/* ===================================================================
   CCMUN2026 庆历新政 · 浅色古风主题
   ===================================================================
   基于 MUN Courseware Design System 的组件结构，
   替换颜色变量为暖纸色系，营造淡雅中国风。
   =================================================================== */

/* ========== Design System: 浅色古风 ========== */
:root {
  /* ---- Color Palette ---- */
  --bg-deep: #f5f0e8;            /* main background — 暖纸色 */
  --bg-dark: #ebe5d8;            /* darker surfaces */
  --bg-card: #faf6ee;            /* card backgrounds — 宣纸白 */
  --aged-paper: #5c3d2e;         /* primary text color — 深棕 */
  --muted-gold: #8b6914;         /* accent color — 古铜金 */
  --faded-blue: #2c4a6e;         /* secondary accent — 藏青 */
  --cream: #faf6ee;              /* bright accents */
  --text-primary: #3d3d3d;       /* body text — 深灰 */
  --text-secondary: #6b6b6b;     /* secondary text */
  --text-muted: #9a9080;         /* muted/label text */
  --accent-red: #8b3a3a;         /* warnings, key issues — 朱红 */
  --accent-green: #4a7c59;       /* success — 苍绿 */
  --border-subtle: rgba(92,61,46,0.15);   /* subtle borders */
  --shadow-deep: rgba(0,0,0,0.08);        /* drop shadows — light */
  --overlay-dark: rgba(245,240,232,0.95);  /* overlay backgrounds */
  --player-height: 64px;

  /* ---- Typography ---- */
  --font-heading: 'Noto Serif SC', 'STSong', 'KaiTi', serif;
  --font-body-cn: 'Noto Serif SC', 'STSong', serif;
  --font-body-en: 'Georgia', 'Times New Roman', serif;
  --font-ui: 'Noto Sans SC', 'PingFang SC', sans-serif;
  --font-mono: 'Courier Prime', 'Courier New', monospace;

  /* ---- Spacing Scale (4px base) ---- */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-16: 64px;

  /* ---- Border Radii ---- */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  /* ---- Transitions ---- */
  --transition-fast: 150ms ease;
  --transition-normal: 300ms ease;
  --transition-slow: 500ms ease;
}

/* ========== Reset & Base ========== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-size: 16px;
  overflow: hidden;
}

body {
  font-family: var(--font-body-cn);
  background: var(--bg-deep);
  color: var(--text-primary);
  line-height: 1.8;
  min-height: 100vh;
  overflow: hidden;
}

/* ========== 淡雅纹理背景 ========== */
body::before {
  content: '';
  position: fixed;
  top: 0; left: 0; width: 100%; height: 100%;
  pointer-events: none;
  z-index: 1000;
  opacity: 0.015;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.65' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
}

/* 去掉暗角效果 — 浅色主题不需要 */
body::after {
  content: '';
  position: fixed;
  top: 0; left: 0; width: 100%; height: 100%;
  pointer-events: none;
  z-index: 999;
  background: radial-gradient(ellipse at center, transparent 60%, rgba(92,61,46,0.06) 100%);
}

/* ========== Page Structure ========== */
.page {
  position: fixed;
  top: 0; left: 0; right: 0;
  bottom: var(--player-height);
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
  align-items: center;
  padding: var(--space-8) var(--space-6) var(--space-16);
  overflow-y: auto;
  overflow-x: hidden;
  -webkit-overflow-scrolling: touch;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease, visibility 0.6s ease;
}

.page.active {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateY(0);
  z-index: 1;
}

.page-content { padding-top: var(--space-10); }
.page-title { justify-content: center; padding-top: 0; }

/* Ambient background — 浅色淡雅渐变 */
.page::before {
  content: '';
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background:
    radial-gradient(ellipse at 50% 30%, rgba(139,105,20,0.04) 0%, transparent 50%),
    radial-gradient(ellipse at 75% 75%, rgba(44,74,110,0.05) 0%, transparent 45%),
    radial-gradient(ellipse at 25% 80%, rgba(139,58,58,0.03) 0%, transparent 40%),
    linear-gradient(180deg, #f5f0e8 0%, #ede7da 50%, #f5f0e8 100%);
  z-index: -1;
}

