/* study.plynte.com - Master Stylesheet */
:root {
  --bg-primary: #0b0f19;
  --bg-secondary: #0f172a;
  --bg-surface: #1e293b;
  --bg-surface-hover: #334155;
  --border-color: #334155;
  --border-subtle: #1e293b;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --accent: #38bdf8;
  --accent-hover: #0284c7;
  --accent-glow: rgba(56, 189, 248, 0.15);
  --code-bg: #030712;
  --code-border: #1f2937;
  --success: #10b981;
  --success-bg: rgba(16, 185, 129, 0.12);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.12);
  --danger: #ef4444;
  --danger-bg: rgba(239, 68, 68, 0.12);
  --info: #0ea5e9;
  --info-bg: rgba(14, 165, 233, 0.12);
  --content-font-size: 17px;
  --header-height: 60px;
  --sidebar-width: 320px;
  --toc-width: 240px;
  --font-sans: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', Menlo, Monaco, Consolas, monospace;
}

[data-theme="light"] {
  --bg-primary: #f8fafc;
  --bg-secondary: #f1f5f9;
  --bg-surface: #ffffff;
  --bg-surface-hover: #f1f5f9;
  --border-color: #e2e8f0;
  --border-subtle: #cbd5e1;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  --accent: #0284c7;
  --accent-hover: #0369a1;
  --accent-glow: rgba(2, 132, 199, 0.12);
  --code-bg: #f8fafc;
  --code-border: #e2e8f0;
  --success: #059669;
  --success-bg: rgba(5, 150, 105, 0.1);
  --warning: #d97706;
  --warning-bg: rgba(217, 119, 6, 0.1);
  --danger: #dc2626;
  --danger-bg: rgba(220, 38, 38, 0.1);
  --info: #0284c7;
  --info-bg: rgba(2, 132, 199, 0.1);
}

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

html {
  font-family: var(--font-sans);
  font-size: var(--content-font-size);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 1.5rem);
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  line-height: 1.65;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.15s ease;
}
a:hover {
  color: var(--accent-hover);
  text-decoration: underline;
}

/* ---------------- TOP BAR ---------------- */
.top-bar {
  position: sticky;
  top: 0;
  height: var(--header-height);
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.25rem;
  z-index: 100;
  backdrop-filter: blur(8px);
}

.top-bar-left {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.btn-hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  gap: 4px;
  width: 36px;
  height: 36px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  cursor: pointer;
  padding: 6px;
}
.btn-hamburger .bar {
  width: 18px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: all 0.2s;
}

.site-brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text-primary);
  text-decoration: none !important;
}
.brand-logo {
  font-size: 1.2rem;
}

.top-quick-links {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}
.quick-link {
  font-size: 0.88rem;
  color: var(--text-secondary);
  font-weight: 500;
  transition: color 0.15s;
}
.quick-link:hover {
  color: var(--accent);
  text-decoration: none;
}

.top-bar-right {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.btn-search-trigger {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 0.4rem 0.75rem;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 0.85rem;
  transition: all 0.2s;
}
.btn-search-trigger:hover {
  border-color: var(--accent);
  color: var(--text-primary);
}
.kbd-shortcut {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 0.1rem 0.35rem;
  font-size: 0.7rem;
  font-family: var(--font-mono);
}

.btn-sync-trigger {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 0.4rem 0.65rem;
  color: var(--text-secondary);
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 500;
  transition: all 0.2s;
}
.btn-sync-trigger:hover {
  border-color: var(--accent);
  color: var(--text-primary);
  background: var(--bg-surface-hover);
}
.sync-label {
  font-weight: 600;
}

.font-size-controls {
  display: flex;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  overflow: hidden;
}
.btn-font-size {
  background: var(--bg-surface);
  border: none;
  padding: 0.35rem 0.6rem;
  color: var(--text-primary);
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 600;
}
.btn-font-size:hover {
  background: var(--bg-surface-hover);
}

.btn-theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 6px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  cursor: pointer;
}
[data-theme="dark"] .btn-theme-toggle .moon-icon { display: none; }
[data-theme="dark"] .btn-theme-toggle .sun-icon { display: block; color: #fbbf24; }
[data-theme="light"] .btn-theme-toggle .sun-icon { display: none; }
[data-theme="light"] .btn-theme-toggle .moon-icon { display: block; color: #0284c7; }

