/* ============================================
   Book Reader - Reusable Styles
   Namespace: .book-*
   Dark theme default, mobile first
   ============================================ */

/* --- CSS Custom Properties (Theme) --- */
:root {
  --book-bg: #1a1a2e;
  --book-bg-page: #16213e;
  --book-text: #e0e0e0;
  --book-text-muted: #8a8a9a;
  --book-accent: #e2b97f;
  --book-accent-hover: #f0d0a0;
  --book-nav-bg: rgba(22, 33, 62, 0.95);
  --book-border: #2a2a4a;
  --book-shadow: rgba(0, 0, 0, 0.4);
  --book-controls-bg: rgba(22, 33, 62, 0.85);
  --book-page-num-bg: rgba(226, 185, 127, 0.15);
}

[data-theme="light"] {
  --book-bg: #f5f0e8;
  --book-bg-page: #fffdf8;
  --book-text: #2c2c2c;
  --book-text-muted: #6a6a6a;
  --book-accent: #8b6914;
  --book-accent-hover: #a07a1a;
  --book-nav-bg: rgba(255, 253, 248, 0.95);
  --book-border: #d4cfc4;
  --book-shadow: rgba(0, 0, 0, 0.12);
  --book-controls-bg: rgba(255, 253, 248, 0.85);
  --book-page-num-bg: rgba(139, 105, 20, 0.1);
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: 'Georgia', 'Times New Roman', serif;
  background: var(--book-bg);
  color: var(--book-text);
  min-height: 100dvh;
  overflow: hidden;
  transition: background 0.3s ease, color 0.3s ease;
}

/* --- Book Container --- */
.book {
  position: relative;
  width: 100%;
  height: 100dvh;
  overflow: hidden;
}

/* --- Book Page --- */
.book-page {
  position: absolute;
  inset: 0;
  display: none;
  flex-direction: column;
  background: var(--book-bg-page);
  transition: background 0.3s ease;
}

.book-page.active {
  display: flex;
}

/* --- Cover Page --- */
.book-page.book-cover {
  justify-content: center;
  align-items: center;
  text-align: center;
  padding: 2rem;
}

.book-cover-content {
  max-width: 90%;
}

.book-title {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--book-accent);
  margin-bottom: 0.5rem;
  letter-spacing: 0.05em;
  line-height: 1.2;
}

.book-subtitle {
  font-size: 1.1rem;
  color: var(--book-text-muted);
  font-style: italic;
  margin-bottom: 2rem;
}

.book-cover-start {
  display: inline-block;
  padding: 0.75rem 2rem;
  background: var(--book-accent);
  color: var(--book-bg);
  border: none;
  border-radius: 4px;
  font-family: inherit;
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.2s ease;
}

.book-cover-start:hover {
  background: var(--book-accent-hover);
}

/* --- Image Container --- */
.book-image {
  flex: 1 1 50%;
  min-height: 0;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  background: #000;
}

.book-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

/* --- Text Container --- */
.book-text {
  flex: 1 1 50%;
  padding: 1.5rem;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.book-text h2 {
  font-size: 1.4rem;
  color: var(--book-accent);
  margin-bottom: 0.75rem;
  line-height: 1.3;
}

.book-text p {
  font-size: 1rem;
  line-height: 1.7;
  margin-bottom: 0.75rem;
  color: var(--book-text);
}

.book-text p:last-child {
  margin-bottom: 0;
}

/* --- Navigation --- */
.book-nav {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.6rem 1rem;
  background: var(--book-nav-bg);
  backdrop-filter: blur(8px);
  border-top: 1px solid var(--book-border);
  z-index: 10;
}

.book-nav-btn {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.5rem 1rem;
  background: transparent;
  color: var(--book-accent);
  border: 1px solid var(--book-accent);
  border-radius: 4px;
  font-family: inherit;
  font-size: 0.85rem;
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease;
  min-width: 80px;
  justify-content: center;
}

.book-nav-btn:hover:not(:disabled) {
  background: var(--book-accent);
  color: var(--book-bg);
}

.book-nav-btn:disabled {
  opacity: 0.3;
  cursor: not-allowed;
}

.book-nav-btn.invisible {
  visibility: hidden;
}

.book-page-indicator {
  font-size: 0.85rem;
  color: var(--book-text-muted);
  font-variant-numeric: tabular-nums;
}

/* --- Page Number Badge --- */
.book-page-number {
  position: absolute;
  top: 0.75rem;
  right: 0.75rem;
  width: 2rem;
  height: 2rem;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--book-page-num-bg);
  color: var(--book-accent);
  border-radius: 50%;
  font-size: 0.8rem;
  font-weight: 600;
  z-index: 5;
  backdrop-filter: blur(4px);
}

/* --- Back Link --- */
.book-back-link {
  position: absolute;
  top: 0.75rem;
  left: 0.75rem;
  font-size: 0.85rem;
  color: var(--book-text-muted);
  text-decoration: none;
  background: var(--book-controls-bg);
  padding: 0.3rem 0.75rem;
  border-radius: 1rem;
  border: 1px solid var(--book-border);
  z-index: 10;
  backdrop-filter: blur(4px);
  transition: color 0.2s ease, border-color 0.2s ease;
}
.book-back-link:hover {
  color: var(--book-accent);
  border-color: var(--book-accent);
}

