/* =====================================================================
   BỘ GIẢI LAB JAVA - STYLESHEET TỐI ƯU (style.css)
   Chuẩn UI/UX: Dark Mode, Typography cân đối, Concentric Radius,
   Sticky Navigation, Card Elevation, Code Highlighter cao cấp.
   ===================================================================== */

:root {
  /* --- Light Mode (Default) --- */
  --bottomnav-h: 52px;
  --bg-page: #f8fafc;
  --bg-surface: #ffffff;
  --bg-muted: #f1f5f9;
  --bg-code: #f8fafc;
  --border-color: #e2e8f0;
  --border-hover: #cbd5e1;
  --text-primary: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  --accent: #0284c7;
  --accent-hover: #0369a1;
  --accent-subtle: #f0f9ff;
  --accent-border: #bae6fd;
  --success: #16a34a;
  --success-subtle: #f0fdf4;
  --success-border: #bbf7d0;
  --warning: #d97706;
  --danger: #dc2626;
  --topbar-bg: rgba(15, 23, 42, 0.94);
  --topbar-text: #ffffff;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.07), 0 2px 4px -2px rgb(0 0 0 / 0.06);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.08), 0 4px 6px -4px rgb(0 0 0 / 0.04);
}

[data-theme="dark"] {
  /* --- Dark Mode --- */
  --bg-page: #0b1120;
  --bg-surface: #1e293b;
  --bg-muted: #0f172a;
  --bg-code: #141e33;
  --border-color: #334155;
  --border-hover: #475569;
  --text-primary: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --accent: #38bdf8;
  --accent-hover: #7dd3fc;
  --accent-subtle: rgba(56, 189, 248, 0.12);
  --accent-border: rgba(56, 189, 248, 0.28);
  --success: #4ade80;
  --success-subtle: rgba(74, 222, 128, 0.1);
  --success-border: rgba(74, 222, 128, 0.25);
  --warning: #fbbf24;
  --danger: #f87171;
  --topbar-bg: rgba(15, 23, 42, 0.95);
  --topbar-text: #ffffff;
  --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
  --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.3);
  --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.3);
}

/* Base reset & Typography */
* { box-sizing: border-box; }

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  font-size: 16px;
  line-height: 1.68;
  color: var(--text-primary);
  background-color: var(--bg-page);
  transition: background-color 0.25s ease, color 0.25s ease;
  padding-bottom: calc(var(--bottomnav-h) + 84px);
}

/* Ẩn tiêu đề lặp do Pandoc tự động sinh */
#title-block-header {
  display: none !important;
}

/* Thanh tiến độ đọc bài */
#reading-progress {
  position: fixed;
  top: auto;
  bottom: var(--bottomnav-h);
  left: 0;
  height: 3px;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), #38bdf8);
  z-index: 100;
  transition: width 0.1s ease-out;
}

/* Bottombar điều hướng (cố định đáy trang) */
.topbar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--bottomnav-h);
  padding: 0 24px;
  background: var(--topbar-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  box-shadow: 0 -4px 16px rgba(0, 0, 0, 0.2);
  color: var(--topbar-text);
  font-size: 14.5px;
}

.topbar-left {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.topbar a.topbar-back {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: #93c5fd;
  text-decoration: none;
  font-weight: 500;
  padding: 4px 8px;
  border-radius: 6px;
  transition: background 0.15s ease, color 0.15s ease;
}

.topbar a.topbar-back:hover {
  color: #ffffff;
  background: rgba(255, 255, 255, 0.1);
}

.topbar .sep {
  opacity: 0.3;
}

.topbar .title {
  font-weight: 600;
  color: #ffffff;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

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

/* Nút chuyển Dark/Light Mode */
.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  padding: 0;
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.08);
  color: #ffffff;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, transform 0.1s ease;
}

.icon-btn:hover {
  background: rgba(255, 255, 255, 0.18);
  border-color: rgba(255, 255, 255, 0.35);
}