.btn-author {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 0.4rem 0.65rem;
  text-decoration: none !important;
}
.btn-author:hover {
  color: var(--text-primary);
  border-color: var(--accent);
}

/* ---------------- LAYOUT GRID ---------------- */
.layout-container {
  display: flex;
  flex: 1;
  width: 100%;
  position: relative;
}

/* ---------------- LEFT SIDEBAR ---------------- */
.site-sidebar {
  width: var(--sidebar-width);
  height: calc(100vh - var(--header-height));
  position: sticky;
  top: var(--header-height);
  background: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  overflow-y: auto;
  flex-shrink: 0;
  padding: 1.25rem 1rem;
}

.sidebar-progress-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 0.85rem;
  margin-bottom: 1.25rem;
}
.progress-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}
.progress-score {
  color: var(--accent);
  font-family: var(--font-mono);
}
.progress-track {
  width: 100%;
  height: 8px;
  background: var(--bg-primary);
  border-radius: 4px;
  overflow: hidden;
  margin-bottom: 0.5rem;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--success));
  border-radius: 4px;
  transition: width 0.3s ease;
}
.progress-card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.5rem;
  font-size: 0.75rem;
  color: var(--text-muted);
}
.progress-card-actions {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.btn-sidebar-sync {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  color: var(--accent);
  padding: 0.2rem 0.5rem;
  font-size: 0.72rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
}
.btn-sidebar-sync:hover {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.btn-reset-progress {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  text-decoration: underline;
  font-size: 0.72rem;
}
.btn-reset-progress:hover {
  color: var(--danger);
}

.nav-module-group {
  margin-bottom: 1rem;
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  overflow: hidden;
}
.nav-module-summary {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.65rem 0.75rem;
  background: var(--bg-surface);
  cursor: pointer;
  font-weight: 700;
  font-size: 0.88rem;
  user-select: none;
}
.nav-module-summary::-webkit-details-marker { display: none; }
.nav-module-summary .group-count {
  margin-left: auto;
  font-size: 0.75rem;
  background: var(--bg-secondary);
  padding: 0.1rem 0.4rem;
  border-radius: 10px;
  color: var(--text-muted);
}

.nav-subgroup {
  margin: 0.35rem 0.5rem;
}
.nav-subgroup-summary {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-secondary);
  padding: 0.35rem 0.5rem;
  cursor: pointer;
  border-radius: 4px;
}
.nav-subgroup-summary:hover {
  background: var(--bg-surface-hover);
  color: var(--text-primary);
}

.sidebar-nav-list {
  list-style: none;
  padding: 0.25rem 0.5rem;
}
.sidebar-nav-item {
  margin: 2px 0;
}
.sidebar-nav-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 0.6rem;
  border-radius: 6px;
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.35;
  transition: all 0.15s;
}
.sidebar-nav-link:hover {
  background: var(--bg-surface-hover);
  color: var(--text-primary);
  text-decoration: none;
}
.sidebar-nav-link.active {
  background: var(--accent-glow);
  color: var(--accent);
  font-weight: 600;
  border-left: 3px solid var(--accent);
}
.lesson-check-badge {
  width: 14px;
  height: 14px;
  border: 1px solid var(--border-color);
  border-radius: 3px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 10px;
  flex-shrink: 0;
  transition: all 0.2s;
}
.lesson-check-badge.checked {
  background: var(--success);
  border-color: var(--success);
  color: #fff;
}
.lesson-check-badge.checked::after {
  content: '✓';
}

/* ---------------- MAIN CONTENT ---------------- */
.main-content {
  flex: 1;
  min-width: 0;
  padding: 2rem 2.5rem;
  display: flex;
  justify-content: center;
}
.content-wrapper {
  width: 100%;
  max-width: 860px;
}

.breadcrumb-nav {
  margin-bottom: 1.5rem;
  font-size: 0.85rem;
}
.breadcrumb-list {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
}
.breadcrumb-item + .breadcrumb-item::before {
  content: '/';
  color: var(--text-muted);
  margin-right: 0.5rem;
}
.breadcrumb-item.active span {
  color: var(--text-secondary);
}

