/* ============================================
   AlphaBook — Dark Theme Stylesheet
   ============================================ */

:root {
  --ab-bg: #0a0e1a;
  --ab-bg-2: #11182a;
  --ab-bg-3: #1a2236;
  --ab-bg-4: #232c44;
  --ab-border: #2a3450;
  --ab-border-light: #3a4565;
  --ab-text: #e6edf3;
  --ab-text-2: #b1bac4;
  --ab-text-3: #7d8590;
  --ab-text-4: #565d68;
  --ab-accent: #22c55e;
  --ab-accent-2: #16a34a;
  --ab-blue: #3b82f6;
  --ab-purple: #a855f7;
  --ab-yellow: #facc15;
  --ab-red: #ef4444;
  --ab-orange: #f97316;
  --ab-cyan: #06b6d4;

  --ab-font-sans: 'Noto Sans KR', -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
  --ab-font-mono: 'JetBrains Mono', 'SF Mono', Menlo, monospace;

  --ab-sidebar-w: 280px;
  --ab-helper-w: 380px;
}

/* base.html이 container를 씌우는데 우리는 풀너비 원함 */
.ab-app {
  position: relative;
  min-height: calc(100vh - 80px);
  margin: -1rem calc(50% - 50vw);  /* container 마진 해제 */
  background: var(--ab-bg);
  color: var(--ab-text);
  font-family: var(--ab-font-sans);
  line-height: 1.7;
}

/* ============================================
   상단바
   ============================================ */
.ab-topbar {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  height: 48px;
  padding: 0 1rem;
  background: var(--ab-bg-2);
  border-bottom: 1px solid var(--ab-border);
}

.ab-menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--ab-text);
  font-size: 1.4rem;
  cursor: pointer;
  padding: 0.25rem 0.5rem;
}

.ab-topbar-title {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  color: var(--ab-text);
  font-weight: 600;
}
.ab-topbar-title:hover { color: var(--ab-accent); }

.ab-logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  background: linear-gradient(135deg, var(--ab-accent), var(--ab-blue));
  color: white;
  border-radius: 6px;
  font-weight: 700;
  font-family: var(--ab-font-mono);
}

.ab-topbar-progress {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8rem;
  color: var(--ab-text-3);
}
.ab-topbar-progress-text { font-family: var(--ab-font-mono); }
.ab-topbar-progress-bar {
  width: 100px;
  height: 4px;
  background: var(--ab-bg-3);
  border-radius: 2px;
  overflow: hidden;
}
.ab-topbar-progress-fill {
  height: 100%;
  background: var(--ab-accent);
  transition: width 0.3s;
}

/* ============================================
   사이드바 (섹션 페이지)
   ============================================ */
.ab-sidebar {
  position: fixed;
  top: 48px;
  left: 0;
  bottom: 0;
  width: var(--ab-sidebar-w);
  background: var(--ab-bg-2);
  border-right: 1px solid var(--ab-border);
  overflow-y: auto;
  z-index: 30;
  font-size: 0.85rem;
}

.ab-sidebar-header {
  padding: 1rem;
  border-bottom: 1px solid var(--ab-border);
  position: sticky;
  top: 0;
  background: var(--ab-bg-2);
}
.ab-sidebar-back {
  color: var(--ab-text-2);
  text-decoration: none;
  font-size: 0.85rem;
}
.ab-sidebar-back:hover { color: var(--ab-accent); }

.ab-sidebar-nav { padding: 0.75rem 0 4rem; }

.ab-sidebar-part {
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--ab-border);
}
.ab-sidebar-part-title {
  padding: 0.5rem 1rem;
  font-weight: 600;
  font-size: 0.8rem;
  color: var(--ab-text-3);
  letter-spacing: 0.02em;
}
.ab-sidebar-part-active .ab-sidebar-part-title {
  color: var(--season-accent, var(--ab-accent));
}

.ab-sidebar-chapter { padding: 0.25rem 0; }
.ab-sidebar-chapter-title {
  padding: 0.4rem 1rem;
  font-size: 0.78rem;
  color: var(--ab-text-2);
  font-weight: 500;
}