.icon-btn:active {
  transform: scale(0.94);
}

/* Layout container chính - Đã sửa lỗi mất max-width */
main, .content-wrapper {
  max-width: 920px;
  margin: 0 auto;
  padding: 32px 24px 90px;
}

/* Headings */
h1 {
  font-size: 28px;
  line-height: 1.3;
  margin: 16px 0 20px;
  color: var(--text-primary);
  font-weight: 700;
  letter-spacing: -0.02em;
  text-wrap: balance;
  border-bottom: 2px solid var(--border-color);
  padding-bottom: 12px;
}

h2 {
  font-size: 21px;
  line-height: 1.35;
  margin: 40px 0 16px;
  color: var(--text-primary);
  font-weight: 650;
  letter-spacing: -0.015em;
  text-wrap: balance;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 8px;
}

h3 {
  font-size: 17.5px;
  margin: 28px 0 12px;
  color: var(--text-primary);
  font-weight: 600;
  text-wrap: balance;
}

h4 {
  font-size: 15.5px;
  margin: 22px 0 10px;
  color: var(--text-secondary);
  font-weight: 600;
}

h1, h2, h3, h4 {
  scroll-margin-top: 72px;
}

p, li {
  color: var(--text-secondary);
  text-wrap: pretty;
}

a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.15s ease;
}

a:hover {
  color: var(--accent-hover);
  text-decoration: underline;
}

/* Inline code & code blocks */
code {
  font-family: 'JetBrains Mono', 'Cascadia Code', Consolas, Monaco, monospace;
  font-size: 13.5px;
  background: var(--bg-muted);
  color: var(--accent);
  padding: 2px 6px;
  border-radius: 5px;
  border: 1px solid var(--border-color);
}

/* Khối mã nguồn nâng cao */
.code-block-wrapper {
  margin: 20px 0;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  overflow: hidden;
  background: var(--bg-code);
  box-shadow: var(--shadow-sm);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.code-block-wrapper:hover {
  border-color: var(--border-hover);
}

.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 7px 14px;
  background: var(--bg-muted);
  border-bottom: 1px solid var(--border-color);
  font-size: 13px;
  color: var(--text-muted);
  user-select: none;
}

.code-header-title {
  display: flex;
  align-items: center;
  gap: 7px;
  font-family: 'JetBrains Mono', Consolas, monospace;
  font-weight: 600;
  color: var(--text-secondary);
}

.code-file-icon {
  font-size: 14px;
}

.code-lang-badge {
  display: inline-block;
  padding: 1px 7px;
  border-radius: 4px;
  background: var(--accent-subtle);
  color: var(--accent);
  font-size: 11.5px;
  font-weight: 600;
  text-transform: uppercase;
}

.code-copy-btn {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 4px 10px;
  border-radius: 5px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-secondary);
  font-size: 12px;
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease, transform 0.1s ease;
}

.code-copy-btn:hover {
  background: var(--accent-subtle);
  color: var(--accent);
  border-color: var(--accent-border);
}

.code-copy-btn:active {
  transform: scale(0.96);
}

.code-copy-btn.copied {
  background: var(--success-subtle);
  color: var(--success);
  border-color: var(--success-border);
  font-weight: 600;
}

pre {
  margin: 0;
  padding: 14px 16px;
  overflow-x: auto;
  line-height: 1.5;
  background: transparent;
}

pre code {
  background: transparent;
  padding: 0;
  border: none;
  font-size: 13.5px;
  color: inherit;
}