.lesson-completion-banner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.85rem 1.25rem;
  margin-bottom: 2rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  gap: 1rem;
}
.completion-info {
  display: flex;
  flex-direction: column;
}
.completion-badge {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--accent);
  letter-spacing: 0.05em;
}
.completion-desc {
  font-size: 0.82rem;
  color: var(--text-muted);
}
.btn-complete-lesson {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 1rem;
  font-size: 0.85rem;
  font-weight: 600;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background: var(--bg-secondary);
  color: var(--text-primary);
  cursor: pointer;
  transition: all 0.2s;
  flex-shrink: 0;
}
.btn-complete-lesson:hover {
  border-color: var(--accent);
  color: var(--accent);
}
.btn-complete-lesson.completed {
  background: var(--success-bg);
  border-color: var(--success);
  color: var(--success);
}

/* ---------------- ARTICLE TYPOGRAPHY ---------------- */
.article-body h1, .article-body h2, .article-body h3, .article-body h4, .article-body h5, .article-body h6 {
  color: var(--text-primary);
  font-weight: 700;
  line-height: 1.3;
  margin-top: 2rem;
  margin-bottom: 1rem;
  position: relative;
}
.article-body h1 {
  font-size: 2.2rem;
  margin-top: 0.5rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border-color);
}
.article-body h2 {
  font-size: 1.55rem;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border-subtle);
}
.article-body h3 { font-size: 1.25rem; }
.article-body h4 { font-size: 1.1rem; }

.header-anchor {
  opacity: 0;
  margin-left: 0.5rem;
  color: var(--text-muted);
  text-decoration: none !important;
  font-weight: 400;
  transition: opacity 0.15s;
}
h1:hover .header-anchor, h2:hover .header-anchor, h3:hover .header-anchor, h4:hover .header-anchor {
  opacity: 1;
}

.article-body p {
  margin-bottom: 1.25rem;
  color: var(--text-primary);
}

.article-body strong {
  font-weight: 600;
  color: var(--text-primary);
}

.article-body code:not([class*="language-"]) {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 0.15rem 0.35rem;
  font-family: var(--font-mono);
  font-size: 0.88em;
  color: #f43f5e;
}
[data-theme="light"] .article-body code:not([class*="language-"]) {
  color: #be123c;
}

.article-body ul.content-list, .article-body ol.content-list {
  margin-bottom: 1.25rem;
  padding-left: 1.5rem;
}
.article-body li {
  margin-bottom: 0.45rem;
}
.task-item {
  list-style: none;
  margin-left: -1.2rem;
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
}
.task-item input[type="checkbox"] {
  accent-color: var(--accent);
}

.divider {
  border: 0;
  height: 1px;
  background: var(--border-color);
  margin: 2.5rem 0;
}

/* ---------------- CODE BLOCKS & COPY ---------------- */
.code-block-wrapper {
  margin: 1.5rem 0;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 8px;
  overflow: hidden;
}
.code-block-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.4rem 0.85rem;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-color);
}
.code-lang-badge {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: 0.05em;
}
.diagram-badge {
  color: #34d399;
}
.btn-copy-code {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 0.25rem 0.55rem;
  font-size: 0.75rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.15s;
}
.btn-copy-code:hover {
  border-color: var(--accent);
  color: var(--accent);
}
.btn-copy-code.copied {
  border-color: var(--success);
  color: var(--success);
}

.code-block-wrapper pre {
  padding: 1rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.55;
  color: #e2e8f0;
}
[data-theme="light"] .code-block-wrapper pre {
  color: #0f172a;
}

/* ---------------- SYNTAX HIGHLIGHTING TOKENS ---------------- */
.code-block-wrapper .hl-cm   { color: #64748b; font-style: italic; }
.code-block-wrapper .hl-kw   { color: #c084fc; font-weight: 600; }
.code-block-wrapper .hl-type { color: #38bdf8; }
.code-block-wrapper .hl-fn   { color: #60a5fa; }
.code-block-wrapper .hl-macro{ color: #2dd4bf; font-weight: 600; }
.code-block-wrapper .hl-attr { color: #f59e0b; }
.code-block-wrapper .hl-life { color: #fb7185; font-style: italic; }
.code-block-wrapper .hl-str  { color: #a3e635; }
.code-block-wrapper .hl-num  { color: #fb923c; }
.code-block-wrapper .hl-bool { color: #f472b6; font-weight: 600; }
.code-block-wrapper .hl-op   { color: #94a3b8; }

