/*
  Scientific Ebook Prototype
  --------------------------
  Stable POC baseline styles.
  This stylesheet is intentionally organized by responsibility so future
  layout tuning can happen with minimal risk to the pagination model.
*/

/* ==========================================================================
   1. Design tokens
   ========================================================================== */
:root {
  --bg: #cfdced;
  --paper: #f7f9fc;
  --paper-edge: #e8eef5;
  --text: #182638; /* before #1f3146x */
  --muted: #5d728b;
  --accent: #3f6f9f;
  --shadow: 0 16px 34px rgba(32, 54, 82, 0.10);

  --toolbar-height: 48px;
  --page-width: 780px;
  --page-height: 1080px;
  --page-gap: 26px;
  --page-padding-x: 36px;
  --page-padding-y: 40px;
  --page-scale: 1;
  --page-nav-gutter-left: 36px;
  --page-nav-gutter-right: 36px;
  --page-nav-button-width: 28px;
  --page-nav-gap: 5px;

  --font-ui: "Segoe UI", Roboto, Arial, sans-serif;
  --base-font-size: 15px;
  --base-line-height: 1.5;
  --p-size: 1rem;
  --h4-size: 1rem;
  --h3-size: 1.15rem;
  --h2-size: 1.3rem;
  --h1-size: 1.5rem;
  --content-max-image-height: 760px;/* 540px */
}

/* ==========================================================================
   2. Global reset and base document setup
   ========================================================================== */
* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  width: 100%;
  height: 100%;
  min-height: 100%;
  overflow: hidden;
}

html {
  font-size: var(--base-font-size);
}

body {
  font-family: var(--font-ui);
  color: var(--text);
  line-height: var(--base-line-height);
  background:
    radial-gradient(circle at top, rgba(255, 255, 255, 0.56), transparent 42%),
    linear-gradient(180deg, rgba(230, 239, 248, 1) 0%, rgba(207, 220, 237, 1) 100%);
}

button,
input,
select,
textarea {
  font: inherit;
}

/* ==========================================================================
   3. App header / toolbar
   ========================================================================== */
.toolbar {
  --toolbar-logical-width: calc(100vw - 32px);
  --toolbar-inline-start: 16px;
  height: var(--toolbar-height);
  min-height: 0;
  width: var(--toolbar-logical-width);
  margin-left: var(--toolbar-inline-start);
  margin-right: 0;
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: 14px;
  padding: 6px 16px;
  background: rgba(237, 243, 249, 0.94);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(63, 111, 159, 0.14);
  border-bottom-left-radius: 6px;
  border-bottom-right-radius: 6px;
  position: sticky;
  top: 0;
  z-index: 20;
}

.toolbar__group {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.toolbar__group--left,
.toolbar__group--right {
  flex-wrap: nowrap;
}

.toolbar__spacer {
  min-width: 0;
}

.tool-btn {
  width: 28px;
  height: 28px;
  display: inline-grid;
  place-items: center;
  padding: 0;
  border: 1px solid rgba(63, 111, 159, 0.18);
  background: rgba(248, 251, 255, 0.96);
  color: #4d627b;
  border-radius: 4px;
  cursor: pointer;
  transition: transform 0.12s ease, box-shadow 0.15s ease, border-color 0.15s ease, background-color 0.15s ease, color 0.15s ease, opacity 0.15s ease;
  box-shadow: 0 1px 2px rgba(20, 38, 63, 0.05);
}

.tool-btn svg {
  width: 15px;
  height: 15px;
  stroke: currentColor;
  stroke-width: 1.4;
  fill: none;
  vector-effect: non-scaling-stroke;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.tool-btn:hover:not(:disabled) {
  transform: translateY(-1px);
  border-color: rgba(63, 111, 159, 0.3);
  box-shadow: 0 4px 10px rgba(20, 38, 63, 0.08);
  color: var(--accent);
}

.tool-btn:disabled {
  opacity: 0.42;
  cursor: default;
  transform: none;
  box-shadow: 0 1px 2px rgba(20, 38, 63, 0.04);
}

.tool-btn.is-active {
  background: rgba(63, 111, 159, 0.12);
  border-color: rgba(63, 111, 159, 0.3);
  color: #214f80;
  box-shadow: inset 0 0 0 1px rgba(63, 111, 159, 0.05);
}


.tool-btn--jump svg {
  width: 15px;
  height: 15px;
  stroke-width: 1.85;
}

.tool-indicator {
  height: 28px;
  display: inline-grid;
  place-items: center;
  border: 1px solid rgba(63, 111, 159, 0.18);
  background: rgba(248, 251, 255, 0.96);
  color: #4d627b;
  border-radius: 4px;
  box-shadow: 0 1px 2px rgba(20, 38, 63, 0.05);
  cursor: default;
  user-select: none;
}

.tool-indicator--zoom {
  min-width: 3rem;
  padding-inline: 0.45rem;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.page-indicator {
  min-width: 4.6rem;
  padding: 0.25rem 0.5rem;
  border: 1px solid rgba(63, 111, 159, 0.14);
  background: rgba(248, 251, 255, 0.88);
  border-radius: 4px;
  color: #566b84;
  font-size: 0.78rem;
  font-weight: 600;
  text-align: center;
  letter-spacing: 0.01em;
}

.find-panel {
  position: fixed;
  left: 1rem;
  top: calc(var(--toolbar-height) + 7px);
  width: min(32rem, calc(100vw - 2rem));
  max-height: min(28rem, calc(100vh - 24px));
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding: 0 0.75rem 0.75rem;
  border: 1px solid rgba(63, 111, 159, 0.18);
  border-radius: 7px;
  background: rgba(248, 251, 255, 0.98);
  box-shadow: 0 12px 32px rgba(20, 38, 63, 0.16);
  color: var(--ink);
  z-index: 40;
}