/* Syntax Highlighting Dark Mode overrides */
[data-theme="dark"] div.sourceCode { background-color: var(--bg-code) !important; }
[data-theme="dark"] code span.kw { color: #93c5fd !important; font-weight: 600; }
[data-theme="dark"] code span.dt { color: #67e8f9 !important; }
[data-theme="dark"] code span.dv,
[data-theme="dark"] code span.bn,
[data-theme="dark"] code span.fl { color: #fca5a5 !important; }
[data-theme="dark"] code span.ch,
[data-theme="dark"] code span.st { color: #86efac !important; }
[data-theme="dark"] code span.co { color: #94a3b8 !important; font-style: italic; }
[data-theme="dark"] code span.fu { color: #fde047 !important; }
[data-theme="dark"] code span.bu { color: #c084fc !important; }
[data-theme="dark"] code span.im { color: #f472b6 !important; }
[data-theme="dark"] code span.op { color: #cbd5e1 !important; }

/* Bảng số liệu - Tabular Numbers */
table {
  border-collapse: separate;
  border-spacing: 0;
  width: 100%;
  margin: 20px 0;
  font-size: 14.5px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  background: var(--bg-surface);
}

th, td {
  padding: 9px 13px;
  text-align: left;
  vertical-align: top;
  border-bottom: 1px solid var(--border-color);
  border-right: 1px solid var(--border-color);
}

th:last-child, td:last-child {
  border-right: none;
}

tr:last-child td {
  border-bottom: none;
}

th {
  background: var(--bg-muted);
  font-weight: 650;
  color: var(--text-primary);
  font-size: 13.5px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

td {
  font-variant-numeric: tabular-nums;
  color: var(--text-secondary);
}

tr:hover td {
  background-color: var(--accent-subtle);
}

/* Blockquotes / Callout notes */
blockquote {
  margin: 20px 0;
  padding: 12px 18px;
  border-left: 4px solid var(--accent);
  border-radius: 0 8px 8px 0;
  background: var(--accent-subtle);
  color: var(--text-secondary);
  font-size: 15px;
}

blockquote p {
  margin: 4px 0;
}

/* Mục lục TOC */
#TOC {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 16px 20px;
  margin: 22px 0 32px;
  box-shadow: var(--shadow-sm);
}

.toc-header-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
  font-size: 14.5px;
}

.toc-toggle-btn {
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: 5px;
  padding: 2px 8px;
  font-size: 12px;
  color: var(--text-muted);
  cursor: pointer;
}

.toc-toggle-btn:hover {
  background: var(--bg-muted);
  color: var(--text-primary);
}

#TOC ul {
  margin: 4px 0;
  padding-left: 22px;
  transition: opacity 0.2s ease, max-height 0.2s ease;
}

#TOC ul.is-collapsed {
  display: none;
}

#TOC li {
  margin: 6px 0;
}

#TOC a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 14.5px;
  transition: color 0.15s ease;
}

#TOC a:hover, #TOC a.toc-active {
  color: var(--accent);
  font-weight: 600;
  text-decoration: underline;
}

/* --- AI VOICEOVER AUDIO PLAYER (ZEROTTS) --- */
.audio-player-card {
  margin: 22px 0 28px;
  padding: 16px 20px;
  background: var(--bg-surface);
  border: 1px solid var(--accent-border);
  border-radius: 10px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.2s ease, border-color 0.2s ease;
}

.audio-player-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--accent);
}

.audio-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 12px;
}

.audio-card-title {
  display: flex;
  align-items: center;
  gap: 10px;
}

.audio-icon-badge {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 8px;
  background: var(--accent-subtle);
  color: var(--accent);
  font-size: 18px;
}

.audio-card-title strong {
  display: block;
  font-size: 15px;
  color: var(--text-primary);
}

.audio-meta {
  font-size: 12.5px;
  color: var(--text-muted);
}

.audio-meta span {
  color: var(--accent);
  font-weight: 500;
}

.audio-voice-badge {
  font-size: 11.5px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 2px 8px;
  border-radius: 20px;
  background: var(--accent-subtle);
  color: var(--accent);
  border: 1px solid var(--accent-border);
}