.ab-sidebar-sections {
  list-style: none;
  margin: 0;
  padding: 0;
}
.ab-sidebar-sections li {
  display: block;
}
.ab-sidebar-sections a {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 1rem 0.4rem 2rem;
  font-size: 0.82rem;
  color: var(--ab-text-3);
  text-decoration: none;
  border-left: 2px solid transparent;
  transition: all 0.15s;
}
.ab-sidebar-sections a:hover {
  color: var(--ab-text);
  background: var(--ab-bg-3);
}
.ab-sidebar-sec-current a {
  color: var(--season-accent, var(--ab-accent)) !important;
  border-left-color: var(--season-accent, var(--ab-accent));
  background: var(--ab-bg-3);
  font-weight: 500;
}
.ab-sidebar-sec-done a {
  color: var(--ab-text-2);
}
.ab-sidebar-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--ab-text-4);
  flex-shrink: 0;
}
.ab-sidebar-sec-current .ab-sidebar-dot { background: var(--season-accent, var(--ab-accent)); }
.ab-sidebar-check {
  color: var(--ab-accent);
  font-size: 0.75rem;
  flex-shrink: 0;
}

/* ============================================
   메인 콘텐츠 영역
   ============================================ */
.ab-main {
  padding: 0;
  min-height: calc(100vh - 48px - 80px);
}
.ab-app:has(.ab-sidebar) .ab-main {
  margin-left: var(--ab-sidebar-w);
}

/* ============================================
   랜딩 페이지
   ============================================ */
.ab-landing {
  max-width: 980px;
  margin: 0 auto;
  padding: 4rem 1.5rem 6rem;
}

.ab-hero {
  text-align: center;
  margin-bottom: 5rem;
}
.ab-hero-mark {
  font-size: 3rem;
  margin-bottom: 1rem;
  letter-spacing: 0.5rem;
}
.ab-hero-title {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 800;
  line-height: 1.1;
  margin: 0 0 1.5rem;
  letter-spacing: -0.02em;
}
.ab-hero-line1 {
  display: block;
  background: linear-gradient(135deg, var(--ab-accent), var(--ab-cyan));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.ab-hero-line2 {
  display: block;
  background: linear-gradient(135deg, var(--ab-blue), var(--ab-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.ab-hero-subtitle {
  font-size: 1.25rem;
  color: var(--ab-text-2);
  margin-bottom: 2rem;
  line-height: 1.6;
}
.ab-hero-meta {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.75rem;
}
.ab-hero-meta span {
  font-size: 0.85rem;
  color: var(--ab-text-3);
  padding: 0.4rem 0.9rem;
  background: var(--ab-bg-3);
  border: 1px solid var(--ab-border);
  border-radius: 999px;
}

.ab-seasons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-bottom: 5rem;
}
@media (max-width: 720px) {
  .ab-seasons { grid-template-columns: 1fr; }
}

.ab-season-card {
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 16px;
  padding: 2rem 1.75rem;
  position: relative;
  overflow: hidden;
  transition: transform 0.2s, border-color 0.2s;
}
.ab-season-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--season-accent);
}
.ab-season-card:hover {
  transform: translateY(-2px);
  border-color: var(--season-accent);
}
.ab-season-number {
  font-family: var(--ab-font-mono);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--season-accent);
  letter-spacing: 0.1em;
  margin-bottom: 0.75rem;
}
.ab-season-title {
  font-size: 1.6rem;
  margin: 0 0 0.5rem;
  font-weight: 700;
}
.ab-season-subtitle {
  color: var(--ab-text-2);
  font-size: 1rem;
  margin: 0 0 0.75rem;
}
.ab-season-desc {
  color: var(--ab-text-3);
  font-size: 0.9rem;
  line-height: 1.6;
  margin-bottom: 1.5rem;
}
.ab-season-stats {
  display: flex;
  gap: 1.5rem;
  font-size: 0.85rem;
  color: var(--ab-text-3);
  margin-bottom: 1.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--ab-border);
}
.ab-season-stats strong {
  color: var(--ab-text);
  font-family: var(--ab-font-mono);
  font-size: 1.1rem;
  font-weight: 700;
}

.ab-season-cta {
  display: inline-block;
  padding: 0.7rem 1.5rem;
  background: var(--season-accent);
  color: white;
  text-decoration: none;
  border-radius: 8px;
  font-weight: 600;
  transition: opacity 0.15s;
}
.ab-season-cta:hover {
  opacity: 0.9;
  color: white;
}
.ab-season-cta-disabled,
.ab-season-cta-soon {
  background: var(--ab-bg-3);
  color: var(--ab-text-3);
  cursor: not-allowed;
}
.ab-season-toc {
  display: inline-block;
  margin-left: 0.75rem;
  color: var(--ab-text-2);
  text-decoration: none;
  font-size: 0.9rem;
}
.ab-season-toc:hover { color: var(--ab-text); }