.find-panel[hidden] {
  display: none;
}

.find-panel__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
  min-height: 2.35rem;
  margin-inline: -0.75rem;
  padding: 0.3rem 0.4rem 0.3rem 0.75rem;
  border-bottom: 1px solid rgba(63, 111, 159, 0.12);
  border-radius: 7px 7px 0 0;
  background: rgba(237, 244, 252, 0.96);
  cursor: move;
  user-select: none;
  touch-action: none;
}

.find-panel.is-dragging .find-panel__header {
  cursor: grabbing;
}

.find-panel__title {
  color: #526780;
  font-size: 0.82rem;
  font-weight: 700;
  letter-spacing: 0.02em;
}

.find-panel__form {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto auto;
  align-items: center;
  gap: 0.45rem;
}

.find-panel__input {
  min-width: 0;
  height: 2rem;
  padding: 0.3rem 0.55rem;
  border: 1px solid rgba(63, 111, 159, 0.24);
  border-radius: 5px;
  background: #fff;
  color: var(--ink);
  font: inherit;
  font-size: 0.86rem;
}

.find-panel__input:focus {
  outline: 2px solid rgba(63, 111, 159, 0.18);
  border-color: rgba(63, 111, 159, 0.45);
}

.find-panel__btn {
  min-width: 2rem;
  height: 2rem;
  border: 1px solid rgba(63, 111, 159, 0.2);
  border-radius: 5px;
  background: rgba(244, 248, 253, 0.96);
  color: #4d627b;
  font-size: 0.86rem;
  font-weight: 700;
  cursor: pointer;
}

.find-panel__btn:hover:not(:disabled) {
  color: var(--accent);
  border-color: rgba(63, 111, 159, 0.34);
}

.find-panel__btn:disabled {
  opacity: 0.45;
  cursor: default;
}

.find-panel__btn--close {
  font-size: 1rem;
}

.find-panel__status {
  color: #5d6f84;
  font-size: 0.8rem;
  line-height: 1.35;
}

.find-panel__results {
  overflow: auto;
  max-height: 18rem;
  border-top: 1px solid rgba(63, 111, 159, 0.12);
  padding-top: 0.45rem;
}

.find-result {
  width: 100%;
  display: grid;
  grid-template-columns: 4.4rem minmax(0, 1fr);
  gap: 0.55rem;
  padding: 0.42rem 0.35rem;
  border: 0;
  border-radius: 5px;
  background: transparent;
  color: inherit;
  text-align: left;
  cursor: pointer;
}

.find-result:hover,
.find-result.is-active {
  background: rgba(63, 111, 159, 0.09);
}

.find-result__page {
  color: #46627f;
  font-size: 0.8rem;
  font-weight: 700;
  white-space: nowrap;
}

.find-result__snippet {
  color: #33485f;
  font-size: 0.84rem;
  line-height: 1.38;
}

.find-result__snippet mark,
.find-highlight {
  background: rgba(255, 216, 92, 0.58);
  color: inherit;
  border-radius: 0.12em;
  padding: 0 0.06em;
}

.find-highlight {
  box-shadow: 0 0 0 1px rgba(214, 154, 35, 0.26);
}

.nav-btn {
  border: 1px solid rgba(63, 111, 159, 0.22);
  background: rgba(244, 248, 253, 0.96);
  color: var(--accent);
  border-radius: 5px;
  padding: 0.36rem 0.75rem;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease, opacity 0.15s ease;
  box-shadow: 0 3px 10px rgba(20, 38, 63, 0.06);
}

.nav-btn:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 7px 18px rgba(20, 38, 63, 0.1);
}

.nav-btn:disabled {
  opacity: 0.45;
  cursor: default;
}

/* ==========================================================================
   4. Main application layout: TOC sidebar + reader stage
   ========================================================================== */
.stage {
  --toc-width-open: 312px;
  --toc-width: var(--toc-width-open);
  --toc-header-font-size: 0.92rem;
  --toc-link-font-size: 0.92rem;
  --toc-sub-link-font-size: 0.88rem;
  --toc-header-pad-top: 14px;
  --toc-header-pad-inline: 18px;
  --toc-header-pad-bottom: 8px;
  --toc-nav-pad-top: 4px;
  --toc-nav-pad-end: 12px;
  --toc-nav-pad-bottom: 16px;
  --toc-nav-pad-start: 16px;
  --toc-link-pad-y: 0.34rem;
  --toc-link-pad-x: 0.52rem;
  --toc-nested-pad-start: 0.65rem;
  --toc-chapter-gap: 0.7rem;
  --stage-inline-pad: 0px;
  height: calc(100vh - var(--toolbar-height));
  display: grid;
  grid-template-columns: var(--toc-width) minmax(0, 1fr);
  padding-inline: var(--stage-inline-pad);
  overflow: hidden;
}

body.toc-hidden .stage {
  --toc-width: 0px;
}

.toc-sidebar {
  min-width: 0;
  width: var(--toc-width);
  height: 100%;
  background: rgba(233, 240, 247, 0.9);
  border-right: 1px solid rgba(63, 111, 159, 0.12);
  overflow: hidden;
  transition: width 0.18s ease, border-color 0.18s ease, opacity 0.18s ease;
}

body.toc-hidden .toc-sidebar {
  opacity: 0;
  border-right-color: transparent;
}

.toc {
  display: flex;
  flex-direction: column;
  height: 100%;
}

.toc__header {
  padding: var(--toc-header-pad-top) var(--toc-header-pad-inline) var(--toc-header-pad-bottom);
  font-size: var(--toc-header-font-size);
  font-weight: 700;
  color: var(--text);
}