.audio-controls {
  display: flex;
  align-items: center;
  gap: 14px;
}

.audio-play-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 50%;
  border: none;
  background: var(--accent);
  color: #ffffff;
  cursor: pointer;
  box-shadow: 0 2px 4px rgba(2, 132, 199, 0.25);
  transition: transform 0.12s ease, background-color 0.15s ease, box-shadow 0.15s ease;
  flex-shrink: 0;
}

.audio-play-btn:hover {
  background: var(--accent-hover);
  transform: scale(1.05);
}

.audio-play-btn:active {
  transform: scale(0.94);
}

.audio-time-track {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-grow: 1;
}

.audio-time-current,
.audio-time-total {
  font-size: 12.5px;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
  min-width: 38px;
}

.audio-progress-bar {
  position: relative;
  flex-grow: 1;
  height: 6px;
  background: var(--bg-muted);
  border-radius: 3px;
  cursor: pointer;
  overflow: hidden;
}

.audio-progress-fill {
  height: 100%;
  width: 0%;
  background: var(--accent);
  border-radius: 3px;
  transition: width 0.1s linear;
}

.audio-speed-btn {
  padding: 3px 8px;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background: var(--bg-muted);
  color: var(--text-secondary);
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  font-variant-numeric: tabular-nums;
  transition: all 0.15s ease;
  flex-shrink: 0;
}

.audio-speed-btn:hover {
  background: var(--accent-subtle);
  color: var(--accent);
  border-color: var(--accent-border);
}

/* Nút tua 5 giây & Nút bật lời đọc */
.audio-skip-btn,
.audio-transcript-toggle-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 8px;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background: var(--bg-muted);
  color: var(--text-secondary);
  font-size: 12px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s ease;
  flex-shrink: 0;
}

.audio-skip-btn:hover,
.audio-transcript-toggle-btn:hover {
  background: var(--accent-subtle);
  color: var(--accent);
  border-color: var(--accent-border);
}

.audio-skip-btn:active,
.audio-transcript-toggle-btn:active {
  transform: scale(0.95);
}

.audio-transcript-toggle-btn.active {
  background: var(--accent);
  color: #ffffff;
  border-color: var(--accent);
}

/* Dropdown chọn giọng đọc (Voice Picker) */
.voice-picker-wrapper {
  position: relative;
  display: inline-block;
}

.voice-select {
  appearance: none;
  -webkit-appearance: none;
  padding: 4px 24px 4px 10px;
  border-radius: 6px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2364748b' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E") no-repeat right 7px center;
  color: var(--text-secondary);
  font-size: 12.5px;
  font-weight: 500;
  cursor: pointer;
  outline: none;
  transition: all 0.15s ease;
}

.voice-select:hover {
  border-color: var(--accent-border);
  color: var(--accent);
}

.voice-select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px var(--accent-subtle);
}

/* Khung lời đọc & Tô sáng câu đang đọc (Transcript Karaoke) */
.audio-transcript-container {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px dashed var(--border-color);
  transition: all 0.25s ease;
}

.audio-transcript-container.is-collapsed {
  display: none;
}

.audio-transcript-header {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.audio-sentences-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
  max-height: 220px;
  overflow-y: auto;
  padding-right: 6px;
}

.transcript-sentence {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 6px 10px;
  border-radius: 6px;
  border-left: 3px solid transparent;
  color: var(--text-secondary);
  font-size: 14px;
  line-height: 1.5;
  cursor: pointer;
  transition: all 0.2s ease;
}

.transcript-sentence:hover {
  background: var(--bg-muted);
  color: var(--text-primary);
  border-left-color: var(--border-hover);
}

.sentence-time {
  font-size: 11.5px;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
  flex-shrink: 0;
  user-select: none;
}

