/* ==========================================================================
   PageFlip Modern Flipbook Stylesheet
   ========================================================================== */

:root {
  --font-main: 'Outfit', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Theme: Slate (Default) */
  --bg-app: #0d0f14;
  --bg-surface: #141721;
  --bg-glass: rgba(22, 26, 38, 0.78);
  --bg-glass-hover: rgba(30, 36, 52, 0.9);
  --border-glass: rgba(255, 255, 255, 0.1);
  --border-glass-bright: rgba(255, 255, 255, 0.22);
  --text-main: #f0f2f8;
  --text-muted: #8c96ac;
  --accent-primary: #4f80ff;
  --accent-gradient: linear-gradient(135deg, #4f80ff, #845ef7);
  --accent-glow: rgba(79, 128, 255, 0.35);
  --desk-gradient: radial-gradient(circle at center, #1b2030 0%, #0d0f14 100%);
  --shadow-elevated: 0 12px 36px -8px rgba(0, 0, 0, 0.65), 0 4px 16px rgba(0, 0, 0, 0.4);
}

[data-theme="wood"] {
  --bg-app: #18120c;
  --bg-surface: #241b12;
  --bg-glass: rgba(38, 28, 20, 0.85);
  --bg-glass-hover: rgba(52, 38, 28, 0.95);
  --border-glass: rgba(240, 200, 160, 0.15);
  --border-glass-bright: rgba(240, 200, 160, 0.3);
  --text-main: #fbf5ee;
  --text-muted: #b8a695;
  --accent-primary: #e67e22;
  --accent-gradient: linear-gradient(135deg, #e67e22, #d35400);
  --accent-glow: rgba(230, 126, 34, 0.35);
  --desk-gradient: radial-gradient(circle at center, #352618 0%, #150f0a 100%);
}

[data-theme="obsidian"] {
  --bg-app: #050608;
  --bg-surface: #0b0d13;
  --bg-glass: rgba(12, 15, 22, 0.88);
  --bg-glass-hover: rgba(20, 24, 36, 0.95);
  --border-glass: rgba(0, 242, 254, 0.18);
  --border-glass-bright: rgba(0, 242, 254, 0.4);
  --text-main: #ffffff;
  --text-muted: #79869c;
  --accent-primary: #00f2fe;
  --accent-gradient: linear-gradient(135deg, #00f2fe, #4facfe);
  --accent-glow: rgba(0, 242, 254, 0.4);
  --desk-gradient: radial-gradient(circle at center, #101524 0%, #030406 100%);
}

[data-theme="blueprint"] {
  --bg-app: #08111e;
  --bg-surface: #0e1e34;
  --bg-glass: rgba(14, 30, 52, 0.85);
  --bg-glass-hover: rgba(20, 42, 72, 0.95);
  --border-glass: rgba(100, 180, 255, 0.2);
  --border-glass-bright: rgba(100, 180, 255, 0.4);
  --text-main: #e8f4ff;
  --text-muted: #88a8cc;
  --accent-primary: #38bdf8;
  --accent-gradient: linear-gradient(135deg, #38bdf8, #0284c7);
  --accent-glow: rgba(56, 189, 248, 0.35);
  --desk-gradient: radial-gradient(circle at center, #142a4a 0%, #060d18 100%);
}

/* Reset & Base */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-font-smoothing: antialiased;
}

html, body {
  width: 100%;
  height: 100%;
  overflow: hidden;
  font-family: var(--font-main);
  background: var(--bg-app);
  color: var(--text-main);
  user-select: none;
  touch-action: manipulation;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

/* Main Layout */
.app-root {
  display: flex;
  flex-direction: column;
  width: 100vw;
  height: 100vh;
  background: var(--desk-gradient);
  position: relative;
  overflow: hidden;
}

/* Header */
.app-header {
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-glass);
  z-index: 50;
  gap: 1rem;
}

.header-left, .header-right {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.header-center {
  flex: 1;
  text-align: center;
  overflow: hidden;
  padding: 0 1rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.brand-icon {
  font-size: 1.4rem;
}

.brand-title {
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.02em;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.book-dropdown, .theme-dropdown {
  background: var(--bg-surface);
  color: var(--text-main);
  border: 1px solid var(--border-glass);
  padding: 0.4rem 0.8rem;
  border-radius: 8px;
  font-family: var(--font-main);
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  outline: none;
  transition: all 0.2s ease;
}

.book-dropdown:hover, .theme-dropdown:hover,
.book-dropdown:focus, .theme-dropdown:focus {
  border-color: var(--accent-primary);
  box-shadow: 0 0 10px var(--accent-glow);
}

.engine-picker-wrapper,
.theme-picker-wrapper {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
}

.picker-label {
  font-family: var(--font-main);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-muted);
  user-select: none;
}

.engine-nav {
  display: inline-flex;
  align-items: center;
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  border-radius: 8px;
  padding: 0.2rem;
  gap: 0.2rem;
}

