:root {
  --paper: #fbfaf5;
  --ink: #242522;
  --muted: #6c7069;
  --accent: #2f6f61;
  --accent-soft: #e1eee9;
  --line: #d8ddd7;
  --sidebar: #f1f4ef;
  --code: #1d2522;
  --code-ink: #e7f1ec;
  --sidebar-width: 19rem;
  --font-scale: 1;
}
:root[data-theme="dark"] {
  --paper: #0d1411;
  --ink: #cfe8d6;
  --muted: #a8d4b4;
  --accent: #9cf5b8;
  --accent-soft: #193426;
  --line: #2e443a;
  --sidebar: #111a15;
  --code: #101815;
  --code-ink: #e7f1ec;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--paper);
  color: var(--ink);
  font-family: Georgia, "Times New Roman", "Noto Serif CJK SC", "Songti SC", SimSun, serif;
  line-height: 1.75;
}
a { color: var(--accent); }
body.reading { min-height: 100vh; overflow-x: hidden; }
main.reading {
  width: min(94vw, 62rem);
  max-width: 100%;
  margin: 0 auto;
  padding: 2.75rem 1.25rem 5rem;
  font-size: calc(1rem * var(--font-scale));
  overflow-wrap: break-word;
}
main.reading h1,
main.reading h2,
main.reading h3,
main.reading h4,
main.reading h5,
main.reading h6 {
  color: var(--accent);
  line-height: 1.3;
  margin: 2rem 0 .7rem;
  scroll-margin-top: 1rem;
}
main.reading h1.chapterNumber {
  color: var(--muted);
  font: 700 4.2rem/1 "Segoe UI", Arial, sans-serif;
  margin: .25rem 0 0;
  text-align: center;
}
main.reading > h1:first-child:not(.chapterNumber) {
  color: var(--ink);
  font-size: 2rem;
  margin: .9rem 0 2rem;
  text-align: center;
}
main.reading h1.chapterTitle {
  color: var(--ink);
  font-size: 2rem;
  margin: .9rem 0 2rem;
  text-align: center;
}
main.reading h1.heading-1,
main.reading h1:not(.chapterNumber):not(.chapterTitle) { font-size: 1.65rem; }
main.reading h2 { font-size: 1.35rem; }
main.reading h3 { font-size: 1.12rem; }
main.reading h4 { font-size: 1rem; }
main.reading p { margin: .75rem 0; text-align: justify; }
main.reading p.center,
main.reading p.packt_figref,
main.reading p.cite { text-align: center; }
main.reading p.packt_figref { color: var(--muted); font-size: .9rem; font-style: italic; }
main.reading ul,
main.reading ol { margin: .75rem 0; padding-left: 2rem; }
main.reading li { margin: .25rem 0; }
main.reading blockquote {
  border-left: 3px solid var(--accent);
  color: var(--muted);
  margin: 1.25rem 0;
  padding: .25rem 1rem;
}
main.reading figure { margin: 1.5rem auto; text-align: center; }
main.reading figure > img,
main.reading p.center > img,
main.reading img { height: auto; max-width: 100%; }
main.reading figure > img { max-width: 90%; }
main.reading table {
  border-collapse: collapse;
  display: block;
  margin: 1.25rem auto;
  max-width: 100%;
  overflow-x: auto;
  width: fit-content;
}
main.reading th,
main.reading td { border: 1px solid var(--line); padding: .35rem .7rem; }
main.reading table.equation-table { width: 100%; }
main.reading table.equation-table th {
  font-style: italic;
  font-weight: 400;
  text-align: left;
  white-space: nowrap;
}
main.reading table.equation-table td { text-align: left; }
main.reading table.equation-table mjx-container { margin: 0 !important; }
main.reading pre {
  background: var(--code);
  border-radius: .35rem;
  color: var(--code-ink);
  line-height: 1.4;
  margin: 1.1rem 0;
  overflow-x: auto;
  padding: 1rem;
  white-space: pre;
}
main.reading code,
main.reading pre { font-family: Consolas, "Courier New", monospace; }
main.reading pre code { display: block; line-height: inherit; }
main.reading :not(pre) > code { background: #edf1ed; border-radius: .2rem; padding: .08rem .3rem; }
main.reading mjx-container { max-width: 100%; overflow-x: auto; overflow-y: hidden; }
main.reading .note,
main.reading .packt_tip {
  background: var(--accent-soft);
  border-left: 4px solid var(--accent);
  margin: 1.2rem 0;
  padding: .65rem 1rem;
}
main.reading .note p,
main.reading .packt_tip p { margin: .35rem 0; }

