/* ==========================================================================
   CSS Variables & Themes
   ========================================================================== */
:root {
  --font-serif: "Noto Serif TC", "Songti TC", "PMingLiU", serif;
  --font-sans: "Noto Sans TC", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-brand: "Cinzel", "Noto Serif TC", serif;

  --font-size-base: 19px;
  --line-height-base: 1.85;
  --paragraph-spacing: 1.25em;

  --sidebar-width: 320px;
  --header-height: 56px;
  --toolbar-height: 52px;
  --max-content-width: 820px;
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --transition-speed: 0.25s;
}

/* 1. Theme: Sepia (Default - 復古羊皮紙) */
body.theme-sepia {
  --bg-primary: #fbf7ee;
  --bg-secondary: #f3ecdc;
  --bg-sidebar: #eae2cf;
  --bg-hover: #dfd5be;
  --bg-active: #d5c8ad;
  --text-primary: #322923;
  --text-secondary: #6e6155;
  --text-muted: #998a7c;
  --border-color: #ded4c0;
  --accent-color: #9d3a24;
  --accent-hover: #b8432a;
  --accent-text: #ffffff;
  --card-shadow: 0 4px 18px rgba(78, 59, 45, 0.08);
}

/* 2. Theme: Light (典雅白) */
body.theme-light {
  --bg-primary: #ffffff;
  --bg-secondary: #f8fafc;
  --bg-sidebar: #f1f5f9;
  --bg-hover: #e2e8f0;
  --bg-active: #cbd5e1;
  --text-primary: #1e293b;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --border-color: #e2e8f0;
  --accent-color: #2563eb;
  --accent-hover: #1d4ed8;
  --accent-text: #ffffff;
  --card-shadow: 0 4px 18px rgba(0, 0, 0, 0.05);
}

/* 3. Theme: Warm (護眼米黃) */
body.theme-warm {
  --bg-primary: #faf6ea;
  --bg-secondary: #f1ebd8;
  --bg-sidebar: #e8dfc7;
  --bg-hover: #dbd0b4;
  --bg-active: #cec1a0;
  --text-primary: #2d261e;
  --text-secondary: #5c5040;
  --text-muted: #8c7c66;
  --border-color: #dbcfb3;
  --accent-color: #a45a2a;
  --accent-hover: #bd6931;
  --accent-text: #ffffff;
  --card-shadow: 0 4px 18px rgba(60, 45, 25, 0.07);
}

/* 4. Theme: Night (深邃夜讀) */
body.theme-night {
  --bg-primary: #16181d;
  --bg-secondary: #1f232b;
  --bg-sidebar: #1a1d24;
  --bg-hover: #292e39;
  --bg-active: #343b49;
  --text-primary: #dbe2ef;
  --text-secondary: #9aa5b8;
  --text-muted: #626e82;
  --border-color: #2a303c;
  --accent-color: #e09f58;
  --accent-hover: #f3b068;
  --accent-text: #1a1d24;
  --card-shadow: 0 4px 18px rgba(0, 0, 0, 0.35);
}

/* 5. Theme: Slate (青石冷硯) */
body.theme-slate {
  --bg-primary: #232b32;
  --bg-secondary: #2c363f;
  --bg-sidebar: #28313a;
  --bg-hover: #37434e;
  --bg-active: #43515e;
  --text-primary: #dce5eb;
  --text-secondary: #99aab7;
  --text-muted: #647583;
  --border-color: #384550;
  --accent-color: #4da6a0;
  --accent-hover: #5ec0ba;
  --accent-text: #1b2228;
  --card-shadow: 0 4px 18px rgba(0, 0, 0, 0.3);
}

/* Font styles */
body.font-serif {
  font-family: var(--font-serif);
}
body.font-sans {
  font-family: var(--font-sans);
}

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

html, body {
  height: 100%;
  overflow: hidden;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  transition: background-color var(--transition-speed), color var(--transition-speed);
}

/* ==========================================================================
   Layout Structure
   ========================================================================== */
.app-layout {
  display: flex;
  height: 100vh;
  width: 100vw;
  overflow: hidden;
}

/* Mobile Header (Hidden on Desktop) */
.mobile-header {
  display: none;
  height: var(--header-height);
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  padding: 0 16px;
  align-items: center;
  justify-content: space-between;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
}

.mobile-title {
  font-size: 16px;
  font-weight: 700;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 60%;
  text-align: center;
}

.icon-btn {
  background: none;
  border: none;
  color: var(--text-primary);
  cursor: pointer;
  padding: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
}
.icon-btn:hover {
  background-color: var(--bg-hover);
}

/* Sidebar Navigation */
.sidebar {
  width: var(--sidebar-width);
  height: 100vh;
  background-color: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  transition: transform var(--transition-speed) ease;
  z-index: 90;
}