.ab-landing-about {
  margin-top: 4rem;
  padding-top: 3rem;
  border-top: 1px solid var(--ab-border);
}
.ab-landing-about h3 {
  font-size: 1.4rem;
  margin-bottom: 1.5rem;
}
.ab-about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}
@media (max-width: 720px) {
  .ab-about-grid { grid-template-columns: 1fr; }
}
.ab-about-grid h4 {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
  font-weight: 600;
}
.ab-about-grid p {
  color: var(--ab-text-2);
  font-size: 0.9rem;
  line-height: 1.6;
}
.ab-landing-foot {
  text-align: center;
  margin-top: 4rem;
  color: var(--ab-text-3);
  font-size: 0.85rem;
}
.ab-landing-foot a { color: var(--ab-accent); text-decoration: none; }

/* ============================================
   시즌 페이지 (목차)
   ============================================ */
.ab-season-page {
  max-width: 900px;
  margin: 0 auto;
  padding: 3rem 1.5rem 6rem;
}
.ab-back-link {
  display: inline-block;
  color: var(--ab-text-3);
  text-decoration: none;
  font-size: 0.9rem;
  margin-bottom: 1rem;
}
.ab-back-link:hover { color: var(--ab-text); }

.ab-season-header { margin-bottom: 3rem; }
.ab-season-num {
  font-family: var(--ab-font-mono);
  font-size: 0.8rem;
  color: var(--season-accent);
  letter-spacing: 0.1em;
  margin-bottom: 0.5rem;
}
.ab-season-header h1 {
  font-size: 2.5rem;
  font-weight: 800;
  margin: 0 0 0.75rem;
  letter-spacing: -0.02em;
}
.ab-season-sub {
  color: var(--ab-text-2);
  font-size: 1.15rem;
  margin: 0 0 0.5rem;
}
.ab-season-desc {
  color: var(--ab-text-3);
  margin-bottom: 1.75rem;
  line-height: 1.7;
}
.ab-start-btn {
  display: inline-block;
  background: var(--season-accent);
  color: white;
  padding: 0.85rem 1.75rem;
  border-radius: 10px;
  text-decoration: none;
  font-weight: 600;
}
.ab-start-btn:hover { color: white; opacity: 0.9; }

.ab-toc-part {
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 12px;
  padding: 1.5rem 1.75rem;
  margin-bottom: 1.5rem;
}
.ab-toc-part-title {
  font-size: 1.3rem;
  margin: 0 0 0.25rem;
}
.ab-toc-part-num {
  display: inline-block;
  font-family: var(--ab-font-mono);
  font-size: 0.7rem;
  background: var(--season-accent);
  color: white;
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
  margin-right: 0.5rem;
  letter-spacing: 0.05em;
  vertical-align: middle;
}
.ab-toc-part-sub {
  color: var(--ab-text-3);
  font-size: 0.9rem;
  margin: 0 0 1rem;
}
.ab-toc-chapter {
  padding: 1rem 0;
  border-top: 1px solid var(--ab-border);
}
.ab-toc-chapter-title {
  font-size: 1.05rem;
  margin: 0 0 0.5rem;
  color: var(--ab-text);
}
.ab-toc-chapter-num {
  color: var(--ab-text-3);
  font-family: var(--ab-font-mono);
  font-size: 0.8rem;
  margin-right: 0.5rem;
}
.ab-toc-chapter-sub {
  color: var(--ab-text-3);
  font-size: 0.85rem;
  margin: 0 0 0.5rem;
}
.ab-toc-sections {
  list-style: none;
  margin: 0;
  padding: 0;
}
.ab-toc-sections li a {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.5rem 0.75rem;
  border-radius: 6px;
  color: var(--ab-text-2);
  text-decoration: none;
  font-size: 0.9rem;
}
.ab-toc-sections li a:hover {
  background: var(--ab-bg-3);
  color: var(--ab-text);
}
.ab-toc-section-done a { color: var(--ab-text-3); }
.ab-toc-section-kind {
  font-family: var(--ab-font-mono);
  font-size: 0.65rem;
  font-weight: 600;
  padding: 0.15rem 0.4rem;
  border-radius: 3px;
  background: var(--ab-bg-3);
  color: var(--ab-text-3);
  letter-spacing: 0.04em;
}
.ab-kind-code { background: rgba(34,197,94,0.15); color: var(--ab-accent); }
.ab-kind-quiz { background: rgba(168,85,247,0.15); color: var(--ab-purple); }
.ab-kind-interactive { background: rgba(6,182,212,0.15); color: var(--ab-cyan); }
.ab-kind-visualization { background: rgba(59,130,246,0.15); color: var(--ab-blue); }
.ab-kind-callout { background: rgba(250,204,21,0.15); color: var(--ab-yellow); }
.ab-check { margin-left: auto; color: var(--ab-accent); }
.ab-toc-empty {
  padding: 0.5rem;
  color: var(--ab-text-4);
  font-size: 0.85rem;
  font-style: italic;
}