/* Framework pages: the chapter reader is kept in the right pane. */
body.frame { overflow: hidden; }
.frame-bar {
  align-items: center;
  background: var(--paper);
  border-bottom: 1px solid var(--line);
  display: flex;
  gap: .75rem;
  height: 3.6rem;
  padding: 0 .9rem;
  position: relative;
  z-index: 3;
}
.frame-bar h1 {
  color: var(--ink);
  flex: 1;
  font-size: 1rem;
  margin: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.icon-button {
  align-items: center;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: .35rem;
  color: var(--ink);
  cursor: pointer;
  display: inline-flex;
  font-size: 1.15rem;
  height: 2.25rem;
  justify-content: center;
  width: 2.35rem;
}
.icon-button:hover,
.toc-link:hover { background: var(--accent-soft); }
.reading-tools { display: flex; gap: .35rem; position: fixed; right: .75rem; top: .7rem; z-index: 10; }
.reading-tools .icon-button { font-size: .85rem; width: 2.3rem; }
.floating-toc-button {
  left: .75rem;
  position: fixed;
  top: .75rem;
  z-index: 10;
}
.frame-layout { display: flex; height: 100vh; position: relative; }
#toc {
  background: var(--sidebar);
  border-right: 1px solid var(--line);
  flex: 0 0 var(--sidebar-width);
  overflow-y: auto;
  padding: 4.2rem .7rem 2rem;
  transition: margin-left .2s ease;
}
.toc-title { color: var(--ink); font-size: 1.05rem; font-weight: 700; line-height: 1.35; margin: .2rem .55rem .6rem; }
.toc-heading { color: var(--muted); font-size: .75rem; letter-spacing: .08em; margin: .15rem .55rem .8rem; text-transform: uppercase; }
#toc details { border-bottom: 1px solid var(--line); padding: .15rem 0 .4rem; }
#toc summary { color: var(--ink); cursor: pointer; list-style-position: inside; padding: .45rem .35rem; }
.toc-link { border-radius: .25rem; color: var(--ink); display: block; font-size: .92rem; line-height: 1.35; padding: .38rem .55rem .38rem 1.35rem; text-decoration: none; }
.toc-link.active { background: var(--accent-soft); color: var(--accent); font-weight: 700; }
#reader-pane { flex: 1; min-width: 0; }
#reader { border: 0; display: block; height: 100%; width: 100%; }
body.toc-collapsed #toc { margin-left: calc(-1 * var(--sidebar-width)); }

/* Chinese: replace italic with bold — CJK fonts lack true italic glyphs */
:lang(zh) em,
:lang(zh) i,
:lang(zh) .italic {
  font-style: normal;
  font-weight: bold;
}
:lang(zh) main.reading p.packt_figref,
:lang(zh) main.reading table.equation-table th {
  font-style: normal;
  font-weight: bold;
}

@media (max-width: 760px) {
  main.reading { padding: 1.5rem .9rem 4rem; width: 100%; }
  body.reading { overflow-x: hidden; }
  main.reading h1.chapterTitle { font-size: 1.6rem; }
  .frame-bar h1 { font-size: .92rem; }
  #toc { bottom: 0; box-shadow: 4px 0 16px rgba(0, 0, 0, .08); left: 0; position: absolute; top: 0; width: var(--sidebar-width); z-index: 2; }
  body.toc-collapsed #toc { margin-left: calc(-1 * var(--sidebar-width)); visibility: hidden; }
  body:not(.toc-collapsed) #toc { visibility: visible; }
}