[data-theme="light"] .code-block-wrapper .hl-cm   { color: #64748b; font-style: italic; }
[data-theme="light"] .code-block-wrapper .hl-kw   { color: #7e22ce; font-weight: 600; }
[data-theme="light"] .code-block-wrapper .hl-type { color: #0369a1; }
[data-theme="light"] .code-block-wrapper .hl-fn   { color: #1d4ed8; }
[data-theme="light"] .code-block-wrapper .hl-macro{ color: #0f766e; font-weight: 600; }
[data-theme="light"] .code-block-wrapper .hl-attr { color: #b45309; }
[data-theme="light"] .code-block-wrapper .hl-life { color: #be123c; font-style: italic; }
[data-theme="light"] .code-block-wrapper .hl-str  { color: #15803d; }
[data-theme="light"] .code-block-wrapper .hl-num  { color: #c2410c; }
[data-theme="light"] .code-block-wrapper .hl-bool { color: #be185d; font-weight: 600; }
[data-theme="light"] .code-block-wrapper .hl-op   { color: #475569; }

/* ---------------- RESPONSIVE TABLES ---------------- */
.table-wrapper {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 1.75rem 0;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  background: var(--bg-surface);
}
.table-wrapper table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}
.table-wrapper th {
  background: var(--bg-secondary);
  padding: 0.75rem 1rem;
  font-weight: 600;
  color: var(--text-primary);
  border-bottom: 2px solid var(--border-color);
  white-space: nowrap;
}
.table-wrapper td {
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border-color);
  color: var(--text-secondary);
}
.table-wrapper tr:last-child td {
  border-bottom: none;
}
.table-wrapper tr:hover td {
  background: var(--bg-surface-hover);
}

/* ---------------- DETAILS ACCORDIONS ---------------- */
details.study-accordion {
  margin: 1.5rem 0;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  background: var(--bg-surface);
  overflow: hidden;
  transition: border-color 0.2s, box-shadow 0.2s;
}
details.study-accordion[open] {
  border-color: var(--accent);
  box-shadow: 0 4px 14px var(--accent-glow);
}
details.study-accordion summary {
  padding: 0.85rem 1.25rem;
  font-weight: 600;
  cursor: pointer;
  user-select: none;
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.65rem;
  color: var(--text-primary);
  background: var(--bg-surface);
}
details.study-accordion summary::-webkit-details-marker { display: none; }
details.study-accordion summary::before {
  content: '▶';
  font-size: 0.7rem;
  color: var(--accent);
  transition: transform 0.2s ease;
  flex-shrink: 0;
}
details.study-accordion[open] summary::before {
  transform: rotate(90deg);
}
details.study-accordion summary:hover {
  background: var(--bg-surface-hover);
}
details.study-accordion > *:not(summary) {
  padding: 0 1.25rem 1rem 1.25rem;
}

/* ---------------- GITHUB ALERTS ---------------- */
.alert {
  margin: 1.75rem 0;
  padding: 1.1rem 1.25rem;
  border-radius: 8px;
  border-left: 4px solid var(--border-color);
  background: var(--bg-surface);
}
.alert-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 700;
  margin-bottom: 0.65rem;
  font-size: 0.95rem;
}
.alert-body p:last-child {
  margin-bottom: 0;
}
.alert-note { border-left-color: var(--info); background: var(--info-bg); }
.alert-tip { border-left-color: var(--success); background: var(--success-bg); }
.alert-important { border-left-color: #a855f7; background: rgba(168, 85, 247, 0.1); }
.alert-warning { border-left-color: var(--warning); background: var(--warning-bg); }
.alert-caution { border-left-color: var(--danger); background: var(--danger-bg); }

blockquote {
  margin: 1.5rem 0;
  padding: 0.75rem 1.25rem;
  border-left: 4px solid var(--accent);
  background: var(--bg-surface);
  border-radius: 0 8px 8px 0;
  color: var(--text-secondary);
}
blockquote p:last-child { margin-bottom: 0; }

/* ---------------- MATH EXPRESSIONS ---------------- */
.math-block {
  margin: 1.5rem 0;
  padding: 1rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  text-align: center;
  overflow-x: auto;
}
.math-expr, .math-inline {
  font-family: 'Cambria Math', 'STIX Two Math', 'Times New Roman', serif;
  font-style: italic;
  letter-spacing: 0.03em;
}
.math-block .math-expr {
  font-size: 1.15em;
  color: var(--accent);
}
.math-inline {
  color: var(--accent);
  padding: 0 0.15rem;
}

