* {
  box-sizing: border-box;
}

:root {
  --bg: #0b1220;
  --panel: #121a2b;
  --panel-soft: #18233a;
  --text: #e8eefc;
  --muted: #9eb1d4;
  --accent: #60a5fa;
  --border: #2a3a5a;
}

body {
  margin: 0;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  background: radial-gradient(circle at top, #14213d 0%, var(--bg) 48%);
  color: var(--text);
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(8px);
  background: rgba(11, 18, 32, 0.84);
  border-bottom: 1px solid var(--border);
  padding: 18px 24px;
}

.topbar-inner {
  max-width: 1250px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
}

.topbar-brand {
  color: var(--text);
  text-decoration: none;
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.3px;
}

.topbar-nav {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.topbar-nav a {
  color: var(--muted);
  text-decoration: none;
  padding: 8px 10px;
  border-radius: 999px;
  transition: background 0.2s ease, color 0.2s ease;
}

.topbar-nav a:hover {
  color: var(--text);
  background: rgba(96, 165, 250, 0.12);
}

.topbar h1 {
  margin: 0;
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.3px;
}

.layout {
  max-width: 1250px;
  margin: 0 auto;
  padding: 24px;
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 24px;
  align-items: start;
}

.sidebar {
  position: sticky;
  top: 88px;
  border: 1px solid var(--border);
  border-radius: 16px;
  background: linear-gradient(145deg, rgba(96, 165, 250, 0.1), rgba(18, 26, 43, 0.96));
  padding: 18px;
}

.sidebar h2 {
  margin: 0 0 14px;
  font-size: 1rem;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.8px;
}

.sidebar nav {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.sidebar a {
  color: var(--text);
  text-decoration: none;
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid transparent;
  background: rgba(255, 255, 255, 0.02);
}

.sidebar a:hover {
  border-color: #3e5b91;
  background: rgba(96, 165, 250, 0.12);
}

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

.accordion-item {
  border: 1px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  background: linear-gradient(165deg, rgba(24, 35, 58, 0.96), rgba(18, 26, 43, 0.98));
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.22);
}

.accordion-header {
  width: 100%;
  border: 0;
  background: transparent;
  color: var(--text);
  text-align: left;
  padding: 16px 18px;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.chapter-title {
  flex: 1;
}

.chapter-weight {
  display: none;
}

.accordion-header::after {
  content: "+";
  font-size: 1.2rem;
  color: var(--accent);
  transition: transform 0.2s ease;
}

.accordion-header:hover {
  background: rgba(96, 165, 250, 0.08);
}

.accordion-item.open .accordion-header::after {
  content: "−";
  transform: scale(1.12);
}

.accordion-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.28s ease;
}

.accordion-item.open .accordion-content {
  border-top: 1px solid var(--border);
}

.accordion-content ul {
  margin: 0;
  padding: 14px 20px 18px 34px;
}

.accordion-content li {
  margin: 8px 0;
  line-height: 1.45;
  color: #dce5f8;
}

.topic-row {
  display: inline;
}

.topic-text {
  display: inline;
}

.resource-chip {
  display: inline-block;
  border: 1px solid #3d5582;
  border-radius: 0;
  background: rgba(96, 165, 250, 0.12);
  color: #cfe4ff;
  font-size: 0.64rem;
  letter-spacing: 0.3px;
  padding: 2px 7px;
  text-transform: uppercase;
  text-decoration: none;
  vertical-align: middle;
}

.resource-chip:hover {
  color: #dbeafe;
  border-color: #69a8f5;
  background: rgba(96, 165, 250, 0.2);
}

.resource-card {
  margin-top: 10px;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: rgba(96, 165, 250, 0.08);
  padding: 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.resource-card-copy {
  margin: 0;
  color: #dce5f8;
  line-height: 1.6;
}

.resource-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.resource-list-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 12px;
  border: 1px solid rgba(96, 165, 250, 0.22);
  border-radius: 12px;
  background: rgba(11, 18, 32, 0.42);
}

.resource-title {
  color: var(--text);
  font-size: 0.95rem;
  font-weight: 600;
  line-height: 1.45;
}

.resource-link-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 36px;
  padding: 8px 12px;
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-decoration: none;
  transition: transform 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}

.resource-link-btn:hover {
  color: #dbeafe;
  border-color: #69a8f5;
  background: rgba(96, 165, 250, 0.2);
  transform: translateY(-1px);
}

.accordion-content li ul {
  padding-top: 7px;
}

.contribution-section {
  margin-top: 8px;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: linear-gradient(165deg, rgba(24, 35, 58, 0.96), rgba(18, 26, 43, 0.98));
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.22);
  padding: 18px;
}

.contribution-section h2 {
  margin: 0 0 10px;
  font-size: 1.08rem;
}

.contribution-section p {
  margin: 0 0 10px;
  color: #dce5f8;
}

.contribution-section ol {
  margin: 0;
  padding-left: 20px;
}

.contribution-section li {
  margin: 7px 0;
  color: #dce5f8;
}

.exam-info {
  margin-top: 8px;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: linear-gradient(165deg, rgba(24, 35, 58, 0.96), rgba(18, 26, 43, 0.98));
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.22);
  padding: 18px;
}

.exam-info h2 {
  margin: 0 0 14px;
  font-size: 1.08rem;
}

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

.info-card {
  border: 1px solid #3a4e77;
  border-radius: 12px;
  background: rgba(96, 165, 250, 0.08);
  padding: 14px;
}

.info-card h3 {
  margin: 0 0 8px;
  font-size: 0.95rem;
  color: var(--muted);
}

.info-card p {
  margin: 0;
  color: var(--text);
}

.site-footer {
  margin-top: 20px;
  border-top: 1px solid var(--border);
  background: rgba(10, 16, 28, 0.92);
  padding: 18px 24px 26px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  flex-wrap: nowrap;
}

.site-footer p {
  margin: 0;
  color: var(--muted);
}

.social-links {
  display: flex;
  align-items: center;
  gap: 10px;
}

.social-links a {
  width: 40px;
  height: 40px;
  border-radius: 10px;
  border: 1px solid #3a4e77;
  background: rgba(96, 165, 250, 0.08);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s ease;
}

.social-links a:hover {
  transform: translateY(-2px);
  border-color: #69a8f5;
  background: rgba(96, 165, 250, 0.2);
}

.social-links svg {
  width: 19px;
  height: 19px;
  fill: #e8eefc;
}

@media (max-width: 980px) {
  .layout {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
  }

  .site-footer {
    padding: 16px;
    gap: 10px;
  }

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

@media (max-width: 420px) {
  .site-footer p {
    font-size: 0.92rem;
  }

  .social-links {
    gap: 8px;
  }

  .social-links a {
    width: 36px;
    height: 36px;
  }
}