.toc__nav {
  flex: 1 1 auto;
  overflow: auto;
  padding: var(--toc-nav-pad-top) var(--toc-nav-pad-end) var(--toc-nav-pad-bottom) var(--toc-nav-pad-start);
  scrollbar-width: thin;
  scrollbar-color: rgba(63, 111, 159, 0.34) transparent;
}

.toc__list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.toc__list--nested {
  margin-top: 0.2rem;
  padding-left: var(--toc-nested-pad-start);
}

.toc__item + .toc__item {
  margin-top: 0.18rem;
}

.toc__item--chapter {
  margin-top: var(--toc-chapter-gap);
}

.toc__item--chapter:first-child {
  margin-top: 0;
}

.toc__link {
  width: 100%;
  display: block;
  border: 0;
  border-radius: 8px;
  background: transparent;
  color: var(--text);
  text-align: left;
  padding: var(--toc-link-pad-y) var(--toc-link-pad-x);
  font-size: var(--toc-link-font-size);
  cursor: pointer;
}

.toc__link:hover,
.toc__link:focus-visible {
  background: rgba(63, 111, 159, 0.10);
  outline: none;
}

.toc__label {
  min-width: 0;
  line-height: 1.38;
}

.toc__item--frontmatter > .toc__link,
.toc__item--chapter > .toc__link,
.toc__item--backmatter > .toc__link {
  font-weight: 600;
}

.toc__item--section > .toc__link,
.toc__item--references > .toc__link {
  font-size: var(--toc-sub-link-font-size);
}

/* Active TOC state: ancestor = lighter, current = stronger. */
.toc__item.is-active-ancestor > .toc__link {
  background: rgba(63, 111, 159, 0.16);
  color: #174d87;
}

.toc__item.is-active > .toc__link {
  background: rgba(63, 111, 159, 0.24);
  color: #174d87;
  font-weight: 700;
}

.reader-stage {
  min-width: 0;
  padding: 30px 14px 14px 30px;
  overflow: hidden;
}

.book-viewport {
  width: 100%;
  height: 100%;
  display: grid;
  justify-items: start;
  align-items: start;
  overflow: hidden;
  position: relative;
  padding-inline: var(--page-nav-gutter-left) var(--page-nav-gutter-right);
}

.page-nav-btn {
  width: var(--page-nav-button-width);
  height: 56px;
  display: grid;
  place-items: center;
  padding: 0;
  border: 1px solid rgba(63, 111, 159, 0.18);
  background: rgba(248, 251, 255, 0.88);
  color: rgba(63, 111, 159, 0.78);
  border-radius: 6px;
  cursor: pointer;
  position: absolute;
  top: var(--page-nav-top, 50%);
  transform: translateY(-50%);
  z-index: 9;
  box-shadow: 0 4px 12px rgba(20, 38, 63, 0.08);
  transition: transform 0.12s ease, box-shadow 0.15s ease, border-color 0.15s ease, background-color 0.15s ease, color 0.15s ease, opacity 0.15s ease;
}

.page-nav-btn svg {
  width: 14px;
  height: 28px;
  fill: currentColor;
  stroke: none;
}

.page-nav-btn--prev {
  left: var(--page-nav-prev-left, 3px);
}

.page-nav-btn--next {
  left: var(--page-nav-next-left, calc(100% - var(--page-nav-button-width) - 3px));
}

.page-nav-btn:hover:not(:disabled) {
  transform: translateY(-50%) scale(1.04);
  border-color: rgba(63, 111, 159, 0.30);
  background: rgba(248, 251, 255, 0.96);
  color: var(--accent);
  box-shadow: 0 6px 16px rgba(20, 38, 63, 0.12);
}

.page-nav-btn:disabled {
  opacity: 0.28;
  cursor: default;
  box-shadow: 0 2px 6px rgba(20, 38, 63, 0.04);
}

.book-viewport--zoomed {
  display: flex;
  justify-content: flex-start;
  align-items: flex-start;
  overflow-y: auto;
  overflow-x: auto;
  overscroll-behavior-y: contain;
  overscroll-behavior-x: contain;
  scrollbar-gutter: stable both-edges;
  cursor: grab;
}

.book-viewport--zoomed.is-pan-active {
  cursor: grabbing;
  user-select: none;
}

body.reader-pan-active,
body.reader-pan-active * {
  cursor: grabbing !important;
}

.book-scale {
  display: block;
  position: relative;
  contain: layout paint;
}

.book-viewport--zoomed .book-scale {
  margin: 0;
  flex: 0 0 auto;
  overflow: visible;
}

.book-frame {
  position: relative;
  transform-origin: top left;
}

/* ==========================================================================
   5. Spread and page geometry
   ========================================================================== */
.spread {
  width: calc(var(--page-width) * 2 + var(--page-gap));
  height: var(--page-height);
  display: grid;
  grid-template-columns: var(--page-width) var(--page-width);
  gap: var(--page-gap);
  align-items: stretch;
  justify-content: start;
}

.spread--single {
  width: var(--page-width);
  grid-template-columns: var(--page-width);
}

.spread--single .page--right {
  display: none;
}

.page {
  width: var(--page-width);
}

.page__paper {
  width: var(--page-width);
  height: var(--page-height);
  background: linear-gradient(180deg, rgba(251, 252, 254, 1) 0%, rgba(247, 249, 252, 1) 100%);
  border: 1px solid rgba(70, 90, 118, 0.08);
  box-shadow: var(--shadow);
  border-radius: 6px;
  overflow: hidden;
  display: grid;
  grid-template-rows: 1fr auto auto;
}

/* Slight inner-edge shading to suggest a physical spread. */
.page--left .page__paper {
  box-shadow: inset -10px 0 16px rgba(79, 104, 138, 0.035), var(--shadow);
}

.page--right .page__paper {
  box-shadow: inset 10px 0 16px rgba(79, 104, 138, 0.035), var(--shadow);
}

