: 0.8rem; color: #6b7280; line-height: 1.5; }
.lesson-preview { background: #faf8f5; border: 1px solid #e5ddd3; border-radius: 12px; padding: 28px; margin: 20px 0; }
.lesson-preview-badge { display: inline-flex; align-items: center; gap: 6px; padding: 4px 12px; background: rgba(160,107,58,0.12); border-radius: 20px; font-size: 0.78rem; font-weight: 600; color: #a06b3a; margin-bottom: 12px; }
.lesson-preview h3 { font-family: 'Cinzel', serif; font-size: 1.1rem; margin: 0 0 4px; color: #111827; }
.lesson-preview .lesson-topic { font-size: 0.85rem; color: #6b7280; margin-bottom: 14px; }
.lesson-preview .lesson-hook { font-size: 0.95rem; color: #374151; line-height: 1.8; border-left: 3px solid #a06b3a; padding-left: 16px; margin: 0 0 18px; }
.lesson-preview .lesson-hook p { margin: 0 0 8px; }
.lesson-preview .lesson-hook p:last-child { margin-bottom: 0; }
.lesson-preview .lesson-cta { display: inline-block; padding: 10px 20px; background: #a06b3a; color: #ffffff; font-weight: 600; font-size: 0.9rem; border-radius: 8px; text-decoration: none; transition: opacity 0.2s; }
.lesson-preview .lesson-cta:hover { opacity: 0.9; text-decoration: none; }
.exam-card .exam-tags { display: flex; gap: 6px; margin-top: 8px; flex-wrap: wrap; }
.exam-tag { display: inline-block; padding: 2px 8px; border-radius: 10px; font-size: 0.7rem; font-weight: 600; }
@media (max-width: 900px) { .feature-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 600px) { h1 { font-size: 1.5rem; } .stats-bar { flex-direction: column; gap: 8px; } .topic-grid { grid-template-columns: 1fr; } .footer-grid { grid-template-columns: 1fr 1fr; } .feature-grid { grid-template-columns: 1fr; } }
.katex { font-size: 1em; }
.katex-display { margin: 12px 0; overflow-x: auto; }