/* ============================================
   섹션 페이지 (본문)
   ============================================ */
.ab-section {
  max-width: 780px;
  margin: 0 auto;
  padding: 2.5rem 1.75rem 6rem;
}
.ab-section-header { margin-bottom: 2rem; }
.ab-breadcrumb {
  font-size: 0.82rem;
  color: var(--ab-text-3);
  margin-bottom: 1rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  align-items: center;
}
.ab-breadcrumb a {
  color: var(--ab-text-2);
  text-decoration: none;
}
.ab-breadcrumb a:hover { color: var(--ab-accent); }
.ab-breadcrumb span:not(:has(a)) { color: var(--ab-text-3); }

.ab-section-title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 0 0 0.5rem;
}

.ab-section-body {
  font-size: 1.05rem;
  line-height: 1.85;
  color: var(--ab-text);
}
.ab-section-body p { margin: 0 0 1.25rem; }
.ab-section-body strong { color: var(--ab-text); }
.ab-section-body em { color: var(--ab-text-2); }
.ab-section-body h2 {
  font-size: 1.5rem;
  margin: 2.5rem 0 1rem;
  font-weight: 700;
}
.ab-section-body h3 {
  font-size: 1.2rem;
  margin: 2rem 0 0.75rem;
  font-weight: 600;
}
.ab-section-body ul, .ab-section-body ol {
  padding-left: 1.5rem;
  margin: 0 0 1.5rem;
}
.ab-section-body li { margin: 0.4rem 0; }
.ab-section-body a {
  color: var(--ab-cyan);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}
.ab-section-body code {
  font-family: var(--ab-font-mono);
  font-size: 0.88em;
  padding: 0.15em 0.4em;
  background: var(--ab-bg-3);
  border: 1px solid var(--ab-border);
  border-radius: 4px;
  color: var(--ab-yellow);
}

/* Callout 박스 */
.ab-callout {
  margin: 1.5rem 0;
  padding: 1rem 1.25rem;
  background: var(--ab-bg-2);
  border-left: 3px solid var(--ab-blue);
  border-radius: 6px;
}
.ab-callout-title {
  font-weight: 600;
  margin-bottom: 0.4rem;
  color: var(--ab-text);
}
.ab-callout p:last-child { margin-bottom: 0; }
.ab-callout-tip { border-left-color: var(--ab-accent); }
.ab-callout-warn { border-left-color: var(--ab-orange); }
.ab-callout-next { border-left-color: var(--ab-purple); }

.ab-summary {
  margin: 1.5rem 0;
  padding: 1.5rem;
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 10px;
}
.ab-summary h3 { margin: 0 0 0.75rem; }