.sentence-text {
  flex-grow: 1;
}

/* TRẠNG THÁI TÔ SÁNG CÂU ĐANG ĐỌC (ACTIVE SENTENCE HIGHLIGHT) */
.transcript-sentence.is-speaking {
  background: var(--accent-subtle) !important;
  color: var(--accent) !important;
  border-left-color: var(--accent) !important;
  font-weight: 600;
  box-shadow: 0 1px 3px rgba(2, 132, 199, 0.1);
}

.transcript-sentence.is-speaking .sentence-time {
  color: var(--accent);
  font-weight: 700;
}

/* --- STICKY BOTTOM AUDIO PLAYER PANEL --- */
.sticky-audio-bar {
  position: fixed;
  bottom: var(--bottomnav-h);
  left: 0;
  right: 0;
  z-index: 85;
  background: var(--topbar-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid rgba(255, 255, 255, 0.12);
  color: #ffffff;
  padding: 8px 20px;
  box-shadow: 0 -4px 16px rgba(0, 0, 0, 0.25);
  transition: transform 0.25s ease, opacity 0.25s ease;
}

.sticky-audio-bar.is-collapsed-bar {
  transform: translateY(calc(100% - 32px));
}

.sticky-audio-inner {
  max-width: 1140px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

/* Phần trái: Biểu tượng sóng âm & Tiêu đề bài + Câu đang nói */
.sticky-audio-left {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 220px;
  max-width: 320px;
}

.sticky-audio-icon {
  display: flex;
  align-items: flex-end;
  gap: 2.5px;
  height: 20px;
  padding-bottom: 2px;
}

.equalizer-bar {
  width: 3px;
  background: #38bdf8;
  border-radius: 2px;
  height: 6px;
  transition: height 0.15s ease;
}

.sticky-audio-bar.is-playing .equalizer-bar.bar1 {
  animation: soundwave 0.75s ease-in-out infinite alternate;
}
.sticky-audio-bar.is-playing .equalizer-bar.bar2 {
  animation: soundwave 0.65s ease-in-out infinite alternate 0.2s;
}
.sticky-audio-bar.is-playing .equalizer-bar.bar3 {
  animation: soundwave 0.85s ease-in-out infinite alternate 0.4s;
}

@keyframes soundwave {
  0% { height: 4px; }
  100% { height: 18px; }
}

.sticky-track-info {
  overflow: hidden;
}

.sticky-track-title {
  font-size: 13.5px;
  font-weight: 600;
  color: #ffffff;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.sticky-track-subtitle {
  font-size: 12px;
  color: #93c5fd;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* Phần giữa: Cụm nút Play/Skip & Thanh tua tiến độ */
.sticky-audio-center {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  flex-grow: 1;
  max-width: 480px;
}

.sticky-audio-controls {
  display: flex;
  align-items: center;
  gap: 12px;
}

.sticky-play-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: none;
  background: #0284c7;
  color: #ffffff;
  cursor: pointer;
  transition: all 0.15s ease;
}

.sticky-play-btn:hover {
  background: #0369a1;
  transform: scale(1.06);
}

.sticky-skip-btn {
  background: transparent;
  border: none;
  color: #94a3b8;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  padding: 4px 6px;
  border-radius: 4px;
  transition: all 0.15s ease;
}

.sticky-skip-btn:hover {
  color: #ffffff;
  background: rgba(255, 255, 255, 0.1);
}

.sticky-time-track {
  display: flex;
  align-items: center;
  gap: 8px;
  width: 100%;
}

.sticky-time-current,
.sticky-time-total {
  font-size: 11.5px;
  color: #94a3b8;
  font-variant-numeric: tabular-nums;
  min-width: 32px;
}

.sticky-progress-bar {
  position: relative;
  flex-grow: 1;
  height: 5px;
  background: rgba(255, 255, 255, 0.2);
  border-radius: 3px;
  cursor: pointer;
  overflow: hidden;
}

.sticky-progress-fill {
  height: 100%;
  width: 0%;
  background: #38bdf8;
  border-radius: 3px;
  transition: width 0.1s linear;
}