/* ---------------- DIAGRAMS & FIGURES ---------------- */
.diagram-figure {
  margin: 2rem 0;
  text-align: center;
}
.diagram-figure img {
  max-width: 100%;
  height: auto;
  border-radius: 8px;
  background: #0f172a;
  border: 1px solid var(--border-color);
  padding: 0.5rem;
  cursor: zoom-in;
  transition: transform 0.2s, box-shadow 0.2s;
}
.diagram-figure img:hover {
  transform: scale(1.01);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
}
.diagram-caption {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 0.5rem;
  font-style: italic;
}

/* ---------------- PREV / NEXT NAV ---------------- */
.prev-next-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  margin: 3rem 0;
  padding-top: 2rem;
  border-top: 1px solid var(--border-color);
}
.prev-card, .next-card {
  display: flex;
  flex-direction: column;
  padding: 1rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  transition: all 0.2s;
}
.prev-card:hover, .next-card:hover {
  border-color: var(--accent);
  text-decoration: none;
  transform: translateY(-2px);
}
.next-card { text-align: right; }
.nav-direction {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--accent);
  text-transform: uppercase;
}
.nav-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-top: 0.25rem;
}

/* ---------------- FOOTER ---------------- */
.site-footer {
  margin-top: 3rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border-color);
  font-size: 0.85rem;
  color: var(--text-muted);
}
.footer-legal-notice {
  display: flex;
  gap: 1rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 1rem 1.25rem;
  margin-bottom: 1.5rem;
}
.footer-legal-icon { font-size: 1.5rem; }
.footer-legal-text p { margin-bottom: 0.5rem; }
.footer-legal-text p:last-child { margin-bottom: 0; }
.footer-meta {
  text-align: center;
  padding-bottom: 2rem;
}

/* ---------------- RIGHT TOC ---------------- */
.toc-sidebar {
  width: var(--toc-width);
  height: calc(100vh - var(--header-height));
  position: sticky;
  top: var(--header-height);
  padding: 2rem 1.25rem;
  overflow-y: auto;
  flex-shrink: 0;
}
.toc-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-secondary);
  letter-spacing: 0.05em;
  margin-bottom: 1rem;
}
.toc-list {
  list-style: none;
  font-size: 0.82rem;
}
.toc-item {
  margin-bottom: 0.45rem;
}
.toc-level-3 {
  padding-left: 0.85rem;
}
.toc-link {
  color: var(--text-secondary);
  display: block;
  line-height: 1.4;
  transition: color 0.15s;
}
.toc-link:hover, .toc-link.active {
  color: var(--accent);
  text-decoration: none;
}
.toc-footer {
  margin-top: 1.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border-subtle);
}
.back-to-top {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ---------------- SEARCH MODAL ---------------- */
.search-modal-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(4px);
  z-index: 200;
  align-items: flex-start;
  justify-content: center;
  padding-top: 12vh;
}
.search-modal-backdrop.open { display: flex; }
.search-modal-card {
  width: 90%;
  max-width: 640px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  box-shadow: 0 16px 40px rgba(0, 0, 0, 0.5);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  max-height: 70vh;
}
.search-modal-header {
  display: flex;
  align-items: center;
  padding: 0.85rem 1.25rem;
  border-bottom: 1px solid var(--border-color);
  gap: 0.75rem;
}
.search-modal-input {
  flex: 1;
  background: none;
  border: none;
  outline: none;
  font-size: 1.05rem;
  color: var(--text-primary);
  font-family: inherit;
}
.btn-search-close {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1.1rem;
}
.search-results-container {
  overflow-y: auto;
  padding: 0.75rem;
  flex: 1;
}
.search-result-item {
  display: block;
  padding: 0.75rem;
  border-radius: 8px;
  color: var(--text-primary);
  text-decoration: none !important;
  transition: background 0.15s;
}
.search-result-item:hover, .search-result-item.selected {
  background: var(--bg-surface-hover);
}
.result-course-tag {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--accent);
}
.result-title {
  font-weight: 600;
  font-size: 0.95rem;
  margin: 0.2rem 0;
}
.result-match-snippet {
  font-size: 0.8rem;
  color: var(--text-muted);
}
.search-empty-hint {
  padding: 2rem;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.9rem;
}
.search-modal-footer {
  padding: 0.65rem 1.25rem;
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  display: flex;
  gap: 1rem;
  font-size: 0.75rem;
  color: var(--text-muted);
}
.search-shortcut-hint kbd {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 3px;
  padding: 0.1rem 0.35rem;
}