/* ============================================
   코드 블록
   ============================================ */
.ab-code-block {
  margin: 1.5rem 0;
  background: #0d1117;
  border: 1px solid var(--ab-border);
  border-radius: 10px;
  overflow: hidden;
}
.ab-code-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 0.85rem;
  background: var(--ab-bg-3);
  border-bottom: 1px solid var(--ab-border);
}
.ab-code-lang {
  font-family: var(--ab-font-mono);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--ab-text-3);
  letter-spacing: 0.05em;
}
.ab-code-actions {
  margin-left: auto;
  display: flex;
  gap: 0.5rem;
}
.ab-btn-ghost, .ab-btn-primary {
  font-size: 0.78rem;
  padding: 0.35rem 0.75rem;
  border: 1px solid var(--ab-border);
  background: var(--ab-bg-3);
  color: var(--ab-text-2);
  border-radius: 5px;
  cursor: pointer;
  font-family: var(--ab-font-sans);
  font-weight: 500;
  transition: all 0.15s;
}
.ab-btn-ghost:hover {
  background: var(--ab-bg-4);
  color: var(--ab-text);
  border-color: var(--ab-border-light);
}
.ab-btn-primary {
  background: var(--ab-accent);
  color: white;
  border-color: var(--ab-accent);
}
.ab-btn-primary:hover { background: var(--ab-accent-2); border-color: var(--ab-accent-2); }
.ab-btn-primary:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.ab-code-editor {
  display: block;
  width: 100%;
  min-height: 180px;
  max-height: 500px;
  border: none;
  resize: vertical;
  padding: 1rem 1.1rem;
  background: #0d1117;
  color: #e6edf3;
  font-family: var(--ab-font-mono);
  font-size: 0.875rem;
  line-height: 1.6;
  tab-size: 4;
  outline: none;
}

.ab-code-output-wrap {
  border-top: 1px solid var(--ab-border);
  background: var(--ab-bg);
}
.ab-code-output-header {
  display: flex;
  justify-content: space-between;
  padding: 0.4rem 0.85rem;
  font-size: 0.72rem;
  color: var(--ab-text-3);
  font-family: var(--ab-font-mono);
  background: var(--ab-bg-2);
  border-bottom: 1px solid var(--ab-border);
  letter-spacing: 0.04em;
}
.ab-code-status.ok { color: var(--ab-accent); }
.ab-code-status.err { color: var(--ab-red); }

.ab-code-output {
  margin: 0;
  padding: 0.9rem 1.1rem;
  font-family: var(--ab-font-mono);
  font-size: 0.84rem;
  line-height: 1.6;
  color: var(--ab-text);
  white-space: pre-wrap;
  word-break: break-word;
  max-height: 400px;
  overflow: auto;
}

.ab-code-solution {
  border-top: 1px solid var(--ab-border);
}
.ab-code-solution summary {
  padding: 0.5rem 0.85rem;
  cursor: pointer;
  font-size: 0.82rem;
  color: var(--ab-text-2);
  font-weight: 500;
  background: var(--ab-bg-2);
}
.ab-code-solution pre {
  margin: 0;
  padding: 1rem 1.1rem;
  background: var(--ab-bg);
  color: var(--ab-text);
  font-family: var(--ab-font-mono);
  font-size: 0.84rem;
  line-height: 1.6;
}

/* ============================================
   퀴즈
   ============================================ */
.ab-quiz {
  margin: 1.5rem 0;
  padding: 1.75rem;
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 12px;
}
.ab-quiz-question {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 1.25rem;
  line-height: 1.6;
}
.ab-quiz-choices {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}
.ab-quiz-choice {
  display: flex;
  align-items: flex-start;
  gap: 0.85rem;
  padding: 0.85rem 1rem;
  background: var(--ab-bg-3);
  border: 1px solid var(--ab-border);
  border-radius: 8px;
  cursor: pointer;
  color: var(--ab-text);
  text-align: left;
  transition: all 0.15s;
  font-family: var(--ab-font-sans);
  font-size: 0.95rem;
  line-height: 1.5;
}
.ab-quiz-choice:hover {
  background: var(--ab-bg-4);
  border-color: var(--ab-border-light);
}
.ab-quiz-choice-letter {
  font-family: var(--ab-font-mono);
  font-weight: 700;
  color: var(--ab-text-3);
  flex-shrink: 0;
  width: 1.5rem;
}
.ab-quiz-choice.correct {
  background: rgba(34,197,94,0.1);
  border-color: var(--ab-accent);
  color: var(--ab-text);
}
.ab-quiz-choice.correct .ab-quiz-choice-letter { color: var(--ab-accent); }
.ab-quiz-choice.wrong {
  background: rgba(239,68,68,0.1);
  border-color: var(--ab-red);
}
.ab-quiz-choice.wrong .ab-quiz-choice-letter { color: var(--ab-red); }
.ab-quiz-choice.disabled { cursor: default; pointer-events: none; }