/* Phần phải: Đổi giọng, Tốc độ, Nút mở Lời đọc & Thu gọn */
.sticky-audio-right {
  display: flex;
  align-items: center;
  gap: 8px;
}

.sticky-voice-select {
  appearance: none;
  -webkit-appearance: none;
  padding: 4px 20px 4px 8px;
  border-radius: 6px;
  border: 1px solid rgba(255, 255, 255, 0.2);
  background: rgba(255, 255, 255, 0.08) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='10' viewBox='0 0 24 24' fill='none' stroke='%23ffffff' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E") no-repeat right 6px center;
  color: #ffffff;
  font-size: 12px;
  cursor: pointer;
}

.sticky-voice-select option {
  background: #0f172a;
  color: #ffffff;
}

.sticky-speed-btn,
.sticky-transcript-btn,
.sticky-collapse-btn {
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.18);
  color: #ffffff;
  border-radius: 6px;
  padding: 4px 8px;
  font-size: 12px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.sticky-speed-btn:hover,
.sticky-transcript-btn:hover,
.sticky-collapse-btn:hover {
  background: rgba(255, 255, 255, 0.2);
}

/* Drawer xem lời đọc nổi lên trên Bottom bar */
.sticky-transcript-drawer {
  position: absolute;
  bottom: 100%;
  right: 20px;
  width: 440px;
  max-width: calc(100vw - 40px);
  max-height: 340px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 12px 12px 4px 4px;
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  z-index: 86;
  color: var(--text-primary);
}

.drawer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 14px;
  background: var(--bg-muted);
  border-bottom: 1px solid var(--border-color);
  font-size: 13.5px;
}

.drawer-close-btn {
  background: transparent;
  border: none;
  font-size: 18px;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0 4px;
}

.drawer-sentences {
  padding: 10px 12px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

/* Responsive cho Bottom Bar */
@media (max-width: 768px) {
  .sticky-audio-left { max-width: 140px; min-width: 0; }
  .sticky-track-subtitle { display: none; }
  .sticky-voice-select { display: none; }
  .sticky-transcript-btn { display: none; }
  .sticky-audio-bar { padding: 6px 12px; }
  .sticky-transcript-drawer { right: 10px; width: calc(100vw - 20px); }
}

/* --- TRANG CHỦ (INDEX.HTML) COMPONENTS --- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 12px;
  margin: 24px 0;
}

.stat-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 14px 16px;
  box-shadow: var(--shadow-sm);
}

.stat-card .stat-num {
  font-size: 24px;
  font-weight: 700;
  color: var(--accent);
  font-variant-numeric: tabular-nums;
}

.stat-card .stat-desc {
  font-size: 13px;
  color: var(--text-muted);
  margin-top: 2px;
}

/* Thanh tìm kiếm bài tập */
.search-bar-container {
  margin: 28px 0 16px;
}

.search-input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.search-icon {
  position: absolute;
  left: 14px;
  color: var(--text-muted);
  pointer-events: none;
}

.search-input {
  width: 100%;
  padding: 12px 14px 12px 42px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-primary);
  font-size: 15px;
  outline: none;
  box-shadow: var(--shadow-sm);
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.search-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-subtle);
}

.filter-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 12px;
}

.filter-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.filter-pill {
  padding: 4px 12px;
  border-radius: 20px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-secondary);
  font-size: 13px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.filter-pill:hover {
  border-color: var(--accent-border);
  background: var(--accent-subtle);
  color: var(--accent);
}

.filter-pill.active {
  background: var(--accent);
  color: #ffffff;
  border-color: var(--accent);
  font-weight: 600;
}

#search-result-count {
  font-size: 13px;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}

/* Grid danh sách thẻ Lab */
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
  margin: 20px 0;
}

.card {
  position: relative;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  padding: 16px 18px;
  background: var(--bg-surface);
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: transform 0.18s ease, border-color 0.18s ease, box-shadow 0.18s ease;
}

