:root,
:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0f0f12;
  --bg-elevated: #1a1a20;
  --bg-hover: #24242c;
  --text: #e8e8ee;
  --text-muted: #8a8a95;
  --accent: #3F4389;
  --accent-soft: #5a5ea6;
  --border: #2a2a33;
  --success: #4ade80;
  --pivot-line: #2a2a33;
  --pivot-color: #A12A2C;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
  --radius: 12px;
  --transition: 150ms ease;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, sans-serif;
}

:root[data-theme="light"] {
  color-scheme: light;
  --bg: #f7f7f9;
  --bg-elevated: #ffffff;
  --bg-hover: #eeeef2;
  --text: #1a1a1f;
  --text-muted: #666672;
  --border: #e0e0e6;
  --pivot-line: #d8d8de;
  --pivot-color: #A12A2C;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
}

/* Soft, warm pastel — cream page with a dusty-lavender accent and rose pivot. */
:root[data-theme="pastel-light"] {
  color-scheme: light;
  --bg: #FAF3EE;
  --bg-elevated: #FFFBF6;
  --bg-hover: #F2E6DA;
  --text: #3D3748;
  --text-muted: #8B8197;
  --accent: #8D95D6;
  --accent-soft: #AEB5E5;
  --border: #EADFD3;
  --pivot-line: #DCCFC2;
  --pivot-color: #C9646B;
  --shadow: 0 2px 14px rgba(80, 60, 80, 0.10);
}

/* Muted plum/dusk with a soft lavender accent and pastel rose pivot. */
:root[data-theme="pastel-dark"] {
  color-scheme: dark;
  --bg: #221C30;
  --bg-elevated: #2D263F;
  --bg-hover: #383051;
  --text: #EEE5DB;
  --text-muted: #A69CB0;
  --accent: #B7A9E0;
  --accent-soft: #CAC0EA;
  --border: #3A334F;
  --pivot-line: #3A334F;
  --pivot-color: #E89BA0;
  --shadow: 0 4px 28px rgba(0, 0, 0, 0.45);
}

* { box-sizing: border-box; }

/* The HTML `hidden` attribute should always win over CSS display rules. */
[hidden] { display: none !important; }

/* ---------- Theme selector dropdown ---------- */
.theme-select {
  position: relative;
}
.theme-panel {
  position: absolute;
  top: calc(100% + 0.35rem);
  right: 0;
  min-width: 160px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 0.3rem;
  box-shadow: var(--shadow);
  z-index: 200;
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
}
.theme-panel[hidden] { display: none; }
.theme-panel > button {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  padding: 0.5rem 0.7rem;
  background: transparent;
  border: none;
  color: var(--text);
  cursor: pointer;
  border-radius: 6px;
  font-size: 0.88rem;
  text-align: left;
  font-family: inherit;
  white-space: nowrap;
}
.theme-panel > button:hover {
  background: var(--bg-hover);
}
.theme-panel > button.active {
  color: var(--accent);
  font-weight: 600;
}
.theme-swatch {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  flex-shrink: 0;
  border: 1px solid color-mix(in srgb, var(--text) 20%, transparent);
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  height: 100%;
  overflow: hidden;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-size: 16px;
  line-height: 1.5;
}

#app {
  height: 100dvh;
  width: 100%;
  position: relative;
}

.view {
  position: absolute;
  inset: 0;
  display: none;
  flex-direction: column;
  overflow: hidden;
}
.view.active { display: flex; }

/* ---------- Library ---------- */

.lib-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.5rem;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  flex-wrap: wrap;
}

.lib-brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  min-width: 0;
}
.lib-logo {
  width: 28px;
  height: 28px;
  display: block;
  flex-shrink: 0;
}

.lib-header h1 {
  margin: 0;
  font-size: 1.3rem;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.book-search {
  flex: 1 1 220px;
  max-width: 360px;
  padding: 0.5rem 0.9rem;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-size: 0.92rem;
  font-family: inherit;
  outline: none;
  transition: border-color var(--transition), box-shadow var(--transition);
  min-width: 0;
}
.book-search:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 22%, transparent);
}
.book-search::placeholder { color: var(--text-muted); }
.book-search::-webkit-search-cancel-button { cursor: pointer; }