.page__inner {
  width: 100%;
  min-height: 0;
  padding: var(--page-padding-y) var(--page-padding-x) 0;
  overflow: hidden;
  position: relative;
  isolation: isolate;
  font-size: 1rem;
  line-height: var(--base-line-height);
}

.page__inner > :not(.highlight-def-layer, .reader-inline-highlight-layer) {
  position: relative;
  z-index: 1;
}

.page__inner > :first-child {
  margin-top: 0;
}

.page__footnotes {
  padding: 0 var(--page-padding-x);
}

.page__footnotes:empty {
  display: none;
}

.page-footnotes {
  margin: 0;
  padding: 0.5rem 0 0;
  border-top: 1px solid rgba(70, 90, 118, 0.18);
  color: #3b4b60;
  font-size: 0.84rem;
  line-height: 1.35;
  list-style: none;
}

.page-footnotes__item {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.35rem;
  align-items: start;
  margin: 0.18rem 0 0;
}

.page-footnotes__label {
  font-weight: 700;
  min-width: 1.2rem;
  text-align: left;
}

.page-footnotes__text {
  min-width: 0;
}

.page-footnotes__text i {
  font-style: italic;
}

.page-footnotes__text sup,
.page-footnotes__text sub {
  font-size: 0.72em;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
}

.page-footnotes__text sup {
  top: -0.32em;
}

.page-footnotes__text sub {
  top: 0.12em;
}

.page__inner .footnote-ref {
  font-size: 0.72em;
  line-height: 0;
  position: relative;
  top: -0.36em;
  vertical-align: baseline;
  letter-spacing: 0.01em;
  font-weight: 700;
}

/* Author-written chemical/text superscripts and subscripts.
   Generated citation and footnote markers use their own classes above/below. */
.page__inner sup,
.page__inner sub {
  font-size: 0.68em;
  line-height: 0;
  position: relative;
  vertical-align: baseline;
}

.page__inner sup {
  top: -0.34em;
}

.page__inner sub {
  top: 0.14em;
}

.page__footer {
  min-height: 52px;
  padding: 0.85rem var(--page-padding-x) 1rem;
  color: var(--muted);
  font-size: 0.95rem;
  text-align: center;
}

.page__number {
  display: inline-block;
  min-width: 2ch;
}

.page--unnumbered .page__number {
  opacity: 0;
}

/* Empty page slot used when a single page is shown in a two-slot structure. */
.page--empty .page__paper {
  background: transparent;
  border-color: transparent;
  box-shadow: none;
}

.page--empty .page__footer,
.page--empty .page__inner,
.page--empty .page__footnotes {
  visibility: hidden;
}

/* ==========================================================================
   6. In-page typography and generic content blocks
   ========================================================================== */
.page__inner h1,
.page__inner h2,
.page__inner h3,
.page__inner h4 {
  line-height: 1.25;
  color: #253447;
  font-weight: 600;
}

.page__inner h1 {
  margin: 0 0 1.15rem;
  font-size: var(--h1-size);
}

.page__inner h2 {
  margin: 1.3rem 0 0.82rem;
  font-size: var(--h2-size);
}

.page__inner h3 {
  margin: 1.1rem 0 0.68rem;
  font-size: var(--h3-size);
}

.page__inner h4 {
  margin: 1rem 0 0.6rem;
  font-size: var(--h4-size);
}

.page__inner p,
.page__inner li {
  font-size: var(--p-size);
  line-height: var(--base-line-height);
}

.page__inner p {
  margin: 0 0 1rem;
  text-align: justify;
}

.page__inner p[data-paragraph-split-head="true"] {
  text-align-last: justify;
}

.page__inner .glossary-entry {
  margin-bottom: 0.72rem;
}

.page__inner .glossary-entry strong {
  color: #253447;
  font-weight: 600;	
}

.page__inner .glossary-utility {
  margin: 1.2rem 0 0;
  font-size: 0.78rem;
  text-align: right;
}

.page__inner .glossary-utility a {
  color: #6b7d91;
  text-decoration: none;
  border-bottom: 1px solid rgba(107, 125, 145, 0.35);
}

.page__inner .glossary-utility a:hover,
.page__inner .glossary-utility a:focus-visible {
  color: #3f6f9f;
  border-bottom-color: currentColor;
}

/*
  Manual paragraph/figure split helper classes.

  Use case:
  - author manually ends a long paragraph earlier,
  - inserts a normal figure,
  - continues with a second paragraph fragment.

  Example:
    <p class="p-split-end">...</p>
    <figure data-fig data-caption="...">...</figure>
    <p class="p-continuation">...</p>

  p-split-end keeps the last visible line justified so the first fragment still
  reads like part of one running paragraph. p-continuation is kept neutral and
  simply suppresses any extra first-line treatment should such styling be added
  later.
*/
.page__inner p.p-split-end,
.page__inner p[data-paragraph-split-end="true"] {
  text-align-last: justify;
}

.page__inner p.p-continuation,
.page__inner p[data-paragraph-continuation="true"] {
  text-indent: 0;
}

/*
  Definition highlights are rendered by JS as flat per-line bands based on the actual client rects of the wrapped span. Adjacent highlighted lines meet at midpoint boundaries, which keeps sub/sup coverage intact without leaking into neighbouring non-highlighted lines. Authoring stays simple: <span class="highlight_def">...</span>
*/
.page__inner .highlight_def {
  color: inherit;
}

.page__inner .highlight-def-layer {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  overflow: hidden;
}

.page__inner .highlight-def-band {
  position: absolute;
  display: block;
  background: rgba(31, 49, 70, 0.08);
  border-radius: 0;
}

.page__inner ol,
.page__inner ul,
.page__inner blockquote,
.page__inner [data-block] {
  margin: 0 0 1rem;
}