/* --- Controls (Theme + Fullscreen) --- */
.book-controls {
  position: absolute;
  top: 0.75rem;
  right: 0.75rem;
  display: flex;
  gap: 0.5rem;
  z-index: 10;
}

.book-control-btn {
  width: 2.2rem;
  height: 2.2rem;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--book-controls-bg);
  color: var(--book-text);
  border: 1px solid var(--book-border);
  border-radius: 50%;
  cursor: pointer;
  font-size: 1rem;
  backdrop-filter: blur(4px);
  transition: background 0.2s ease, border-color 0.2s ease;
}

.book-control-btn:hover {
  border-color: var(--book-accent);
  color: var(--book-accent);
}

/* Theme toggle icon swap */
.book-theme-btn .icon-light { display: inline; }
.book-theme-btn .icon-dark { display: none; }
[data-theme="light"] .book-theme-btn .icon-light { display: none; }
[data-theme="light"] .book-theme-btn .icon-dark { display: inline; }

/* Fullscreen icon swap */
.book-fullscreen-btn .icon-enter { display: inline; }
.book-fullscreen-btn .icon-exit { display: none; }
.book.is-fullscreen .book-fullscreen-btn .icon-enter { display: none; }
.book.is-fullscreen .book-fullscreen-btn .icon-exit { display: inline; }

/* --- Scroll Indicator (animated hairline) --- */
.book-text::-webkit-scrollbar {
  width: 2px;
}

.book-text::-webkit-scrollbar-track {
  background: transparent;
}

.book-text::-webkit-scrollbar-thumb {
  background: var(--book-accent);
  border-radius: 1px;
}

.book-scroll-line {
  position: absolute;
  right: 4px;
  top: 3.5rem;
  bottom: 3.5rem;
  width: 1px;
  background: var(--book-border);
  z-index: 5;
  overflow: hidden;
  opacity: 0;
  transition: opacity 0.3s ease;
  pointer-events: none;
}

.book-page.has-scroll .book-scroll-line {
  opacity: 1;
}

.book-scroll-line::after {
  content: '';
  position: absolute;
  top: -30%;
  left: 0;
  width: 100%;
  height: 30%;
  background: linear-gradient(to bottom, transparent, var(--book-accent), transparent);
  animation: scrollStreak 2.5s ease-in-out infinite;
}

@keyframes scrollStreak {
  0% { top: -30%; }
  100% { top: 100%; }
}

/* --- Touch Areas (invisible prev/next tap zones) --- */
.book-tap-prev,
.book-tap-next {
  position: absolute;
  top: 0;
  bottom: 3rem;
  width: 20%;
  z-index: 4;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.book-tap-prev { left: 0; }
.book-tap-next { right: 0; }

/* --- Page Transition --- */
.book-page {
  opacity: 0;
}

.book-page.active {
  opacity: 1;
  animation: bookFadeIn 0.35s ease-out;
}

@keyframes bookFadeIn {
  from { opacity: 0; transform: translateX(8px); }
  to { opacity: 1; transform: translateX(0); }
}

/* ============================================
   Landscape / Tablet+ (768px+)
   Two-column: image left, text right
   ============================================ */
@media (min-width: 768px) {
  .book-page:not(.book-cover) {
    flex-direction: row;
  }

  .book-image {
    flex: 0 0 55%;
    max-width: 55%;
    height: 100%;
  }

  .book-image img {
    object-fit: contain;
    object-position: center;
  }

  .book-text {
    flex: 1;
    padding: 2rem 2.5rem 3.5rem;
    overflow-y: auto;
  }

  .book-text h2 {
    font-size: 1.5rem;
    margin-bottom: 0.75rem;
  }

  .book-text p {
    font-size: 1.05rem;
    line-height: 1.8;
    margin-bottom: 1rem;
  }

  .book-title {
    font-size: 3.5rem;
  }

  .book-subtitle {
    font-size: 1.3rem;
  }

  .book-page-number {
    top: 1rem;
    right: 4rem;
    width: 2.4rem;
    height: 2.4rem;
    font-size: 0.9rem;
  }

  .book-scroll-line {
    right: 8px;
  }
}

/* ============================================
   Small phones (< 400px)
   ============================================ */
@media (max-width: 399px) {
  .book-text {
    padding: 1rem;
  }

  .book-text h2 {
    font-size: 1.2rem;
  }

  .book-text p {
    font-size: 0.9rem;
  }

  .book-title {
    font-size: 1.8rem;
  }

  .book-nav-btn {
    padding: 0.4rem 0.7rem;
    font-size: 0.8rem;
    min-width: 60px;
  }
}

/* ============================================
   Fullscreen adjustments
   ============================================ */
.book:-webkit-full-screen {
  width: 100vw;
  height: 100vh;
}

.book:fullscreen {
  width: 100vw;
  height: 100vh;
}