/* ---------------- CRYPTOGRAPHIC PROGRESS SYNC MODAL ---------------- */
.sync-modal-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.75);
  backdrop-filter: blur(4px);
  z-index: 250;
  align-items: flex-start;
  justify-content: center;
  padding-top: 8vh;
  padding-bottom: 4vh;
  overflow-y: auto;
}
.sync-modal-backdrop.open { display: flex; }
.sync-modal-card {
  width: 92%;
  max-width: 680px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 14px;
  box-shadow: 0 20px 50px rgba(0, 0, 0, 0.6);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  max-height: 84vh;
}
.sync-modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1.4rem;
  border-bottom: 1px solid var(--border-color);
  background: var(--bg-secondary);
}
.sync-modal-title {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}
.sync-modal-title h3 {
  margin: 0;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
}
.sync-header-icon {
  font-size: 1.25rem;
}
.btn-sync-close {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1.25rem;
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
  transition: all 0.15s;
}
.btn-sync-close:hover {
  color: var(--text-primary);
  background: var(--bg-surface-hover);
}
.sync-modal-body {
  padding: 1.4rem;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 1.4rem;
}

/* Incoming Link Banner */
.sync-incoming-box {
  background: var(--accent-glow);
  border: 1px solid var(--accent);
  border-radius: 10px;
  padding: 1.1rem 1.2rem;
  display: flex;
  flex-direction: column;
  gap: 0.9rem;
}
.sync-incoming-header {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}
.sync-incoming-badge {
  align-self: flex-start;
  background: var(--accent);
  color: #fff;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 0.2rem 0.55rem;
  border-radius: 4px;
  letter-spacing: 0.05em;
}
.sync-incoming-status {
  font-size: 0.9rem;
  color: var(--text-primary);
  line-height: 1.45;
}
.sync-unlock-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.sync-incoming-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}
.sync-feedback-msg {
  padding: 0.6rem 0.85rem;
  border-radius: 6px;
  font-size: 0.85rem;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
}
.sync-success-alert {
  color: var(--success);
  font-weight: 600;
}

/* Export & Share section */
.sync-section {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.sync-section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.sync-section-title {
  margin: 0;
  font-size: 1rem;
  font-weight: 700;
  color: var(--text-primary);
}
.sync-summary-badge {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--accent);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 0.25rem 0.65rem;
  border-radius: 12px;
}
.sync-description {
  margin: 0;
  font-size: 0.86rem;
  color: var(--text-secondary);
  line-height: 1.5;
}
.sync-field-group {
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}
.sync-field-label {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-primary);
}
.sync-text-input {
  width: 100%;
  padding: 0.55rem 0.8rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 7px;
  color: var(--text-primary);
  font-size: 0.88rem;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s;
}
.sync-text-input:focus {
  border-color: var(--accent);
}
.sync-field-hint {
  font-size: 0.76rem;
  color: var(--text-muted);
  line-height: 1.4;
}
.sync-field-hint code {
  background: var(--bg-secondary);
  padding: 0.1rem 0.3rem;
  border-radius: 3px;
  color: var(--accent);
}

.sync-url-row {
  display: flex;
  gap: 0.5rem;
  align-items: center;
  flex-wrap: wrap;
}
.sync-url-input {
  flex: 1;
  min-width: 220px;
  padding: 0.55rem 0.8rem;
  background: var(--code-bg);
  border: 1px solid var(--border-color);
  border-radius: 7px;
  color: var(--accent);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  outline: none;
}
.sync-copy-feedback {
  font-size: 0.8rem;
  color: var(--success);
  font-weight: 600;
}

.btn-sync-action {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 7px;
  padding: 0.55rem 0.95rem;
  color: var(--text-primary);
  font-size: 0.83rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.18s ease;
  white-space: nowrap;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}
.btn-sync-action:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--bg-surface-hover);
}
.btn-sync-merge {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
.btn-sync-merge:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: #fff;
}
.btn-sync-overwrite {
  background: var(--bg-surface);
  border-color: var(--warning);
  color: var(--warning);
}
.btn-sync-overwrite:hover {
  background: var(--warning);
  color: #fff;
}
.btn-sync-highlight {
  background: var(--success-bg);
  border-color: var(--success);
  color: var(--success);
}
.btn-sync-highlight:hover {
  background: var(--success);
  color: #fff;
}
.btn-sync-unlock {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
.btn-sync-unlock:hover {
  background: var(--accent-hover);
  color: #fff;
}