.page__inner ol,
.page__inner ul {
  padding-left: 1.35rem;
}

.page__inner li {
  line-height: 1.35;
}

.page__inner li + li {
  margin-top: 0.1rem;
}

.page__inner code {
  font-size: 0.92em;
  background: rgba(63, 111, 159, 0.10);
  padding: 0.06em 0.3em;
  border-radius: 4px;
}

.page__inner figure {
  margin: 1rem auto 1.1rem;
  width: 100%;
}

.page__inner img {
  display: block;
  max-width: 98%;
  max-height: var(--content-max-image-height);
  width: auto;
  height: auto;
  margin: 0 auto;
  object-fit: contain;
  box-sizing: border-box;
  padding: 0.24rem;
  border: 1px solid rgba(63, 111, 159, 0.20);
  background: rgba(251, 253, 255, 0.98);
  border-radius: 4px;
  box-shadow: none;
}

.page__inner img[data-intrinsic-sized="true"] {
  max-width: min(var(--chem-display-width, 98%), 98%);
}

.page__inner img[data-expandable="true"] {
  cursor: zoom-in;
}

.page__inner .figure--animation {
  margin-top: 1.05rem;
}

.page__inner .molecule-animation-pair {
  display: flex;
  gap: 0.8rem;
  align-items: flex-start;
  justify-content: center;
  width: 95%;
  margin: 0 auto;
}

.page__inner .molecule-animation-panel {
  flex: 1 1 0;
  min-width: 0;
}

.page__inner .figure--animation-pair .molecule-animation-frame--small {
  width: 100%;
}

.page__inner .molecule-animation-panel-label {
  margin-top: 0.35rem;
  font-size: 0.88em;
  line-height: 1.25;
  color: #1f307e;
  text-align: center;
}

.page__inner .molecule-animation-frame,
.page__inner .molecule-animation-frame--small,
.page__inner .molecule-animation-frame--large {
  aspect-ratio: 4 / 3;
  margin: 0 auto;
  border: 1px solid rgba(63, 111, 159, 0.18);
  background: rgba(251, 253, 255, 0.98);
  border-radius: 4px;
  overflow: hidden;
}

.page__inner .molecule-animation-frame {
  width: min(95%, 28rem);
}

.page__inner .molecule-animation-frame--small {
  width: min(95%, 24rem);
}

.page__inner .molecule-animation-frame--large {
  width: min(95%, 32rem);
}

.page__inner .molecule-animation-frame iframe,
.page__inner .molecule-animation-frame--small iframe,
.page__inner .molecule-animation-frame--large iframe {
  display: block;
  width: 100%;
  height: 100%;
  border: 0;
  background: rgba(248, 251, 253, 1);
}

.page__inner figcaption {
  max-width: 95%;
  margin: 0.7rem auto 0;
  font-size: 0.95em;
  line-height: 1.35;
  color: #1f307e; /*before #2841b3 */
  text-align: center;
}

.page__inner table {
  --table-bg: rgba(234, 239, 244, 1);
  --table-head-bg: rgba(224, 230, 237, 1);
  --table-rule: rgba(93, 114, 139, 0.18);
  --table-rule-strong: rgba(93, 114, 139, 0.34);

  width: fit-content;
  max-width: 95%;
  margin: 1rem auto 1.2rem;
  border-collapse: separate;
  border-spacing: 0;
  table-layout: auto;
  background: var(--table-bg);
  border: 1px solid rgba(93, 114, 139, 0.24);
  border-radius: 0;
  overflow: hidden;
  font-size: 0.95rem;
  line-height: 1.35;
  color: var(--text);
}

.page__inner table caption {
  caption-side: bottom;
  max-width: 95%;
  margin: 0.7rem auto 0;
  padding-top: 0.1rem;
  font-size: 0.95em;
  line-height: 1.35;
  color: #202d3d;
  text-align: center;
}

.page__inner table thead th {
  background: var(--table-head-bg);
  font-weight: 600;
  border-bottom: 2px solid var(--table-rule-strong);
}

.page__inner table th,
.page__inner table td {
  padding: 0.62rem 0.8rem;
  text-align: left;
  vertical-align: top;
  border-right: 1px solid var(--table-rule);
  border-bottom: 1px solid var(--table-rule);
}

.page__inner table th {
  white-space: nowrap;
}

.page__inner table tbody td {
  background: var(--table-bg);
}

.page__inner table th:last-child,
.page__inner table td:last-child {
  border-right: none;
}

.page__inner table tbody tr:last-child td {
  border-bottom: none;
}

.page__inner table .ta-left {
  text-align: left;
}

.page__inner table .ta-center {
  text-align: center;
}

.page__inner table .ta-right {
  text-align: right;
}

.page__inner table .va-top {
  vertical-align: top;
}

.page__inner table .va-middle {
  vertical-align: middle;
}

.page__inner table .va-bottom {
  vertical-align: bottom;
}

.page__inner table .table-svg {
  display: block;
  max-width: 100%;
  height: auto;
  margin: 0 auto;
}

.page__inner table.table--with-figure {
  width: min(95%, 40rem);
}

.page__inner table.table--with-figure th,
.page__inner table.table--with-figure td {
  white-space: nowrap;
}

.page__inner table.table--with-figure th:first-child,
.page__inner table.table--with-figure td:first-child {
  width: 12.2rem;
}

.page__inner table.table--with-figure th:nth-child(2),
.page__inner table.table--with-figure td:nth-child(2) {
  width: 11.4rem;
}

.page__inner table.table--with-figure th:nth-child(3),
.page__inner table.table--with-figure td:nth-child(3) {
  width: 5.4rem;
}

.page__inner table.table--with-figure .table-figure-head,
.page__inner table.table--with-figure .table-figure-cell {
  width: 13.2rem;
  padding: 0.3rem 0.45rem;
  text-align: center;
  vertical-align: middle;
}