.page-title::before {
  background:
    radial-gradient(ellipse at 50% 25%, rgba(139,105,20,0.08) 0%, transparent 45%),
    radial-gradient(ellipse at 75% 75%, rgba(44,74,110,0.06) 0%, transparent 40%),
    radial-gradient(ellipse at 25% 75%, rgba(139,58,58,0.04) 0%, transparent 40%),
    linear-gradient(180deg, #f5f0e8 0%, #ede7da 50%, #f5f0e8 100%);
}

/* ========== Content Container ========== */
.content-container {
  max-width: 900px;
  width: 100%;
  margin: 0 auto;
  padding: var(--space-6);
  position: relative;
  z-index: 1;
}

/* ========== Typography System ========== */
h1, h2, h3, h4 {
  font-family: var(--font-heading);
  color: var(--aged-paper);
  line-height: 1.4;
  margin-bottom: var(--space-4);
}

h1 {
  font-size: 2.2rem;
  letter-spacing: 2px;
}

h2 {
  font-size: 1.6rem;
  letter-spacing: 1px;
  border-bottom: 2px solid var(--border-subtle);
  padding-bottom: var(--space-3);
  margin-bottom: var(--space-6);
}

h3 {
  font-size: 1.2rem;
  color: var(--accent-red);
  margin-top: var(--space-6);
  margin-bottom: var(--space-3);
}

h4 {
  font-size: 1rem;
  color: var(--faded-blue);
  font-weight: 600;
}

p {
  font-size: 1rem;
  line-height: 1.9;
  color: var(--text-primary);
  margin-bottom: var(--space-4);
  text-align: justify;
}

p:last-child { margin-bottom: 0; }

/* ========== Special Text Elements ========== */
.quote {
  border-left: 4px solid var(--accent-red);
  padding: var(--space-4) var(--space-6);
  margin: var(--space-6) 0;
  background: rgba(139,58,58,0.05);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-style: italic;
  color: var(--text-primary);
  font-size: 1.05rem;
  line-height: 1.8;
}

.quote cite {
  display: block;
  margin-top: var(--space-3);
  font-size: 0.9rem;
  color: var(--accent-red);
  font-style: normal;
}

.highlight {
  color: var(--accent-red);
  font-weight: 600;
}

.key-term {
  display: inline-block;
  background: rgba(139,58,58,0.08);
  color: var(--accent-red);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-sm);
  font-weight: 600;
  border: 1px solid rgba(139,58,58,0.2);
}

.timestamp {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--faded-blue);
  background: rgba(44,74,110,0.08);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  display: inline-block;
  margin-bottom: var(--space-3);
}

/* ========== Cards & Boxes ========== */
.info-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  margin: var(--space-6) 0;
  box-shadow: 0 2px 12px rgba(92,61,46,0.06);
}

.info-card h3 {
  margin-top: 0;
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: var(--space-3);
}

.data-card {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: var(--space-4) var(--space-6);
  margin: var(--space-2);
  min-width: 120px;
  box-shadow: 0 1px 6px rgba(92,61,46,0.06);
}

.data-card .value {
  font-family: var(--font-heading);
  font-size: 1.4rem;
  font-weight: 700;
  color: var(--accent-red);
}

.data-card .label {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: var(--space-1);
  text-align: center;
}

.data-row {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin: var(--space-4) 0;
  justify-content: center;
}

