:root {
  --bg: #ececec;
  --panel: #ffffff;
  --line: #d9dde3;
  --text: #222;
  --muted: #6f7782;
  --accent: #5167d8;
  --accent-soft: #eef1ff;
  --shadow: 0 12px 36px rgba(15, 23, 42, 0.08);
  --radius: 18px;
  --sidebar-width: 290px;
}
* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: Arial, "Apple SD Gothic Neo", "Malgun Gothic", sans-serif;
  background: var(--bg);
  color: var(--text);
}
button, a { font: inherit; }
button { cursor: pointer; }
img { max-width: 100%; display: block; }
.ebook-app {
  display: grid;
  grid-template-columns: var(--sidebar-width) 1fr;
  height: 100vh;
  overflow: hidden;
}
.sidebar {
  background: #f8f9fb;
  border-right: 1px solid var(--line);
  padding: 20px 16px 16px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  overflow: hidden;
}
.sidebar-header h1 {
  margin: 0 0 6px;
  font-size: 18px;
}
.book-subtitle {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
}
.sidebar-tabs {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}
.tab-btn, .mode-btn, .tool-btn, .download-btn, .icon-btn {
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 12px;
  color: var(--text);
  transition: .2s ease;
}
.tab-btn, .mode-btn {
  padding: 10px 12px;
  font-weight: 700;
}
.tab-btn.active, .mode-btn.active {
  border-color: var(--accent);
  background: var(--accent-soft);
  color: var(--accent);
}
.tab-panel {
  display: none;
  min-height: 0;
  overflow: auto;
  padding-right: 4px;
}
.tab-panel.active { display: block; }
.thumb-list, .toc-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.thumb-item, .toc-item {
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 14px;
  padding: 10px;
  display: grid;
  gap: 8px;
  transition: .2s ease;
}
.thumb-item { grid-template-columns: 84px 1fr; align-items: center; }
.thumb-item:hover, .toc-item:hover,
.thumb-item.active, .toc-item.active {
  border-color: var(--accent);
  background: var(--accent-soft);
}
.thumb-item img {
  width: 84px;
  aspect-ratio: 3 / 4;
  object-fit: cover;
  border-radius: 8px;
  border: 1px solid #dfe3ea;
  background: #fff;
}
.thumb-meta, .toc-meta { min-width: 0; }
.page-no {
  color: var(--accent);
  font-size: 12px;
  font-weight: 700;
  margin-bottom: 4px;
}
.page-title, .toc-title {
  font-size: 14px;
  font-weight: 700;
  line-height: 1.35;
}
.page-desc, .toc-desc {
  margin-top: 4px;
  color: var(--muted);
  font-size: 12px;
  line-height: 1.45;
}
.viewer-shell {
  display: grid;
  grid-template-rows: auto 1fr auto;
  min-width: 0;
}
.topbar, .toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 18px;
  background: rgba(255,255,255,.9);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.toolbar {
  border-top: 1px solid var(--line);
  border-bottom: 0;
}
.topbar-left, .topbar-right, .toolbar-left, .toolbar-right {
  display: flex;
  align-items: center;
  gap: 10px;
}
.viewer-title { font-weight: 700; }
.icon-btn {
  width: 40px;
  height: 40px;
  font-size: 20px;
}
.mode-switch {
  display: flex;
  gap: 8px;
}
.download-btn, .tool-btn {
  padding: 10px 14px;
  text-decoration: none;
}
.download-btn:hover, .tool-btn:hover, .icon-btn:hover, .tab-btn:hover, .mode-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 18px rgba(15, 23, 42, 0.06);
}
.viewer-panel {
  min-height: 0;
  display: grid;
  grid-template-columns: 56px minmax(0, 1fr) 56px;
  align-items: stretch;
  padding: 20px 16px;
  gap: 14px;
}
.nav-arrow {
  border: 0;
  border-radius: 16px;
  background: rgba(255,255,255,.82);
  box-shadow: var(--shadow);
  color: #666;
  font-size: 42px;
  display: grid;
  place-items: center;
  align-self: center;
  width: 56px;
  height: 88px;
}
.stage-wrap {
  min-width: 0;
  min-height: 0;
  position: relative;
  display: grid;
}
.flip-stage, .scroll-stage {
