:root {
  --bg: #2a2a2c;
  --bg-deep: #141415;
  --ink: #f2f0ec;
  --ink-dim: #a9a6a0;
  --chrome: rgba(24, 24, 26, 0.82);
  --chrome-line: rgba(255, 255, 255, 0.08);
  --top: 56px;
  --bottom: 84px;
  --side: 72px;
  --ease: cubic-bezier(.2, .7, .2, 1);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  height: 100%;
  overflow: hidden;
  background: radial-gradient(ellipse at 50% 40%, var(--bg) 0%, var(--bg-deep) 100%);
  color: var(--ink);
  font: 14px/1.4 "Segoe UI", system-ui, -apple-system, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}

button, .btn {
  display: inline-grid;
  place-items: center;
  width: 40px;
  height: 40px;
  padding: 0;
  border: 0;
  border-radius: 10px;
  background: transparent;
  color: var(--ink);
  cursor: pointer;
  transition: background .15s, color .15s, opacity .15s;
}
button:hover, .btn:hover { background: rgba(255, 255, 255, 0.1); }
button.active { color: var(--accent); }
button:disabled { opacity: .3; cursor: default; background: transparent; }
svg { width: 20px; height: 20px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }

/* ---------- loader ---------- */
#loader {
  position: fixed; inset: 0; z-index: 100;
  display: grid; place-content: center; justify-items: center; gap: 18px;
  background: var(--bg-deep);
  transition: opacity .5s;
}
#loader.done { opacity: 0; pointer-events: none; }
.spinner {
  width: 38px; height: 38px; border-radius: 50%;
  border: 3px solid rgba(255, 255, 255, .12); border-top-color: var(--accent);
  animation: spin .9s linear infinite;
}
.loader-title { color: var(--ink-dim); letter-spacing: .08em; text-transform: uppercase; font-size: 12px; }
@keyframes spin { to { transform: rotate(360deg); } }

/* ---------- top bar ---------- */
.topbar {
  position: fixed; top: 0; left: 0; right: 0; height: var(--top);
  display: flex; align-items: center; padding: 0 20px;
  pointer-events: none;
}
.title { font-size: 13px; letter-spacing: .12em; text-transform: uppercase; color: var(--ink-dim); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }

/* ---------- stage & book ---------- */
#stage { position: fixed; top: var(--top); bottom: var(--bottom); left: var(--side); right: var(--side); }
#book-shift { position: absolute; inset: 0; transition: transform .6s var(--ease); }
#book { width: 100%; height: 100%; min-width: 0 !important; }
#book.stf__parent { touch-action: none; }
#book .stf__wrapper { position: absolute; inset: 0; }

.page { background: #fff; overflow: hidden; }
.page.blank { background: transparent; box-shadow: none !important; }
.page .pg {
  position: absolute; inset: 0;
  background-size: 100% 100%;
}
.page img { position: absolute; inset: 0; width: 100%; height: 100%; display: block; pointer-events: none; opacity: 0; transition: opacity .25s; }
.page img.loaded { opacity: 1; }

/* spine shading: darkens towards the fold like a real bound book */
.page .pg::after {
  content: ""; position: absolute; top: 0; bottom: 0; width: 14%; pointer-events: none; z-index: 2;
}
/* --spine is set from the book's finish (glossy / satin / matte) */
.page.--left .pg::after { right: 0; background: linear-gradient(to left, rgba(0,0,0,var(--spine, .22)), rgba(0,0,0,calc(var(--spine, .22) * .27)) 30%, transparent); }
.page.--right .pg::after { left: 0; background: linear-gradient(to right, rgba(0,0,0,var(--spine, .22)), rgba(0,0,0,calc(var(--spine, .22) * .27)) 30%, transparent); }
#book .stf__wrapper.--portrait .page .pg::after { display: none; }
.page.--left  { box-shadow: -6px 10px 28px rgba(0,0,0,.45); }
.page.--right { box-shadow:  6px 10px 28px rgba(0,0,0,.45); }