.page__inner table.table--with-figure .table-figure-head {
  background: var(--table-head-bg);
}

.page__inner table.table--with-figure .table-figure-cell {
  background: var(--table-bg);
}

.page__inner table.table--with-figure .table-svg--figure {
  width: 12.2rem;
  max-width: 100%;
  height: auto;
  margin: 0 auto;
}

/* ==========================================================================
   7. Front matter cards and cover visuals
   ========================================================================== */
.book-flow[data-section-type="frontmatter"] .front-card,
.page__inner .front-card {
  border: 1px solid rgba(63, 111, 159, 0.14);
  border-radius: 8px;
  background: linear-gradient(180deg, rgba(236, 243, 250, 0.94), rgba(245, 249, 254, 0.97));
  padding: 1.5rem 1.5rem 1.6rem;
}

.page__inner .front-card h1,
.page__inner .front-card h2,
.page__inner .front-card h3{
  text-align: center;
}

.page__inner .front-card p:last-child,
.page__inner .front-card ul:last-child,
.page__inner .front-card ol:last-child {
  margin-bottom: 0;
}

.page__inner .cover-card {
  min-height: 98%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  text-align: center;
  padding: 2.9rem 2.5rem 2.5rem;
  position: relative;
  overflow: hidden;
  background: linear-gradient(180deg, rgba(247, 250, 253, 0.98) 0%, rgba(239, 245, 251, 0.96) 100%);
}

.page__inner .cover-card::before {
  content: "";
  position: absolute;
  inset: 16px;
  border: 1px solid rgba(63, 111, 159, 0.10);
  border-radius: 6px;
  pointer-events: none;
}

.page__inner .cover-kicker,
.page__inner .cover-title,
.page__inner .cover-subtitle,
.page__inner .cover-author {
  position: relative;
  z-index: 1;
  text-align: center;
}

.page__inner .cover-kicker {
  margin: 0;
  text-transform: uppercase;
  letter-spacing: 0.22em;
  font-size: 0.75rem;
  font-weight: 700;
  color: #5f7690;
}

.page__inner .cover-title {
  margin: 3.35rem auto 0;
  font-size: 2.12rem;
  font-weight: 600;
  line-height: 1.08;
  letter-spacing: -0.018em;
  color: #20364b;
  white-space: nowrap;
}

.page__inner .cover-subtitle {
  margin: 1.5rem 0 0;
  padding-top: 1.2rem;
  font-size: 1.54rem;
  font-weight: 600;
  line-height: 1.2;
  letter-spacing: 0.01em;
  color: #45617c;
}

.page__inner .cover-subtitle::before,
.page__inner .cover-author::before {
  content: "";
  display: block;
  width: 7rem;
  height: 0;
  margin: 0 auto;
  border-top: 1px solid rgba(70, 106, 146, 0.24);
}

.page__inner .cover-subtitle::after,
.page__inner .cover-author::after {
  content: none;
}

.page__inner .cover-subtitle::before {
  margin-bottom: 1rem;
}

.page__inner .cover-author {
  margin: 1.9rem auto 0;
  padding-top: 1rem;
  font-size: 1.03rem;
  font-weight: 600;
  line-height: 1.2;
  letter-spacing: 0.12em;
  color: #5a7087;
}

.page__inner .cover-author::before {
  width: 5.2rem;
  margin-bottom: 0.95rem;
}

.page__inner .cover-image-wrap {
  width: 100%;
  margin-top: 9rem;
  display: flex;
  justify-content: center;
}

.page__inner .cover-image {
  display: block;
  width: min(82%, 30rem);
  max-width: 100%;
  height: auto;
  max-height: 15.5rem;
  margin: 0 auto;
  padding: 0;
  border: 0;
  border-radius: 0;
  background: transparent;
  box-shadow: none;
  object-fit: contain;
}

.page__inner .front-grid {

  display: grid;
  gap: 0.8rem;
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

/* Unified About + Preface frontmatter blocks.
   The same class is applied to the top-level pagination blocks because the
   article wrapper itself is not copied into rendered pages. */
.page__inner h2.intro,
.page__inner h3.intro,
.page__inner h4.intro,
.page__inner p.intro {
  background: rgba(63, 111, 159, 0.065);
}

.page__inner h2.intro,
.page__inner h3.intro {
  text-align: center;
}

.page__inner h2.intro,
.page__inner h3.intro,
.page__inner h4.intro {
  margin-bottom: 0;
  padding: 0.55rem 0.85rem 0.28rem;
  border-radius: 6px 6px 0 0;
}

.page__inner p.intro {
  margin: 0 0 0.78rem;
  padding: 0.42rem 0.85rem 0.55rem;
  border-radius: 6px;
}

.page__inner h2.intro + p.intro,
.page__inner h3.intro + p.intro,
.page__inner h4.intro + p.intro {
  border-radius: 0 0 6px 6px;
}

.page__inner p.intro + p.intro {
  margin-top: -0.78rem;
  padding-top: 0.22rem;
  border-radius: 0 0 6px 6px;
}

.page__inner h3.intro + h4.intro,
.page__inner h4.intro + h4.intro {
  margin-top: 0;
  border-radius: 0;
}

.page__inner hr.intro {
  margin: 0.9rem 0;
}

.page__inner .contents-card {
  padding-top: 1.6rem;
}

.page__inner .generated-contents {
  margin-top: 1.25rem;
}

.page__inner .contents-nav {
  font-size: 0.94rem;
  line-height: 1.32;
}

.page__inner .contents-list {
  margin: 0;
  padding-left: 0;
}

.page__inner .contents-list--chapters,
.page__inner .contents-list--chapter-children {
  list-style: none;
}