/* ========== Lists ========== */
ul, ol {
  margin: var(--space-4) 0;
  padding-left: var(--space-6);
}

li {
  margin-bottom: var(--space-3);
  color: var(--text-primary);
  line-height: 1.7;
}

li strong { color: var(--aged-paper); }

/* ========== Tables ========== */
table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-6) 0;
  font-size: 0.95rem;
}

th, td {
  padding: var(--space-3) var(--space-4);
  text-align: left;
  border-bottom: 1px solid var(--border-subtle);
}

th {
  background: rgba(139,105,20,0.08);
  color: var(--aged-paper);
  font-weight: 600;
  font-family: var(--font-ui);
  font-size: 0.9rem;
}

tr:hover { background: rgba(139,105,20,0.03); }

/* ========== Table Responsive Wrapper ========== */
.table-wrapper {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: var(--space-6) 0;
  scrollbar-width: thin;
  scrollbar-color: rgba(92,61,46,0.2) transparent;
}
.table-wrapper table { margin: 0; min-width: 600px; }

/* ========== Image Containers ========== */
.image-container {
  margin: var(--space-6) 0;
  text-align: center;
}

.lecture-image {
  max-width: 100%;
  width: auto;
  height: auto;
  max-height: 60vh;
  border-radius: var(--radius-lg);
  border: 2px solid var(--border-subtle);
  box-shadow: 0 4px 16px rgba(92,61,46,0.1);
  object-fit: contain;
}

.image-caption {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: var(--space-3);
  font-style: italic;
  line-height: 1.5;
}

/* ========== Image Layout Variants ========== */
.split-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-8);
  margin: var(--space-6) 0;
  align-items: center;
}
.split-layout .image-container { margin: 0; }
.split-layout .image-container .lecture-image {
  width: 100%;
  object-fit: cover;
  max-height: 45vh;
}

.split-layout.split-reverse { direction: rtl; }
.split-layout.split-reverse > * { direction: ltr; }

.image-grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
  margin: var(--space-6) 0;
}
.image-grid-2 .image-container { margin: 0; }

.image-banner {
  margin: var(--space-6) 0;
  text-align: center;
  width: 100%;
}
.image-banner .lecture-image {
  max-width: 100%;
  width: auto;
  max-height: 55vh;
  object-fit: contain;
  border-radius: var(--radius-lg);
  border: 2px solid var(--border-subtle);
  box-shadow: 0 4px 16px rgba(92,61,46,0.1);
}

.image-inset {
  max-width: 70%;
  margin: var(--space-6) auto;
}
.image-inset .lecture-image { max-height: 35vh; }

/* ========== Page Overflow Indicator ========== */
.page-overflow-indicator {
  position: sticky;
  bottom: 0;
  height: 40px;
  margin-top: -40px;
  background: transparent;
  pointer-events: none;
  z-index: 2;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  transition: opacity 0.5s ease;
}

.page-overflow-indicator::before,
.page-overflow-indicator::after {
  content: '';
  width: 13px;
  height: 13px;
  border-right: 2px solid var(--muted-gold);
  border-bottom: 2px solid var(--muted-gold);
  animation: indicator-drift 2.4s ease-in-out infinite;
}

.page-overflow-indicator::before { opacity: 0.55; }
.page-overflow-indicator::after { opacity: 0.75; }
.page-overflow-indicator.hidden { opacity: 0; }

@keyframes indicator-drift {
  0%, 100% { transform: rotate(45deg) translateY(0); }
  50% { transform: rotate(45deg) translateY(4px); }
}

/* ========== Navigation Arrows ========== */
.nav-arrow {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  width: 48px;
  height: 48px;
  background: rgba(250,246,238,0.9);
  border: 1px solid var(--border-subtle);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  z-index: 100;
  transition: all var(--transition-normal);
  backdrop-filter: blur(8px);
  box-shadow: 0 2px 8px rgba(92,61,46,0.08);
}

.nav-arrow:hover {
  background: rgba(139,105,20,0.1);
  border-color: var(--muted-gold);
  transform: translateY(-50%) scale(1.1);
}

.nav-arrow svg { width: 24px; height: 24px; fill: var(--aged-paper); }
.nav-arrow.prev { left: var(--space-4); }
.nav-arrow.next { right: var(--space-4); }