.lib-actions { display: flex; gap: 0.5rem; flex-shrink: 0; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.55rem 1rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text);
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
  transition: background var(--transition), border-color var(--transition);
  user-select: none;
}
.btn:hover { background: var(--bg-hover); }
.btn.primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.btn.primary:hover {
  background: var(--accent-soft);
  border-color: var(--accent-soft);
}

.upload-status {
  margin: 0.75rem 1.5rem 0;
  padding: 0.75rem 1rem;
  border-radius: var(--radius);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  font-size: 0.9rem;
  color: var(--text-muted);
}
.upload-status.error { border-color: var(--accent); color: var(--accent); }

.book-list {
  list-style: none;
  margin: 0;
  padding: 1rem 1.5rem 2rem;
  overflow-y: auto;
  flex: 1;
}

.book-item {
  display: flex;
  align-items: stretch;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 0.75rem;
  overflow: hidden;
  transition: border-color var(--transition);
}
.book-item:hover { border-color: var(--accent); }

.book-main {
  flex: 1;
  display: flex;
  gap: 1rem;
  align-items: stretch;
  text-align: left;
  padding: 0.9rem 1.15rem;
  background: transparent;
  color: var(--text);
  border: none;
  cursor: pointer;
  font: inherit;
  min-width: 0;
}
.book-main:hover { background: var(--bg-hover); }

.book-cover {
  width: 48px;
  height: 72px;
  flex-shrink: 0;
  border-radius: 4px;
  overflow: hidden;
  background: var(--bg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  font-size: 1.6rem;
  font-weight: 700;
}
.book-cover img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}
.book-cover-empty {
  border: 1px dashed var(--border);
}

.book-info {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.book-title {
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 0.15rem;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.book-author {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 0.4rem;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.book-meta {
  display: flex;
  gap: 0.75rem;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 0.45rem;
}

.book-progressbar {
  height: 3px;
  background: var(--border);
  border-radius: 2px;
  overflow: hidden;
}
.book-progressbar-fill {
  height: 100%;
  background: var(--accent);
  width: 0%;
  transition: width var(--transition);
}

.book-delete {
  flex-shrink: 0;
  background: transparent;
  border: none;
  border-left: 1px solid var(--border);
  color: var(--text-muted);
  padding: 0 1rem;
  cursor: pointer;
  transition: color var(--transition), background var(--transition);
}
.book-delete:hover {
  color: var(--accent);
  background: var(--bg-hover);
}

.empty-state {
  padding: 1.25rem 1.5rem 1.5rem;
  text-align: center;
  color: var(--text-muted);
}
.empty-state[hidden] { display: none; }
.empty-state h2 {
  color: var(--text);
  margin: 0 0 0.4rem;
  font-size: 1.05rem;
  font-weight: 600;
}
.empty-state p { margin: 0.15rem 0; font-size: 0.92rem; }
.empty-state .muted { font-size: 0.82rem; opacity: 0.7; }

.drop-overlay {
  position: fixed;
  top: 1rem;
  right: 1rem;
  bottom: 1rem;
  width: min(240px, 30vw);
  z-index: 999;
  display: none;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  background: color-mix(in srgb, var(--accent) 10%, transparent);
  border: 2px dashed var(--accent);
  border-radius: var(--radius);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
}
.drop-overlay.active { display: flex; }

.drop-overlay-inner {
  padding: 1rem 1.25rem;
  color: var(--text);
  text-align: center;
}
.drop-overlay-title {
  font-size: 1rem;
  font-weight: 600;
}
.drop-overlay-formats {
  margin-top: 0.35rem;
  font-size: 0.78rem;
  font-weight: 500;
  color: var(--text-muted);
  letter-spacing: 0.02em;
}

@media (max-width: 640px) {
  .drop-overlay {
    top: auto;
    right: 0.75rem;
    left: 0.75rem;
    bottom: 0.75rem;
    width: auto;
    height: 4rem;
  }
}