/* clickable areas from the PDF */
.pf-link { position: absolute; z-index: 3; cursor: pointer; border-radius: 2px; transition: background .2s, box-shadow .2s; }
.pf-link:hover { background: color-mix(in srgb, var(--accent) 22%, transparent); box-shadow: 0 0 0 1px color-mix(in srgb, var(--accent) 70%, transparent); }
.pf-link.large:hover { background: transparent; box-shadow: inset 0 0 0 2px color-mix(in srgb, var(--accent) 45%, transparent); }
body.flipping .pf-link { pointer-events: none; }
.hl { position: absolute; z-index: 2; background: rgba(255, 214, 0, .45); mix-blend-mode: multiply; border-radius: 2px; pointer-events: none; }

/* big side arrows */
.nav-arrow {
  position: absolute; top: 50%; width: 52px; height: 88px; margin-top: -44px;
  color: var(--ink-dim); border-radius: 12px;
}
.nav-arrow svg { width: 34px; height: 34px; stroke-width: 1.4; }
.nav-arrow.prev { left: calc(-1 * var(--side) + 10px); }
.nav-arrow.next { right: calc(-1 * var(--side) + 10px); }
.nav-arrow:hover { color: var(--ink); background: rgba(255, 255, 255, .06); }
.nav-arrow:disabled { visibility: hidden; }

/* ---------- toolbar ---------- */
.toolbar {
  position: fixed; left: 50%; bottom: 18px; transform: translateX(-50%); z-index: 20;
  display: flex; align-items: center; gap: 4px; padding: 6px;
  background: var(--chrome); border: 1px solid var(--chrome-line); border-radius: 14px;
  backdrop-filter: blur(14px); -webkit-backdrop-filter: blur(14px);
  box-shadow: 0 10px 30px rgba(0, 0, 0, .35);
}
/* blurring the live book behind the chrome on every animation frame drops frames, so pause it mid-flip */
body.flipping .toolbar, body.flipping #thumbs, body.flipping #panel {
  backdrop-filter: none; -webkit-backdrop-filter: none; background: rgba(24, 24, 26, .96);
}
.toolbar .group { display: flex; align-items: center; gap: 2px; }
.toolbar .group + .group { padding-left: 6px; margin-left: 4px; border-left: 1px solid var(--chrome-line); }
#page-form { display: flex; align-items: baseline; gap: 4px; padding: 0 6px; color: var(--ink-dim); font-variant-numeric: tabular-nums; }
#page-input {
  width: 62px; padding: 6px 4px; border: 1px solid transparent; border-radius: 8px;
  background: rgba(255, 255, 255, .06); color: var(--ink); font: inherit; text-align: center;
}
#page-input:focus { outline: none; border-color: var(--accent); }
#page-total { white-space: nowrap; }
#download[hidden] { display: none; }

/* ---------- side panel (contents / search) ---------- */
#panel {
  position: fixed; top: 0; bottom: 0; left: 0; width: min(360px, 88vw); z-index: 30;
  display: flex; flex-direction: column;
  background: var(--chrome); border-right: 1px solid var(--chrome-line);
  backdrop-filter: blur(18px); -webkit-backdrop-filter: blur(18px);
  transform: translateX(-102%); transition: transform .35s var(--ease);
  user-select: text;
}
#panel.open { transform: none; box-shadow: 20px 0 50px rgba(0, 0, 0, .4); }
.panel-tabs { display: flex; align-items: center; gap: 4px; padding: 12px 12px 0; border-bottom: 1px solid var(--chrome-line); }
.panel-tabs button[data-tab] {
  width: auto; height: 40px; padding: 0 14px; border-radius: 8px 8px 0 0;
  color: var(--ink-dim); font: inherit; letter-spacing: .04em; border-bottom: 2px solid transparent;
}
.panel-tabs button[data-tab].active { color: var(--ink); border-bottom-color: var(--accent); }
.panel-close { margin-left: auto; }
.panel-body { flex: 1; overflow-y: auto; padding: 12px; display: none; }
.panel-body.active { display: block; }