.page__inner .contents-list--chapter-children {
  margin-top: 0.25rem;
  padding-left: 1.05rem;
}

.page__inner .contents-list--h2-children,
.page__inner .contents-list--h3-children {
  margin-top: 0.16rem;
  padding-left: 1.35rem;
  list-style: disc;
}

.page__inner .contents-entry {
  break-inside: avoid;
}

.page__inner li[data-list-item-continuation="true"]::marker {
  content: "";
}

.page__inner .contents-entry--chapter,
.page__inner .contents-entry--backmatter {
  margin-top: 0.95rem;
  font-weight: 650;
}

.page__inner .contents-entry--chapter:first-child {
  margin-top: 0;
}

.page__inner .contents-entry--h2 {
  margin-top: 0.42rem;
  font-weight: 560;
}

.page__inner .contents-entry--h3 {
  margin-top: 0.18rem;
  font-weight: 430;
}

.page__inner .contents-entry--h4 {
  margin-top: 0.1rem;
  font-size: 0.86em;
  color: #5b6b7d;
  font-weight: 400;
}

.page__inner .contents-entry .contents-link {
  color: #294f78;
  text-decoration: none;
  border-bottom: none;
}

.page__inner .contents-entry--chapter > .contents-link,
.page__inner .contents-entry--backmatter > .contents-link,
.page__inner .contents-entry--h2 > .contents-link {
  text-decoration: underline;
  text-underline-offset: 0.12em;
  text-decoration-thickness: 1px;
}

.page__inner .contents-entry .contents-link:hover,
.page__inner .contents-entry .contents-link:focus-visible {
  color: #173d64;
}


/* ==========================================================================
   8. Citations, generated references, and citation tooltip
   ========================================================================== */
.page__inner cite {
  font-style: normal;
}

.page__inner .cite-ref {
  font-size: 0.78em;
  line-height: 0;
  position: relative;
  top: -0.36em;
  vertical-align: baseline;
  color: var(--accent);
  font-weight: 600;
  margin-left: 0.1em;
}

.page__inner .cite-link {
  color: inherit;
  text-decoration: none;
  border-radius: 0.3rem;
  padding: 0 0.04rem;
  cursor: pointer;
}

.page__inner .cite-link:hover,
.page__inner .cite-link:focus-visible {
  text-decoration: underline;
  outline: none;
  background: rgba(63, 111, 159, 0.10);
}
.page__inner .cite-link--range {
  white-space: nowrap;
}


.page__inner .reader-nav-link {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 0.12em;
  text-decoration-thickness: 1px;
  font-weight: inherit;
  border-radius: 0.2rem;
}

.page__inner .reader-nav-link:hover,
.page__inner .reader-nav-link:focus-visible {
  outline: none;
  background: rgba(63, 111, 159, 0.10);
}


.page__inner .fig-preview-button {
  appearance: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.25em;
  height: 1.25em;
  margin-left: 0.22em;
  border: 1px solid rgba(63, 111, 159, 0.24);
  border-radius: 0.28em;
  background: rgba(63, 111, 159, 0.06);
  color: var(--accent);
  font: inherit;
  font-size: 0.82em;
  line-height: 1;
  vertical-align: 0.06em;
  cursor: pointer;
}

.page__inner .fig-preview-button:hover,
.page__inner .fig-preview-button:focus-visible {
  outline: none;
  background: rgba(63, 111, 159, 0.14);
  border-color: rgba(63, 111, 159, 0.42);
}

.page__inner .reader-nav-target-marker {
  display: inline-block;
  width: 0;
  height: 0;
  overflow: hidden;
  pointer-events: none;
  vertical-align: baseline;
}

.page__inner .reader-inline-target {
  border-radius: 0.2rem;
}

.page__inner .reader-nav-highlight {
  background: rgba(74, 134, 204, 0.14);
  box-shadow: 0 0 0 2px rgba(74, 134, 204, 0.24);
  border-radius: 0.3rem;
  transition: background-color 0.18s ease, box-shadow 0.18s ease;
}

.page__inner .reader-inline-highlight-layer {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  overflow: hidden;
}

.page__inner .reader-inline-highlight-band {
  position: absolute;
  display: block;
  background: rgba(74, 134, 204, 0.14);
  border-radius: 0;
}

.page__inner .references-subtitle {
  margin: 0 0 1.15rem;
  font-size: 1.3rem;
  line-height: 1.3;
  font-weight: 700;
  color: var(--text);
}

.page__inner .reference-list {
  font-size: 0.90rem;
  line-height: 1.2;	
}

.page__inner .reference-list li {
  margin-bottom: 0.50rem;
  text-align: left;
}

.page__inner .reference-entry {
  border-radius: 10px;
  transition: background-color 0.25s ease, box-shadow 0.25s ease;
}

.page__inner .reference-entry--active {
  background: rgba(74, 134, 204, 0.20);
  box-shadow: 0 0 0 2px rgba(74, 134, 204, 0.38);
}

.page__inner .ref-link {
  display: inline-flex;
  align-items: center;
  margin-left: 0.3rem;
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 0.12em;
}

.citation-tooltip {
  position: fixed;
  z-index: 60;
  max-width: min(34rem, calc(100vw - 28px));
  padding: 0.6rem 0.72rem;
  border-radius: 10px;
  background: rgba(24, 39, 61, 0.97);
  color: #f8fbff;
  font-size: 0.88rem;
  line-height: 1.35;
  box-shadow: 0 16px 30px rgba(9, 18, 34, 0.26);
  pointer-events: none;
}

.citation-tooltip--interactive {
  pointer-events: auto;
}

.citation-tooltip__label {
  margin-bottom: 0.4rem;
  font-size: 0.76rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  opacity: 0.78;
}