  display: none;
  min-height: 0;
}
.flip-stage.active, .scroll-stage.active { display: grid; }
.flip-stage {
  place-items: center;
}
.page-card {
  width: min(100%, 900px);
  height: 100%;
  display: grid;
  place-items: center;
}
.page-card img {
  max-height: calc(100vh - 210px);
  width: auto;
  max-width: 100%;
  object-fit: contain;
  border-radius: 10px;
  background: #fff;
  box-shadow: 0 14px 40px rgba(0,0,0,.14);
  border: 1px solid #d8dde6;
  transition: transform .26s ease, opacity .26s ease;
}
.page-card img.turning {
  transform: translateX(14px) scale(.985);
  opacity: .68;
}
.scroll-stage {
  overflow: auto;
  padding: 12px 18px 28px;
  scroll-behavior: smooth;
}
.scroll-inner {
  width: min(100%, 960px);
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.scroll-page {
  background: #fff;
  padding: 10px;
  border-radius: 12px;
  box-shadow: 0 14px 40px rgba(0,0,0,.12);
  border: 1px solid #d8dde6;
}
.scroll-page img {
  width: 100%;
  height: auto;
  border-radius: 8px;
}
.scroll-page-label {
  font-size: 12px;
  color: var(--muted);
  margin-bottom: 8px;
}
.page-indicator {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 18px;
  font-weight: 700;
}
.slash { color: var(--muted); }
body.sidebar-collapsed .ebook-app {
  grid-template-columns: 0 1fr;
}
body.sidebar-collapsed .sidebar {
  padding: 0;
  border-right: 0;
  overflow: hidden;
}
@media (max-width: 1024px) {
  .ebook-app { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    width: min(86vw, 320px);
    z-index: 40;
    box-shadow: 20px 0 50px rgba(0,0,0,.18);
    transform: translateX(-100%);
    transition: transform .25s ease;
  }
  body.sidebar-open .sidebar { transform: translateX(0); }
  .viewer-panel { grid-template-columns: 44px minmax(0,1fr) 44px; padding: 14px 10px; }
  .nav-arrow { width: 44px; height: 72px; font-size: 32px; }
  .topbar, .toolbar { padding: 12px; }
}
@media (max-width: 680px) {
  .topbar, .toolbar {
    flex-wrap: wrap;
  }
  .topbar-right, .toolbar-right, .toolbar-left {
    width: 100%;
    justify-content: center;
  }
  .viewer-panel {
    grid-template-columns: 1fr;
  }
  .nav-arrow {
    position: fixed;
    bottom: 82px;
    z-index: 30;
    background: rgba(255,255,255,.92);
  }
  .nav-arrow.left { left: 10px; }
  .nav-arrow.right { right: 10px; }
}


.logo-mark {
  display:inline-flex; align-items:center; justify-content:center;
  min-width:88px; height:40px; padding:0 14px; border-radius:12px;
  border:1px solid var(--line); background:#fff; font-weight:800; letter-spacing:.08em;
}
.topbar-left { min-width: 120px; }
.viewer-panel {
  min-height: 0;
  display: grid;
  grid-template-columns: 56px minmax(0, 1fr) 56px;
  align-items: stretch;
  padding: 20px 16px;
  gap: 14px;
}
.spread-card {
  width: min(100%, 980px);
  height: 100%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 18px;
  align-items: center;
}
.spread-page {
  display:grid; place-items:center; min-width:0; min-height:0;
}
.spread-page img {
  max-height: calc(100vh - 210px);
  width: 100%;
  max-width: 100%;
  object-fit: contain;
  border-radius: 10px;
  background: #fff;
  box-shadow: 0 14px 40px rgba(0,0,0,.14);
  border: 1px solid #d8dde6;
  transition: transform .26s ease, opacity .26s ease;
}
.spread-page img.turning-left { transform: translateX(-10px) scale(.988); opacity: .75; }
.spread-page img.turning-right { transform: translateX(10px) scale(.988); opacity: .75; }
.spread-page.is-empty { visibility:hidden; }
.mode-switch, .mode-btn, .scroll-stage, #scrollStage, .viewer-title, .icon-btn { display:none !important; }
@media (max-width: 900px) {
  .spread-card { grid-template-columns: 1fr; gap: 12px; width:min(100%,560px); }
  .spread-page.right { display:none; }
}