.ab-quiz-result {
  margin-top: 1.25rem;
  padding: 0.85rem 1rem;
  border-radius: 8px;
  font-weight: 600;
}
.ab-quiz-result.correct {
  background: rgba(34,197,94,0.1);
  color: var(--ab-accent);
  border: 1px solid rgba(34,197,94,0.3);
}
.ab-quiz-result.wrong {
  background: rgba(239,68,68,0.1);
  color: var(--ab-red);
  border: 1px solid rgba(239,68,68,0.3);
}
.ab-quiz-explanation {
  margin-top: 1rem;
  padding: 1rem 1.1rem;
  background: var(--ab-bg-3);
  border-radius: 8px;
  font-size: 0.9rem;
  line-height: 1.7;
  color: var(--ab-text-2);
}
.ab-quiz-explanation strong { display: block; margin-bottom: 0.4rem; color: var(--ab-text); }

/* ============================================
   섹션 네비게이션
   ============================================ */
.ab-section-nav {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 1rem;
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--ab-border);
  align-items: center;
}
@media (max-width: 600px) {
  .ab-section-nav { grid-template-columns: 1fr; }
}
.ab-nav-prev, .ab-nav-next {
  display: flex;
  flex-direction: column;
  padding: 0.85rem 1rem;
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 8px;
  text-decoration: none;
  color: var(--ab-text);
  transition: all 0.15s;
}
.ab-nav-next { text-align: right; }
.ab-nav-prev:hover, .ab-nav-next:hover {
  border-color: var(--season-accent, var(--ab-accent));
  color: var(--ab-text);
  transform: translateY(-1px);
}
.ab-nav-label {
  font-size: 0.75rem;
  color: var(--ab-text-3);
  margin-bottom: 0.2rem;
}
.ab-nav-title { font-size: 0.92rem; font-weight: 500; }

.ab-btn-mark-done {
  background: var(--season-accent, var(--ab-accent));
  color: white;
  border: none;
  padding: 0.7rem 1.3rem;
  border-radius: 8px;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--ab-font-sans);
  white-space: nowrap;
}
.ab-btn-mark-done:hover { opacity: 0.9; }
.ab-btn-marked {
  background: var(--ab-bg-3);
  color: var(--ab-accent);
  border: 1px solid var(--ab-accent);
}

/* ============================================
   AI 헬퍼 (플로팅)
   ============================================ */
.ab-helper-fab {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--ab-accent), var(--ab-cyan));
  color: white;
  border: none;
  cursor: pointer;
  box-shadow: 0 6px 20px rgba(0,0,0,0.35);
  z-index: 60;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.15s;
}
.ab-helper-fab:hover { transform: scale(1.05); }
.ab-helper-fab.hidden { display: none; }

.ab-helper-panel {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  width: var(--ab-helper-w);
  max-width: calc(100vw - 3rem);
  height: 540px;
  max-height: calc(100vh - 5rem);
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 14px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.5);
  z-index: 70;
  display: none;
  flex-direction: column;
  overflow: hidden;
}
.ab-helper-panel.open { display: flex; }

.ab-helper-header {
  display: flex;
  align-items: center;
  padding: 0.85rem 1rem;
  background: var(--ab-bg-3);
  border-bottom: 1px solid var(--ab-border);
}
.ab-helper-title {
  font-weight: 600;
  font-size: 0.95rem;
}
.ab-helper-sub {
  font-size: 0.75rem;
  color: var(--ab-text-3);
  margin-top: 0.15rem;
}
.ab-helper-close {
  margin-left: auto;
  background: none;
  border: none;
  color: var(--ab-text-3);
  font-size: 1.6rem;
  line-height: 1;
  cursor: pointer;
  padding: 0 0.4rem;
}
.ab-helper-close:hover { color: var(--ab-text); }

.ab-helper-log {
  flex: 1;
  overflow-y: auto;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}
.ab-helper-msg {
  padding: 0.7rem 0.9rem;
  border-radius: 10px;
  font-size: 0.88rem;
  line-height: 1.6;
  max-width: 88%;
  white-space: pre-wrap;
  word-wrap: break-word;
}
.ab-helper-msg-user {
  align-self: flex-end;
  background: var(--ab-accent);
  color: white;
}
.ab-helper-msg-ai {
  align-self: flex-start;
  background: var(--ab-bg-3);
  color: var(--ab-text);
  border: 1px solid var(--ab-border);
}
.ab-helper-msg-error {
  align-self: stretch;
  background: rgba(239,68,68,0.1);
  color: var(--ab-red);
  border: 1px solid rgba(239,68,68,0.3);
  font-size: 0.82rem;
}
.ab-helper-msg-loading {
  align-self: flex-start;
  background: var(--ab-bg-3);
  color: var(--ab-text-3);
  border: 1px solid var(--ab-border);
  font-style: italic;
}
.ab-helper-msg code {
  font-family: var(--ab-font-mono);
  font-size: 0.85em;
  background: rgba(0,0,0,0.25);
  padding: 0.1em 0.3em;
  border-radius: 3px;
}