.sidebar-header {
  padding: 20px 18px 16px;
  display: flex;
  align-items: center;
  gap: 12px;
  border-bottom: 1px solid var(--border-color);
}

.logo-badge {
  font-family: var(--font-brand);
  background: var(--accent-color);
  color: var(--accent-text);
  font-size: 16px;
  font-weight: 800;
  padding: 6px 10px;
  border-radius: var(--radius-md);
  letter-spacing: 1px;
}

.logo-title h1 {
  font-size: 19px;
  font-weight: 900;
  letter-spacing: 1px;
  color: var(--text-primary);
  line-height: 1.2;
}

.logo-title .subtitle {
  font-size: 12px;
  color: var(--text-muted);
  letter-spacing: 0.5px;
}

.search-box {
  position: relative;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-color);
}

.search-box .search-icon {
  position: absolute;
  left: 26px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  pointer-events: none;
}

.search-box input {
  width: 100%;
  padding: 8px 12px 8px 34px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  font-size: 13px;
  color: var(--text-primary);
  outline: none;
  transition: border-color var(--transition-speed);
}

.search-box input:focus {
  border-color: var(--accent-color);
}

.chapter-meta-summary {
  padding: 8px 18px;
  font-size: 12px;
  color: var(--text-secondary);
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
}

.chapter-list {
  flex: 1;
  overflow-y: auto;
  padding: 8px;
}

.chapter-item {
  display: flex;
  flex-direction: column;
  padding: 10px 14px;
  margin-bottom: 4px;
  border-radius: var(--radius-md);
  cursor: pointer;
  text-decoration: none;
  color: var(--text-primary);
  transition: all 0.15s ease;
  border: 1px solid transparent;
}

.chapter-item:hover {
  background-color: var(--bg-hover);
}

.chapter-item.active {
  background-color: var(--bg-active);
  border-color: var(--accent-color);
  border-left: 4px solid var(--accent-color);
  font-weight: 700;
}

.chapter-item-title {
  font-size: 14px;
  line-height: 1.4;
  margin-bottom: 2px;
}

.chapter-item-meta {
  display: flex;
  justify-content: space-between;
  font-size: 11px;
  color: var(--text-muted);
}

/* Main Content Area */
.content-area {
  flex: 1;
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background-color: var(--bg-primary);
}

/* Top Toolbar */
.top-toolbar {
  height: var(--toolbar-height);
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
  flex-shrink: 0;
  font-size: 13px;
}

.reading-progress-info {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--text-secondary);
  font-weight: 500;
}

.ch-char-count {
  font-size: 12px;
  color: var(--text-muted);
  background: var(--bg-primary);
  padding: 2px 8px;
  border-radius: 10px;
  border: 1px solid var(--border-color);
}

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

.tool-group {
  display: flex;
  align-items: center;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 2px;
}

.tool-group button {
  background: none;
  border: none;
  color: var(--text-primary);
  padding: 4px 8px;
  font-size: 12px;
  cursor: pointer;
  border-radius: var(--radius-sm);
  transition: background var(--transition-speed);
}

.tool-group button:hover {
  background: var(--bg-hover);
}

.font-size-group span {
  padding: 0 4px;
  font-size: 12px;
  color: var(--text-muted);
  min-width: 36px;
  text-align: center;
}

.text-toggle-btn {
  font-weight: 600;
  padding: 4px 10px !important;
}

/* Themes circle buttons */
.theme-group {
  gap: 6px;
  padding: 4px 6px;
  background: transparent;
  border: none;
}

.theme-btn {
  width: 22px;
  height: 22px;
  border-radius: 50%;
  border: 2px solid transparent;
  cursor: pointer;
  padding: 0 !important;
  transition: transform 0.15s;
}

.theme-btn:hover {
  transform: scale(1.15);
}

.theme-btn.active {
  border-color: var(--text-primary) !important;
  box-shadow: 0 0 0 1px var(--bg-secondary);
}

.theme-btn-sepia { background: #fbf7ee; border: 1px solid #d5c8ad; }
.theme-btn-light { background: #ffffff; border: 1px solid #cbd5e1; }
.theme-btn-warm  { background: #faf6ea; border: 1px solid #cec1a0; }
.theme-btn-night { background: #16181d; border: 1px solid #343b49; }
.theme-btn-slate { background: #232b32; border: 1px solid #43515e; }

/* Article Reader Container */
.reader-container {
  flex: 1;
  overflow-y: auto;
  padding: 40px 24px 80px;
  scroll-behavior: smooth;
}

.chapter-body {
  max-width: var(--max-content-width);
  margin: 0 auto;
  font-size: var(--font-size-base);
  line-height: var(--line-height-base);
  letter-spacing: 0.02em;
}