.citation-tooltip__group-list {
  display: grid;
  gap: 0.22rem;
}

.citation-tooltip__ref-link {
  appearance: none;
  width: 100%;
  border: 0;
  border-radius: 0.38rem;
  padding: 0.16rem 0.22rem;
  background: transparent;
  color: inherit;
  font: inherit;
  text-align: left;
  cursor: pointer;
}

.citation-tooltip__ref-link:hover,
.citation-tooltip__ref-link:focus-visible,
.citation-tooltip__ref-link.is-active {
  outline: none;
  background: rgba(255, 255, 255, 0.16);
}

.citation-tooltip__ref-number {
  display: inline-block;
  min-width: 2.1rem;
  font-weight: 700;
}

.citation-tooltip__ref-preview {
  overflow-wrap: anywhere;
}

/* ==========================================================================
   9. Floating static figure preview
   ========================================================================== */
.figure-preview[hidden] {
  display: none;
}

.figure-preview {
  position: fixed;
  left: 1rem;
  top: 1rem;
  z-index: 65;
  width: min(52vw, 780px);
  max-width: calc(100vw - 28px);
  max-height: calc(100vh - 28px);
  overflow: hidden;
  border: 1px solid rgba(63, 111, 159, 0.22);
  border-radius: 10px;
  background: rgba(247, 250, 254, 0.99);
  box-shadow: 0 18px 42px rgba(12, 23, 40, 0.20);
}

.figure-preview__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.6rem;
  min-height: 2.45rem;
  padding: 0.34rem 0.45rem 0.34rem 0.72rem;
  border-bottom: 1px solid rgba(63, 111, 159, 0.14);
  background: rgba(237, 244, 252, 0.96);
  cursor: move;
  user-select: none;
}

.figure-preview.is-dragging .figure-preview__header {
  cursor: grabbing;
}

.figure-preview__title {
  min-width: 0;
  color: #253447;
  font-size: 0.92rem;
  font-weight: 600;
  line-height: 1.2;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.figure-preview__close {
  min-width: 2rem;
  padding-inline: 0.55rem;
  flex: 0 0 auto;
}

.figure-preview__body {
  display: grid;
  gap: 0.48rem;
  padding: 0.72rem;
  max-height: calc(100vh - 5.4rem);
  overflow: auto;
}

.figure-preview__image {
  display: block;
  max-width: 100%;
  max-height: min(56vh, 620px);
  width: auto;
  height: auto;
  margin: 0 auto;
  padding: 0.18rem;
  border: 1px solid rgba(63, 111, 159, 0.18);
  border-radius: 4px;
  background: rgba(251, 253, 255, 0.98);
  box-shadow: none;
  object-fit: contain;
}

.figure-preview__caption {
  color: var(--muted);
  font-size: 0.86rem;
  line-height: 1.32;
  text-align: left;
}

@media (max-width: 780px) {
  .figure-preview {
    width: calc(100vw - 28px);
  }
}

/* ==========================================================================
   10. Expanded figure overlay viewer
   ========================================================================== */
.figure-overlay[hidden] {
  display: none;
}

.figure-overlay {
  position: fixed;
  inset: 0;
  z-index: 70;
  display: grid;
  place-items: center;
  padding: clamp(18px, 3vw, 32px);
}

.figure-overlay__backdrop {
  position: absolute;
  inset: 0;
  background: rgba(18, 31, 47, 0.34);
}

.figure-overlay__dialog {
  position: relative;
  width: min(92vw, 1500px);
  max-height: 88vh;
  padding: 0.95rem 0.95rem 0.8rem;
  border: 1px solid rgba(63, 111, 159, 0.18);
  border-radius: 10px;
  background: rgba(247, 250, 254, 0.985);
  box-shadow: 0 22px 48px rgba(12, 23, 40, 0.18);
}

.figure-overlay__content {
  display: flex;
  align-items: center;
  justify-content: center;
}

.figure-overlay__image {
  display: block;
  max-width: 100%;
  max-height: calc(88vh - 2.2rem);
  width: auto;
  height: auto;
  margin: 0 auto;
  padding: 0;
  border: 0;
  border-radius: 0;
  background: transparent;
  box-shadow: none;
  object-fit: contain;
}

.figure-overlay__close {
  position: absolute;
  top: 0.55rem;
  right: 0.55rem;
  min-width: 2.25rem;
  padding-inline: 0.65rem;
  z-index: 1;
}

body.figure-overlay-open {
  overflow: hidden;
}

/* ==========================================================================
   11. Hidden measurement layer used by the paginator
   ========================================================================== */
#measureLayer {
  position: absolute;
  left: -99999px;
  top: 0;
  width: var(--page-width);
  visibility: hidden;
  pointer-events: none;
}

.page--measure {
  width: var(--page-width);
}

.page--measure .page__paper {
  width: var(--page-width);
  height: var(--page-height);
}

/* ==========================================================================
   11. Responsive shell adjustments
   ========================================================================== */
@media (max-width: 1180px) {
  .stage {
    --toc-width-open: 248px;
  }

  .toolbar {
    gap: 10px;
    padding-inline: 12px;
  }

  .reader-stage {
    padding: 24px 10px 10px 30px;
  }
}

@media (max-width: 960px) {
  :root {
    --page-nav-gutter-left: 30px;
    --page-nav-gutter-right: 30px;
    --page-nav-button-width: 24px;
    --page-nav-gap: 4px;
  }

  .toolbar {
    grid-template-columns: auto minmax(0, 1fr);
    row-gap: 6px;
  }

  .toolbar__spacer {
    display: none;
  }

  .toolbar__group--right {
    justify-self: end;
  }

  .stage {
    --toc-width: 0px;
  }

  .toc-sidebar {
    opacity: 0;
    border-right-color: transparent;
  }
}
/* Static document title for semantic structure; kept outside the paginated reader. */
.ebook-site-title {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}