/* ========== Page Indicator Dots ========== */
.page-indicator {
  position: fixed;
  right: var(--space-4);
  top: 50%;
  transform: translateY(-50%);
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  z-index: 100;
}

.page-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: rgba(92,61,46,0.15);
  border: 1px solid rgba(92,61,46,0.3);
  cursor: pointer;
  transition: all var(--transition-normal);
}

.page-dot.active {
  background: var(--accent-red);
  transform: scale(1.3);
  box-shadow: 0 0 8px rgba(139,58,58,0.3);
}

.page-dot:hover { background: rgba(139,58,58,0.4); }

/* ========== Audio Player ========== */
.audio-player {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  height: var(--player-height);
  background: rgba(250,246,238,0.97);
  backdrop-filter: blur(12px);
  border-top: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  padding: 0 var(--space-6);
  gap: var(--space-4);
  z-index: 1000;
}

.audio-player .play-btn {
  width: 40px; height: 40px;
  border-radius: 50%;
  border: 2px solid var(--accent-red);
  background: transparent;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
  flex-shrink: 0;
}

.audio-player .play-btn:hover { background: var(--accent-red); }
.audio-player .play-btn svg { width: 18px; height: 18px; fill: var(--accent-red); transition: fill var(--transition-fast); }
.audio-player .play-btn:hover svg { fill: #fff; }

.progress-container { flex: 1; display: flex; flex-direction: column; gap: var(--space-1); }

.progress-bar {
  width: 100%; height: 4px;
  background: rgba(92,61,46,0.12);
  border-radius: 2px;
  cursor: pointer;
  position: relative;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--faded-blue), var(--accent-red));
  border-radius: 2px;
  width: 0%;
  transition: width 0.1s linear;
  position: relative;
}

.progress-fill::after {
  content: '';
  position: absolute;
  right: -6px; top: 50%;
  transform: translateY(-50%);
  width: 12px; height: 12px;
  background: var(--accent-red);
  border-radius: 50%;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.progress-bar:hover .progress-fill::after { opacity: 1; }

.progress-markers {
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 100%;
  pointer-events: none;
}

.progress-marker {
  position: absolute;
  top: -2px;
  width: 2px;
  height: 8px;
  background: rgba(139,58,58,0.3);
  border-radius: 1px;
}

.time-display {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--text-muted);
  display: flex;
  justify-content: space-between;
}

.volume-control {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.volume-slider {
  width: 80px; height: 4px;
  -webkit-appearance: none;
  background: rgba(92,61,46,0.12);
  border-radius: 2px;
  outline: none;
}

.volume-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 12px; height: 12px;
  background: var(--accent-red);
  border-radius: 50%;
  cursor: pointer;
}

/* ========== Subtitle Toggle Button ========== */
.subtitle-toggle {
  background: transparent;
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-sm);
  padding: var(--space-1);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
  flex-shrink: 0;
}

.subtitle-toggle:hover {
  background: rgba(139,58,58,0.08);
  border-color: var(--accent-red);
}

.subtitle-toggle.active svg { fill: var(--accent-red); }

/* ========== Movie-Style Subtitle Container ========== */
.subtitle-container {
  position: fixed;
  bottom: calc(var(--player-height) + 12px);
  left: 50%;
  transform: translateX(-50%);
  width: 90%;
  max-width: 800px;
  text-align: center;
  z-index: 1001;
  pointer-events: none;
  padding: var(--space-3) var(--space-6);
  background: rgba(61, 61, 61, 0.88);
  border-radius: var(--radius-md);
  transition: opacity 0.3s ease;
}

.subtitle-container.hidden { opacity: 0; }

.subtitle-en {
  font-family: 'Georgia', 'Times New Roman', serif;
  font-size: 0.95rem;
  color: #e8dcc8;
  line-height: 1.5;
  margin-bottom: var(--space-1);
}

.subtitle-zh {
  font-family: 'Noto Serif SC', 'STSong', serif;
  font-size: 1.1rem;
  color: #ffffff;
  line-height: 1.5;
}