/* Markdown typography rendering */
.chapter-body h1 {
  font-size: 1.85em;
  font-weight: 900;
  margin-bottom: 1.2em;
  padding-bottom: 0.4em;
  border-bottom: 2px solid var(--border-color);
  color: var(--text-primary);
  line-height: 1.3;
}

.chapter-body h2 {
  font-size: 1.4em;
  font-weight: 700;
  margin-top: 1.8em;
  margin-bottom: 0.8em;
  color: var(--accent-color);
}

.chapter-body h3 {
  font-size: 1.15em;
  font-weight: 700;
  margin-top: 1.4em;
  margin-bottom: 0.6em;
}

.chapter-body p {
  margin-bottom: var(--paragraph-spacing);
  text-align: justify;
  text-justify: inter-ideograph;
  text-indent: 2em;
}

.chapter-body blockquote {
  margin: 1.5em 0;
  padding: 12px 20px;
  background-color: var(--bg-secondary);
  border-left: 4px solid var(--accent-color);
  color: var(--text-secondary);
  font-size: 0.95em;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.chapter-body blockquote p {
  text-indent: 0;
  margin-bottom: 0.5em;
}
.chapter-body blockquote p:last-child {
  margin-bottom: 0;
}

.chapter-body hr {
  border: none;
  height: 1px;
  background: var(--border-color);
  margin: 2.5em 0;
}

.chapter-body ul, .chapter-body ol {
  margin: 1em 0 1em 2em;
}

.chapter-body li {
  margin-bottom: 0.5em;
}

.chapter-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5em 0;
  font-size: 0.9em;
}

.chapter-body th, .chapter-body td {
  border: 1px solid var(--border-color);
  padding: 8px 12px;
  text-align: left;
}

.chapter-body th {
  background: var(--bg-secondary);
  font-weight: 700;
}

/* Bottom Chapter Navigation */
.bottom-chapter-nav {
  max-width: var(--max-content-width);
  margin: 60px auto 20px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  padding-top: 30px;
  border-top: 1px solid var(--border-color);
}

.nav-ch-btn {
  flex: 1;
  padding: 14px 20px;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  transition: all 0.2s ease;
}

.nav-ch-btn:hover:not(:disabled) {
  background-color: var(--accent-color);
  color: var(--accent-text);
  border-color: var(--accent-color);
  transform: translateY(-2px);
  box-shadow: var(--card-shadow);
}

.nav-ch-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.nav-btn-catalog {
  flex: 0 0 auto;
  min-width: 100px;
}

/* Floating Scroll to Top */
.floating-actions {
  position: fixed;
  right: 28px;
  bottom: 28px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  z-index: 50;
}

.floating-btn {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  box-shadow: var(--card-shadow);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0.85;
  transition: all 0.2s ease;
}

.floating-btn:hover {
  opacity: 1;
  background: var(--accent-color);
  color: var(--accent-text);
  transform: scale(1.08);
}

/* Mobile Settings Modal */
.settings-modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 200;
  align-items: flex-end;
}

.settings-modal.active {
  display: flex;
}

.modal-content {
  background: var(--bg-secondary);
  width: 100%;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
  padding: 20px;
  max-height: 80vh;
  overflow-y: auto;
  box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.2);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 18px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border-color);
}

.modal-body .setting-item {
  margin-bottom: 20px;
}

.modal-body label {
  display: block;
  font-size: 14px;
  font-weight: 700;
  margin-bottom: 10px;
  color: var(--text-secondary);
}

.button-toggle-row {
  display: flex;
  gap: 10px;
}

.font-option-btn {
  flex: 1;
  padding: 10px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  cursor: pointer;
  font-size: 13px;
}

.font-option-btn.active {
  border-color: var(--accent-color);
  background: var(--bg-active);
  font-weight: 700;
}

/* Sidebar overlay for mobile */
.sidebar-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.4);
  z-index: 85;
}

.sidebar-overlay.active {
  display: block;
}

/* ==========================================================================
   Responsive / Mobile Optimization
   ========================================================================== */
@media (max-width: 768px) {
  .mobile-header {
    display: flex;
  }

  .top-toolbar {
    display: none;
  }

  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    transform: translateX(-100%);
    box-shadow: 4px 0 20px rgba(0, 0, 0, 0.2);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .content-area {
    margin-top: var(--header-height);
    height: calc(100vh - var(--header-height));
  }

  .reader-container {
    padding: 20px 16px 60px;
  }

  .chapter-body {
    font-size: 18px;
    line-height: 1.8;
  }

  .chapter-body h1 {
    font-size: 1.5em;
  }

  .bottom-chapter-nav {
    flex-direction: row;
    gap: 8px;
  }

  .nav-ch-btn {
    padding: 12px 10px;
    font-size: 13px;
  }
}