/* ---------- Reader ---------- */

.reader-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
  contain: layout style;
}
.reader-title {
  flex: 1;
  font-size: 0.95rem;
  font-weight: 500;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  color: var(--text-muted);
}
.reader-progress {
  font-variant-numeric: tabular-nums;
  font-size: 0.85rem;
  color: var(--text-muted);
  min-width: 3ch;
  text-align: right;
}

.icon-btn {
  background: transparent;
  color: var(--text);
  border: none;
  font-size: 1.1rem;
  padding: 0.5rem 0.75rem;
  cursor: pointer;
  border-radius: 8px;
  transition: background var(--transition);
  font-family: var(--sans);
}
.icon-btn:hover { background: var(--bg-hover); }
.icon-btn.big {
  font-size: 1.75rem;
  padding: 0.75rem 1.25rem;
  background: var(--accent);
  color: #fff;
  border-radius: 50%;
  width: 4rem;
  height: 4rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}
.icon-btn.big:hover { background: var(--accent-soft); }

.reader-stage {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
  overflow: hidden;
  padding: 1rem;
}

.word-display {
  font-family: var(--mono);
  /* Per-breakpoint size so even 18-char words don't clip on narrow flex slots
     — the overall clamp shrinks below `.word-display` media override. */
  font-size: clamp(2rem, 8vw, 4.5rem);
  font-weight: 500;
  letter-spacing: -0.01em;
  display: flex;
  align-items: baseline;
  line-height: 1.1;
  white-space: pre;
  /* The pivot column is at the center; before right-aligns, after left-aligns */
  width: 100%;
  justify-content: center;
  position: relative;
  z-index: 10;
  /* Backdrop fades to transparent at the horizontal edges so the cover
     (left) and text preview (right) remain visible past the flashing word. */
  background: linear-gradient(
    to right,
    transparent 0%,
    var(--bg) 22%,
    var(--bg) 78%,
    transparent 100%
  );
  padding: 0.4rem 0;
  /* Critical: isolate layout so per-tick textContent updates don't dirty
     the entire document's layout tree. */
  contain: layout style;
}

.word-before,
.word-after {
  flex: 1 0 0;
  min-width: 0;
  white-space: pre;
  overflow: hidden;
  display: inline-block;
}
.word-before { text-align: right; direction: ltr; }
.word-after { text-align: left; }

.word-pivot {
  color: var(--pivot-color);
  flex: 0 0 auto;
}

.guide-line {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -100%);
  width: 1px;
  height: 1.5rem;
  background: var(--pivot-line);
  pointer-events: none;
}
/* Second guide mark below */
.guide-line::after {
  content: "";
  position: absolute;
  left: 0;
  top: calc(100% + 2.2rem);
  width: 1px;
  height: 1.5rem;
  background: var(--pivot-line);
}

/* Linear progress bar below the reader header */
.progress-bar {
  height: 3px;
  background: var(--border);
  flex-shrink: 0;
  contain: strict;
}
.progress-bar-fill {
  height: 100%;
  width: 0%;
  background: var(--accent);
  transition: width 120ms linear;
}

.reader-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  padding: 0.4rem 1rem;
  font-size: 0.78rem;
  color: var(--text-muted);
  flex-shrink: 0;
  font-variant-numeric: tabular-nums;
  contain: layout style;
}
.reader-stat {
  white-space: nowrap;
}
.reader-stat-label {
  opacity: 0.65;
}
.reader-stat-sep {
  opacity: 0.4;
}
#stat-read, #stat-left, #stat-total {
  color: var(--text);
}

/* Left-docked book cover: mirror layout to the text preview on the right,
   faded so it sits in the background behind the flashing word. */
.cover-side {
  position: absolute;
  left: 1rem;
  top: 1rem;
  bottom: 1rem;
  width: clamp(140px, 20vw, 400px);
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0.36;
  pointer-events: none;
  z-index: 1;
}
.cover-side img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  display: block;
}
/* Phone: shrink to a small thumbnail anchored to the top-left so it's
   visible without competing for horizontal space with the flashing word. */
@media (max-width: 640px) {
  .cover-side {
    left: 0.5rem;
    top: 0.5rem;
    bottom: auto;
    width: clamp(56px, 16vw, 96px);
    height: clamp(84px, 24vw, 144px);
    opacity: 0.32;
  }
}