.engine-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.28rem 0.65rem;
  border-radius: 6px;
  font-family: var(--font-main);
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
  text-decoration: none;
  transition: all 0.2s ease;
  min-width: 32px;
}

.engine-link:hover {
  color: var(--text-main);
  background: rgba(255, 255, 255, 0.08);
}

.engine-link.active {
  color: #ffffff;
  background: var(--accent-primary);
  box-shadow: 0 0 8px var(--accent-glow);
}

.github-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s ease, opacity 0.2s ease, transform 0.2s ease;
  flex-shrink: 0;
  opacity: 0.75;
}

.github-link svg {
  width: 18px;
  height: 18px;
  display: block;
}

.github-link:hover {
  color: var(--text-main);
  opacity: 1;
  transform: translateY(-1px);
}

.book-info {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.book-title {
  font-size: 0.95rem;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 480px;
}

.book-subtitle {
  font-size: 0.75rem;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 480px;
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.45rem 0.75rem;
  border-radius: 8px;
  background: var(--bg-surface);
  color: var(--text-main);
  border: 1px solid var(--border-glass);
  cursor: pointer;
  font-family: var(--font-main);
  font-size: 0.85rem;
  font-weight: 500;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.icon-btn:hover {
  background: var(--bg-glass-hover);
  border-color: var(--border-glass-bright);
  transform: translateY(-1px);
}

.icon-btn.active {
  border-color: var(--accent-primary);
  box-shadow: 0 0 12px var(--accent-glow);
}

.icon-btn .icon {
  font-size: 1rem;
}

/* Main Viewport Stage */
.viewport-stage {
  flex: 1;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

.book-container {
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}





/* Side Navigation Arrows */
.side-nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 48px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--bg-glass);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border-glass);
  color: var(--text-main);
  border-radius: 12px;
  cursor: pointer;
  z-index: 30;
  transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.side-nav-btn.prev {
  left: 1.5rem;
}

.side-nav-btn.next {
  right: 1.5rem;
}

.side-nav-btn:hover:not(:disabled) {
  background: var(--bg-glass-hover);
  border-color: var(--border-glass-bright);
  transform: translateY(-50%) scale(1.08);
  box-shadow: var(--shadow-elevated);
}

.side-nav-btn:disabled {
  opacity: 0.25;
  cursor: not-allowed;
  transform: translateY(-50%) scale(0.95);
}

/* Hint Badge */
.flip-hint-badge {
  position: absolute;
  bottom: 1.25rem;
  padding: 0.4rem 0.9rem;
  background: var(--bg-glass);
  backdrop-filter: blur(8px);
  border: 1px solid var(--border-glass);
  border-radius: 20px;
  font-size: 0.75rem;
  color: var(--text-muted);
  pointer-events: none;
  z-index: 10;
  animation: fadeInOut 6s ease forwards;
}

@keyframes fadeInOut {
  0% { opacity: 0; transform: translateY(10px); }
  15% { opacity: 1; transform: translateY(0); }
  80% { opacity: 1; transform: translateY(0); }
  100% { opacity: 0; transform: translateY(10px); }
}

/* Footer & Controls */
.app-footer {
  display: flex;
  flex-direction: column;
  background: var(--bg-glass);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-top: 1px solid var(--border-glass);
  z-index: 50;
}

.timeline-container {
  width: 100%;
  padding: 0.4rem 1.5rem 0;
}

.timeline-track {
  position: relative;
  width: 100%;
  height: 6px;
  background: rgba(255, 255, 255, 0.08);
  border-radius: 3px;
  overflow: visible;
}

.timeline-fill {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  width: 0%;
  background: var(--accent-gradient);
  border-radius: 3px;
  pointer-events: none;
  transition: width 0.15s ease-out;
}

.timeline-slider {
  position: absolute;
  top: -6px;
  left: 0;
  width: 100%;
  height: 18px;
  margin: 0;
  opacity: 0;
  cursor: pointer;
  z-index: 5;
}

.footer-toolbar {
  height: 52px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1.5rem;
}

.toolbar-left, .toolbar-right, .toolbar-center {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.page-indicator-box {
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text-main);
}

.page-direct-jump {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.page-number-input {
  width: 48px;
  background: var(--bg-surface);
  border: 1px solid var(--border-glass);
  color: var(--text-main);
  text-align: center;
  padding: 0.25rem;
  border-radius: 6px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  outline: none;
}

.page-number-input:focus {
  border-color: var(--accent-primary);
  box-shadow: 0 0 8px var(--accent-glow);
}



/* Responsive adjustments */
@media (max-width: 768px) {
  .app-header {
    padding: 0 0.75rem;
  }
  .btn-text, .theme-picker-wrapper {
    display: none;
  }
  .side-nav-btn {
    width: 38px;
    height: 52px;
  }
  .side-nav-btn.prev { left: 0.5rem; }
  .side-nav-btn.next { right: 0.5rem; }
  .footer-toolbar {
    padding: 0 0.75rem;
  }
}