.ab-helper-form {
  display: flex;
  gap: 0.5rem;
  padding: 0.75rem;
  background: var(--ab-bg-3);
  border-top: 1px solid var(--ab-border);
}
.ab-helper-form textarea {
  flex: 1;
  resize: none;
  padding: 0.55rem 0.7rem;
  background: var(--ab-bg);
  color: var(--ab-text);
  border: 1px solid var(--ab-border);
  border-radius: 8px;
  font-family: var(--ab-font-sans);
  font-size: 0.88rem;
  outline: none;
}
.ab-helper-form textarea:focus { border-color: var(--ab-accent); }
.ab-helper-send {
  padding: 0 1rem;
  background: var(--ab-accent);
  color: white;
  border: none;
  border-radius: 8px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  font-family: var(--ab-font-sans);
  font-size: 0.85rem;
}
.ab-helper-send:hover { background: var(--ab-accent-2); }
.ab-helper-send:disabled { opacity: 0.5; cursor: not-allowed; }

/* ============================================
   시각화 (바둑판 등)
   ============================================ */
.ab-viz {
  margin: 1.5rem 0;
  padding: 1rem;
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 10px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}
.ab-viz-loading {
  color: var(--ab-text-3);
  font-style: italic;
}

/* 5x5 바둑판 SVG */
.ab-goban {
  background: #d4a04a;
  border-radius: 6px;
  box-shadow: 0 4px 16px rgba(0,0,0,0.3);
}
.ab-goban-turn {
  font-family: var(--ab-font-mono);
  font-size: 0.85rem;
  color: var(--ab-text-2);
  margin-top: 0.5rem;
}
.ab-goban-controls {
  display: flex;
  gap: 0.5rem;
}

/* ============================================
   모바일
   ============================================ */
@media (max-width: 900px) {
  .ab-menu-btn { display: block; }
  .ab-sidebar {
    transform: translateX(-100%);
    transition: transform 0.25s;
  }
  .ab-sidebar.open { transform: translateX(0); }
  .ab-app:has(.ab-sidebar) .ab-main { margin-left: 0; }
  .ab-section { padding: 1.5rem 1rem 5rem; }
  .ab-section-title { font-size: 1.5rem; }
  .ab-helper-panel {
    right: 0.5rem;
    bottom: 0.5rem;
    height: 460px;
  }
  .ab-helper-fab {
    right: 1rem;
    bottom: 1rem;
  }
}
/* ============================================
   AlphaBook CSS — Chapter 2 추가 분
   기존 alphabook.css 파일 끝에 이어붙이세요.
   ============================================ */

/* 보드 위 타이틀 */
.ab-goban-title {
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--ab-text);
  margin-bottom: 0.5rem;
  text-align: center;
}

/* 활로 범례 */
.ab-goban-legend {
  display: flex;
  gap: 1rem;
  font-size: 0.75rem;
  color: var(--ab-text-3);
  margin-top: 0.4rem;
  flex-wrap: wrap;
  justify-content: center;
}
.ab-leg-dot {
  display: inline-block;
  width: 10px;
  height: 10px;
  border-radius: 50%;
  vertical-align: middle;
  margin-right: 0.25rem;
}
.ab-leg-liberty {
  background: #ef4444;
}
.ab-leg-atari {
  background: transparent;
  border: 2px solid #ef4444;
}

/* atari 링 (단수 강조) 펄스 애니메이션 */
.ab-goban-atari-ring {
  animation: ab-atari-pulse 1.4s ease-in-out infinite;
}
@keyframes ab-atari-pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.35; }
}

/* ============================================
   알파북 미니 푸터 (글로벌 푸터 대체) + body 다크화
   ============================================ */

/* 알파북 페이지일 때 body 자체를 다크 배경으로 (콘텐츠 짧을 때 빈 공간 메우기) */
body:has(.ab-app) {
  background: var(--ab-bg) !important;
}