.card:hover {
  transform: translateY(-2px);
  border-color: var(--accent-border);
  box-shadow: var(--shadow-md);
}

.card.card-completed {
  border-color: var(--success-border);
  background: var(--success-subtle);
}

.card h3 {
  margin: 0 0 8px;
  font-size: 17px;
  line-height: 1.35;
}

.card h3 a {
  color: var(--text-primary);
  text-decoration: none;
}

.card:hover h3 a {
  color: var(--accent);
}

.card p {
  margin: 0 0 14px;
  color: var(--text-muted);
  font-size: 14px;
  line-height: 1.5;
  flex-grow: 1;
}

.card .meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 12.5px;
  color: var(--text-muted);
  padding-top: 10px;
  border-top: 1px solid var(--border-color);
  font-variant-numeric: tabular-nums;
}

.card-done-label {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  cursor: pointer;
  user-select: none;
}

.card-done-label input {
  cursor: pointer;
  accent-color: var(--success);
}

.badge {
  display: inline-block;
  background: var(--accent-subtle);
  color: var(--accent);
  border-radius: 20px;
  padding: 1px 9px;
  font-size: 12px;
  font-weight: 500;
}

/* Nút quay lại đầu trang (nổi trên cả 2 thanh đáy) */
#back-to-top {
  position: fixed;
  bottom: calc(var(--bottomnav-h) + 84px);
  right: 24px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-primary);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  pointer-events: none;
  transform: translateY(10px);
  transition: opacity 0.2s ease, transform 0.2s ease, background 0.15s ease;
  z-index: 40;
}

#back-to-top.visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

#back-to-top:hover {
  background: var(--accent-subtle);
  color: var(--accent);
  border-color: var(--accent-border);
}

/* Điều hướng cuối bài: Bài trước / Bài sau */
.doc-footer-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border-color);
}

.nav-card {
  display: flex;
  flex-direction: column;
  padding: 14px 18px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
  background: var(--bg-surface);
  text-decoration: none !important;
  transition: all 0.15s ease;
}

.nav-card:hover {
  border-color: var(--accent-border);
  background: var(--accent-subtle);
  transform: translateY(-2px);
}

.nav-card.next {
  text-align: right;
  grid-column: 2;
}

.nav-card .nav-sub {
  font-size: 12px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 4px;
}

.nav-card .nav-name {
  font-size: 15px;
  font-weight: 600;
  color: var(--text-primary);
}

.nav-card:hover .nav-name {
  color: var(--accent);
}

/* Responsive Media Queries */
@media (max-width: 768px) {
  main, .content-wrapper {
    padding: 20px 16px 70px;
  }
  h1 { font-size: 24px; }
  h2 { font-size: 19px; }
  .cards { grid-template-columns: 1fr; }
  .doc-footer-nav { grid-template-columns: 1fr; }
  .nav-card.next { text-align: left; grid-column: 1; }
  .topbar { padding: 0 16px; }
}

@media print {
  .topbar, #reading-progress, #back-to-top, .code-copy-btn, .toc-toggle-btn, .doc-footer-nav {
    display: none !important;
  }
  main, .content-wrapper {
    max-width: none;
    padding: 0;
  }
  pre, .code-block-wrapper {
    page-break-inside: avoid;
    border: 1px solid #ccc;
  }
  table {
    page-break-inside: avoid;
  }
}