.sync-input-row {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.sync-manual-wrapper {
  margin-top: 0.5rem;
  border-top: 1px dashed var(--border-color);
  padding-top: 0.8rem;
}
.sync-manual-details {
  border-radius: 6px;
}
.sync-manual-summary {
  cursor: pointer;
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--text-secondary);
  user-select: none;
}
.sync-manual-summary:hover {
  color: var(--accent);
}
.sync-manual-body {
  padding-top: 0.75rem;
}

.sync-modal-footer {
  padding: 0.75rem 1.4rem;
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.sync-security-note {
  font-size: 0.74rem;
  color: var(--text-muted);
}
.btn-sync-footer-close {
  background: none;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  color: var(--text-secondary);
  padding: 0.35rem 0.8rem;
  font-size: 0.8rem;
  cursor: pointer;
  transition: all 0.15s;
}
.btn-sync-footer-close:hover {
  background: var(--bg-surface-hover);
  color: var(--text-primary);
}

/* ---------------- LIGHTBOX MODAL ---------------- */
.lightbox-modal {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.9);
  z-index: 300;
  flex-direction: column;
}
.lightbox-modal.open { display: flex; }
.lightbox-toolbar {
  height: 50px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  background: rgba(15, 23, 42, 0.8);
  border-bottom: 1px solid #334155;
  color: #f8fafc;
}
.lightbox-actions {
  display: flex;
  gap: 0.5rem;
}
.btn-lightbox-action {
  background: #1e293b;
  border: 1px solid #475569;
  color: #fff;
  border-radius: 4px;
  padding: 0.3rem 0.75rem;
  cursor: pointer;
  font-size: 0.85rem;
}
.lightbox-viewport {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: auto;
  padding: 1rem;
}
.lightbox-viewport img {
  max-width: 95%;
  max-height: 85vh;
  transition: transform 0.15s ease-out;
  user-select: none;
}

/* ---------------- RESPONSIVE BREAKPOINTS ---------------- */
@media (max-width: 1200px) {
  .toc-sidebar { display: none; }
  .main-content { padding: 2rem 1.5rem; }
}

@media (max-width: 1024px) {
  .top-quick-links { display: none; }
  .btn-hamburger { display: flex; }
  .site-sidebar {
    position: fixed;
    top: var(--header-height);
    left: calc(-1 * var(--sidebar-width));
    height: calc(100vh - var(--header-height));
    z-index: 150;
    transition: left 0.25s ease;
  }
  .site-sidebar.open {
    left: 0;
    box-shadow: 8px 0 24px rgba(0, 0, 0, 0.5);
  }
  .sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.6);
    z-index: 140;
  }
  .sidebar-backdrop.open { display: block; }
  .main-content { padding: 1.5rem 1rem; }
  .prev-next-nav { grid-template-columns: 1fr; }
}

@media (max-width: 640px) {
  .btn-author { display: none; }
  .font-size-controls { display: none; }
  .kbd-shortcut { display: none; }
  .article-body h1 { font-size: 1.65rem; }
  .article-body h2 { font-size: 1.35rem; }
  .lesson-completion-banner { flex-direction: column; align-items: flex-start; }
  .sync-modal-backdrop {
    padding-top: 3vh;
    padding-bottom: 2vh;
  }
  .sync-modal-card {
    width: 96%;
    max-height: 90vh;
  }
  .sync-modal-header {
    padding: 0.8rem 1rem;
  }
  .sync-modal-title h3 {
    font-size: 0.95rem;
  }
  .sync-modal-body {
    padding: 1rem;
    gap: 1rem;
  }
  .sync-incoming-actions {
    flex-direction: column;
  }
  .sync-incoming-actions .btn-sync-action {
    width: 100%;
    justify-content: center;
  }
  .sync-url-row {
    flex-direction: column;
    align-items: stretch;
  }
  .sync-url-row .btn-sync-action {
    width: 100%;
    justify-content: center;
  }
  .sync-input-row {
    flex-direction: column;
    align-items: stretch;
  }
  .sync-modal-footer {
    flex-direction: column;
    align-items: stretch;
    text-align: center;
  }
  .btn-sync-footer-close {
    width: 100%;
  }
}