#toc-list, #search-results { list-style: none; margin: 0; padding: 0; }
#toc-list li, #search-results li {
  display: flex; gap: 12px; align-items: baseline; padding: 11px 12px; border-radius: 8px; cursor: pointer;
}
#toc-list li:hover, #search-results li:hover { background: rgba(255, 255, 255, .07); }
#toc-list li.current { color: var(--accent); }
#toc-list .t { flex: 1; font-size: 15px; }
#toc-list .lvl2 { padding-left: 28px; font-size: 13px; }
#toc-list .p, #search-results .p { color: var(--ink-dim); font-size: 12px; font-variant-numeric: tabular-nums; }
#search-results li { flex-direction: column; gap: 2px; }
#search-results .snip { color: var(--ink-dim); font-size: 13px; }
#search-results mark { background: none; color: var(--accent); font-weight: 600; }

#search-form { position: relative; margin-bottom: 10px; }
#search-form svg { position: absolute; left: 12px; top: 11px; width: 18px; height: 18px; color: var(--ink-dim); }
#search-input {
  width: 100%; padding: 10px 12px 10px 38px; border-radius: 10px; border: 1px solid var(--chrome-line);
  background: rgba(255, 255, 255, .06); color: var(--ink); font: inherit;
}
#search-input:focus { outline: none; border-color: var(--accent); }
#search-status { color: var(--ink-dim); font-size: 12px; padding: 2px 4px 8px; }

/* ---------- thumbnail strip ---------- */
#thumbs {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 15; height: 210px;
  background: var(--chrome); border-top: 1px solid var(--chrome-line);
  backdrop-filter: blur(18px); -webkit-backdrop-filter: blur(18px);
  transform: translateY(105%); transition: transform .35s var(--ease);
}
#thumbs.open { transform: none; }
body.thumbs-open #stage { bottom: 226px; }
.thumbs-track {
  display: flex; gap: 18px; height: 100%; padding: 18px 24px 84px; overflow-x: auto; overflow-y: hidden;
  scrollbar-width: thin; scrollbar-color: rgba(255,255,255,.2) transparent;
}
.thumb { flex: none; display: flex; flex-direction: column; align-items: center; gap: 6px; cursor: pointer; }
.thumb .imgs { display: flex; height: 100%; min-height: 0; box-shadow: 0 4px 14px rgba(0,0,0,.4); outline: 2px solid transparent; outline-offset: 3px; transition: outline-color .2s; }
.thumb img { height: 100%; display: block; background: #ddd; }
.thumb:hover .imgs { outline-color: rgba(255,255,255,.35); }
.thumb.current .imgs { outline-color: var(--accent); }
.thumb span { font-size: 11px; color: var(--ink-dim); }

/* ---------- zoom ---------- */
#zoom {
  position: fixed; inset: 0; z-index: 40; overflow: hidden;
  background: rgba(10, 10, 11, .96);
  opacity: 0; pointer-events: none; transition: opacity .25s;
  cursor: grab; touch-action: none;
}
#zoom.open { opacity: 1; pointer-events: auto; }
#zoom.dragging { cursor: grabbing; }
.zoom-canvas { position: absolute; left: 0; top: 0; display: flex; transform-origin: 0 0; will-change: transform; }
.zoom-canvas img { display: block; background: #fff; }
.zoom-controls {
  position: absolute; right: 18px; top: 18px; display: flex; gap: 4px; padding: 6px;
  background: var(--chrome); border: 1px solid var(--chrome-line); border-radius: 12px;
}

/* ---------- toast ---------- */
#toast {
  position: fixed; left: 50%; bottom: 96px; z-index: 50; transform: translate(-50%, 20px);
  padding: 10px 16px; border-radius: 10px; background: var(--chrome); border: 1px solid var(--chrome-line);
  opacity: 0; transition: opacity .25s, transform .25s; pointer-events: none;
}
#toast.show { opacity: 1; transform: translate(-50%, 0); }

/* ---------- small screens ---------- */
@media (max-width: 760px) {
  :root { --top: 44px; --bottom: 76px; --side: 8px; }
  .nav-arrow, .wide-only, [data-action="share"] { display: none; }
  .toolbar { bottom: 12px; padding: 4px; gap: 0; width: calc(100vw - 16px); justify-content: space-between; }
  .toolbar .group + .group { padding-left: 2px; margin-left: 2px; }
  .toolbar button, .toolbar .btn { width: 34px; height: 36px; }
  #page-form { padding: 0 2px; font-size: 13px; }
  #page-input { width: 48px; }
  .page.--left, .page.--right { box-shadow: 0 8px 24px rgba(0,0,0,.45); }
}