/* --- 8. PANEL DIEU KHIEN THUYET MINH TOAN TRANG --- */
#narr-fab {
  position: fixed;
  right: 18px;
  bottom: 76px;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  border: 1px solid var(--accent-border);
  background: var(--accent);
  color: #fff;
  font-size: 24px;
  cursor: pointer;
  z-index: 900;
  box-shadow: 0 4px 14px rgba(2, 132, 199, 0.4);
}
#narr-fab:hover { background: var(--accent-hover); }
#narr-panel {
  position: fixed;
  right: 18px;
  bottom: 140px;
  width: 340px;
  max-width: calc(100vw - 36px);
  max-height: min(70vh, 520px);
  display: flex;
  flex-direction: column;
  background: var(--bg-surface);
  color: var(--text-primary);
  border: 1px solid var(--accent-border);
  border-radius: 12px;
  box-shadow: 0 10px 32px rgba(0, 0, 0, 0.25);
  z-index: 901;
  overflow: hidden;
  font-size: 14px;
}
.narr-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 12px;
  background: var(--accent-subtle);
  border-bottom: 1px solid var(--accent-border);
}
.narr-close {
  border: none;
  background: none;
  font-size: 20px;
  cursor: pointer;
  color: var(--text-muted);
}
.narr-row {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px 0;
}
.narr-row span { flex: 0 0 48px; color: var(--text-secondary); }
.narr-row select {
  flex: 1;
  padding: 6px 8px;
  border-radius: 8px;
  border: 1px solid var(--accent-border);
  background: var(--bg-page);
  color: var(--text-primary);
}
.narr-controls {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 12px;
}
.narr-play {
  flex: 0 0 42px;
  height: 42px;
  border-radius: 50%;
  border: none;
  background: var(--accent);
  color: #fff;
  font-size: 18px;
  cursor: pointer;
}
.narr-play:hover { background: var(--accent-hover); }
.narr-track { flex: 1; display: flex; align-items: center; gap: 6px; font-size: 12px; color: var(--text-muted); }
.narr-bar {
  flex: 1;
  height: 6px;
  border-radius: 3px;
  background: var(--bg-muted);
  cursor: pointer;
  overflow: hidden;
}
.narr-fill { height: 100%; width: 0; background: var(--accent); }
.narr-speed {
  border: 1px solid var(--accent-border);
  background: var(--bg-page);
  color: var(--text-primary);
  border-radius: 8px;
  padding: 6px 8px;
  cursor: pointer;
  font-size: 12px;
}
.narr-sentences {
  overflow-y: auto;
  border-top: 1px solid var(--accent-border);
  padding: 8px 12px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.narr-empty { color: var(--text-muted); font-size: 13px; padding: 6px 0; }
.narr-sentence {
  padding: 6px 8px;
  border-radius: 8px;
  cursor: pointer;
  font-size: 13px;
  line-height: 1.5;
  color: var(--text-secondary);
}
.narr-sentence:hover { background: var(--bg-muted); }
.narr-sentence.active { background: var(--accent-subtle); color: var(--text-primary); font-weight: 600; }
@media print {
  #narr-fab, #narr-panel { display: none !important; }
}
.narr-prev, .narr-next {
  flex: 0 0 34px;
  height: 34px;
  border-radius: 8px;
  border: 1px solid var(--accent-border);
  background: var(--bg-page);
  color: var(--text-primary);
  font-size: 15px;
  cursor: pointer;
}
.narr-prev:hover, .narr-next:hover { background: var(--bg-muted); }

/* --- MUC LUC PANEL BEN TRAI (man hinh rong) --- */
@media (min-width: 1280px) {
  #TOC {
    position: fixed;
    left: 0;
    top: 0;
    bottom: var(--bottomnav-h);
    width: 300px;
    margin: 0;
    border-radius: 0;
    border: none;
    border-right: 1px solid var(--border-color);
    box-shadow: none;
    overflow-y: auto;
    padding: 20px 18px 24px;
    z-index: 40;
  }
  main.content-wrapper {
    max-width: 920px;
    margin-left: calc(300px + (100vw - 300px - 920px) / 2);
    margin-right: auto;
  }
  #TOC ul {
    padding-left: 16px;
  }
  #TOC > ul {
    padding-left: 4px;
  }
}
@media print {
  #TOC {
    display: none !important;
  }
}