/* main.container의 max-width/padding 제거 (알파북 풀너비) */
body:has(.ab-app) > main.container {
  max-width: none !important;
  padding-left: 0 !important;
  padding-right: 0 !important;
  background: var(--ab-bg);
}

.ab-mini-footer {
  background: var(--ab-bg-2);
  border-top: 1px solid var(--ab-border);
  padding: 1.25rem 1rem;
  color: var(--ab-text-3);
  font-size: 0.78rem;
  margin-top: 0;
}

.ab-mini-foot-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.4rem 0.65rem;
  align-items: center;
}

.ab-mini-foot-brand {
  color: var(--ab-text-2);
}
.ab-mini-foot-brand strong {
  color: var(--ab-text);
}

.ab-mini-foot-inner a {
  color: var(--ab-text-2);
  text-decoration: none;
  transition: color 0.15s;
}
.ab-mini-foot-inner a:hover {
  color: var(--ab-accent);
}

.ab-mini-foot-sep {
  color: var(--ab-text-4);
}

@media (max-width: 600px) {
  .ab-mini-footer { padding: 1rem 0.75rem; font-size: 0.72rem; }
  .ab-mini-foot-inner { gap: 0.3rem 0.5rem; }
}

/* ============================================
   학습 몰입을 위해 알파북 페이지에서 광고 숨기기
   (siteradar 방식 차용)
   ============================================ */
body:has(.ab-app) ins.adsbygoogle,
body:has(.ab-app) .adsbygoogle,
body:has(.ab-app) [class*="adsbygoogle"],
body:has(.ab-app) iframe[src*="google"],
body:has(.ab-app) iframe[src*="doubleclick"],
body:has(.ab-app) iframe[src*="googlesyndication"],
body:has(.ab-app) iframe[src*="googleadservices"],
body:has(.ab-app) div[id*="google_ads"],
body:has(.ab-app) div[class*="ad-container"],
body:has(.ab-app) div[class*="ad_container"],
body:has(.ab-app) div[id^="div-gpt-ad"],
body:has(.ab-app) ins[data-ad-client],
body:has(.ab-app) ins[data-ad-slot] {
  display: none !important;
}

/* ============================================
   Compare 레이아웃 (Ch 3 §3 Before/After 등)
   body_html 안 인라인 viz 두 개 나란히 표시
   ============================================ */
.ab-compare-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  margin: 1.5rem 0;
}
@media (max-width: 720px) {
  .ab-compare-grid { grid-template-columns: 1fr; }
}
.ab-compare-side {
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 10px;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
}
.ab-compare-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--ab-text);
  text-align: center;
}

/* ============================================
   영역(집) 시각화 범례 — Ch 5
   ============================================ */
.ab-leg-box {
  display: inline-block;
  width: 12px;
  height: 12px;
  border-radius: 2px;
  vertical-align: middle;
  margin-right: 0.25rem;
}
.ab-leg-territory-b { background: #0a0a0a; opacity: 0.6; }
.ab-leg-territory-w { background: #f5f5f5; opacity: 0.7; border: 1px solid #888; }
.ab-leg-territory-n { background: #888; opacity: 0.4; }

/* ============================================
   Tree Visualization (게임 트리, Minimax)
   ============================================ */
.ab-tree-svg {
  background: var(--ab-bg-2);
  border: 1px solid var(--ab-border);
  border-radius: 8px;
  display: block;
  margin: 0 auto;
}
.ab-tree-title {
  text-align: center;
  font-size: 0.9rem;
  color: var(--ab-text);
  margin-bottom: 0.5rem;
  font-weight: 600;
}
.ab-tree-legend {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.5rem 1rem;
  margin-top: 0.5rem;
  font-size: 0.78rem;
  color: var(--ab-text-3);
}
.ab-tree-leg-mark {
  font-weight: bold;
  font-size: 1rem;
  vertical-align: middle;
  margin-right: 0.15rem;
}
.ab-tree-leg-max { color: #22c55e; }
.ab-tree-leg-min { color: #ef4444; }
.ab-tree-leg-leaf { color: #3b82f6; }

/* ============================================
   Tic-Tac-Toe Visualization (틱택토)
   ============================================ */
.ab-ttt-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
  margin: 1rem 0;
}
.ab-ttt-title {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--ab-text);
}
.ab-ttt-result {
  font-size: 1rem;
  font-weight: 700;
  color: var(--ab-accent);
  margin-top: 0.25rem;
}