.subtitle-container.single-lang .subtitle-en { display: none; }
.subtitle-container.single-lang .subtitle-zh { font-size: 1.2rem; }

/* ========== Title Page Specific ========== */
.title-page { text-align: center; }

.title-page h1 {
  font-size: 2.5rem;
  margin-bottom: var(--space-4);
  background: linear-gradient(135deg, var(--accent-red), var(--aged-paper));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  color: transparent;
  background-clip: text;
}

.title-subtitle {
  font-size: 1.2rem;
  color: var(--text-secondary);
  margin-bottom: var(--space-8);
}

.objectives { text-align: left; max-width: 700px; margin: 0 auto; }
.objectives h3 { text-align: center; margin-bottom: var(--space-6); }
.objectives ul { list-style: none; padding: 0; }

.objectives li {
  padding: var(--space-3) var(--space-4);
  border-left: 3px solid var(--faded-blue);
  margin-bottom: var(--space-3);
  background: rgba(44,74,110,0.05);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  transition: all var(--transition-normal);
}

.objectives li:hover {
  background: rgba(44,74,110,0.1);
  border-left-color: var(--accent-red);
}

/* ========== Keyboard Focus ========== */
.nav-arrow:focus, .page-dot:focus, .play-btn:focus, .subtitle-toggle:focus {
  outline: 2px solid var(--accent-red);
  outline-offset: 2px;
}

/* ========== Scrollbar ========== */
::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--bg-deep); }
::-webkit-scrollbar-thumb { background: rgba(92,61,46,0.2); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: rgba(92,61,46,0.35); }

/* ========== Responsive ========== */
@media (min-width: 1200px) {
  .content-container { max-width: 1000px; }
  .lecture-image { max-height: 75vh; }
}

@media (max-width: 1024px) {
  :root { --player-height: 56px; }
  .nav-arrow { width: 40px; height: 40px; }
  .nav-arrow svg { width: 20px; height: 20px; }
  .page-indicator { right: var(--space-3); }
  .page-dot { width: 8px; height: 8px; }
  .lecture-image { max-height: 40vh; }
  .content-container { max-width: 90vw; }
  h1 { font-size: 2rem; }
  h2 { font-size: 1.4rem; }
  .subtitle-en { font-size: 0.85rem; }
  .subtitle-zh { font-size: 1rem; }
}

@media (max-width: 768px) {
  :root { --player-height: 48px; }
  .page { padding: var(--space-6) var(--space-4) var(--space-12); }
  h1 { font-size: 1.6rem; }
  h2 { font-size: 1.2rem; }
  .content-container { max-width: 100%; padding: var(--space-3); }
  .nav-arrow { width: 36px; height: 36px; top: auto; bottom: calc(var(--player-height) + var(--space-4)); transform: none; }
  .nav-arrow.prev { left: var(--space-2); }
  .nav-arrow.next { right: var(--space-2); }
  .page-indicator { top: auto; bottom: calc(var(--player-height) + var(--space-2)); right: 50%; transform: translateX(50%); flex-direction: row; gap: var(--space-2); }
  .audio-player { height: var(--player-height); padding: 0 var(--space-3); }
  .volume-control { display: none; }
  .data-card { min-width: 80px; padding: var(--space-2) var(--space-3); }
  .data-card .value { font-size: 1rem; }
  .data-card .label { font-size: 0.7rem; }
  .split-layout { grid-template-columns: 1fr; gap: var(--space-4); }
  .split-layout.split-reverse { direction: ltr; }
  .image-banner { margin: var(--space-4) calc(-1 * var(--space-3)); }
  .image-inset { max-width: 100%; }
  .subtitle-container { width: 95%; padding: var(--space-2) var(--space-4); }
  .subtitle-en { font-size: 0.8rem; }
  .subtitle-zh { font-size: 0.95rem; }
}

@media (max-width: 375px) {
  h1 { font-size: 1.4rem; }
  .lecture-image { max-height: 25vh; }
}