/* Right-docked text preview column: fills the stage vertically,
   max 20vw wide. Uses native overflow-y scrolling so the browser
   renders a real scrollbar; scrollTop is driven from JS to keep
   the current word at the vertical center. */
.text-preview {
  position: absolute;
  right: 1rem;
  top: 1rem;
  bottom: 1rem;
  width: clamp(140px, 20vw, 400px);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow-y: auto;
  overflow-x: hidden;
  box-shadow: var(--shadow);
  z-index: 1;
  /* Bound layout work: any reflow inside the preview's 100K+ spans stops
     at this element and can't force a relayout of the outer document. */
  contain: layout style paint;
  /* scroll-behavior intentionally NOT smooth: at high WPM we set scrollTop
     once per tick, and smooth scrolling queues conflicting animations. */
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}
/* Phone: shrink and use a thinner scrollbar. The preview is still useful
   as an orientation aid on narrow screens; we just need to leave enough
   horizontal room for the flashing word. */
@media (max-width: 640px) {
  .text-preview {
    right: 0.5rem;
    top: 0.5rem;
    bottom: 0.5rem;
    width: clamp(100px, 26vw, 160px);
  }
  .text-preview-inner {
    padding: 0.45rem 0.6rem;
    font-size: 10px;
    line-height: 15px;
  }
  .text-preview::-webkit-scrollbar { width: 4px; }
}
.text-preview::-webkit-scrollbar {
  width: 8px;
}
.text-preview::-webkit-scrollbar-track {
  background: transparent;
}
.text-preview::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 4px;
}
.text-preview::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

.text-preview-inner {
  padding: 0.6rem 0.9rem;
  font-size: 11px;
  line-height: 17px;
  color: var(--text-muted);
  font-family: var(--sans);
}

/* Chunk container: each holds ~100 words and is individually skippable.
   `content-visibility: auto` lets Chrome bypass style/layout/paint entirely
   when the chunk isn't near the viewport, which shrinks per-frame work on
   a 100K-word book from O(all spans) to O(visible spans).
   `contain-intrinsic-size: auto 400px` is the placeholder size the browser
   reserves for skipped chunks; `auto` means "remember the real size after
   the first time it's rendered", so the scrollbar stays accurate. */
.preview-chunk {
  content-visibility: auto;
  contain-intrinsic-size: auto 400px;
}

.text-preview .preview-word {
  display: inline;
  white-space: normal;
  cursor: pointer;
}
.text-preview .preview-word:hover {
  background: var(--bg-hover);
  border-radius: 3px;
}
/* NOTE: keep this style PAINT-ONLY (color, text-shadow). Adding anything
   that changes layout (padding, font-weight, outline, border) would dirty
   layout on every class toggle, defeating the cached-offset hot path. */
.text-preview .preview-word.current {
  color: var(--accent);
  text-shadow: 0 0 1px var(--accent);
}



.reader-controls {
  padding: 1rem 1.5rem 1.5rem;
  border-top: 1px solid var(--border);
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  padding-bottom: max(1.5rem, env(safe-area-inset-bottom));
}

.control-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
}

.slider-row {
  flex-direction: column;
  gap: 0.4rem;
}

.slider-label {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-variant-numeric: tabular-nums;
}
.slider-label #wpm-value {
  color: var(--text);
  font-weight: 600;
}

#wpm-slider {
  width: 100%;
  max-width: 480px;
  accent-color: var(--accent);
  height: 2rem;
}

/* ---------- Mobile tweaks ---------- */

@media (max-width: 640px) {
  .reader-stage { padding: 0.5rem; }
  .word-display {
    font-size: clamp(1.35rem, 7vw, 2.75rem);
    padding: 0.3rem 0;
  }
}
@media (max-width: 520px) {
  .lib-header { padding: 1rem; }
  .book-list { padding: 0.75rem 1rem 1.5rem; }
  .reader-header { padding: 0.5rem 0.75rem; }
  .reader-controls { padding: 0.75rem 1rem 1.25rem; }
}

/* Disable pull-to-refresh and text selection in reader */
#reader-view {
  user-select: none;
  -webkit-user-select: none;
}