:root {
  color-scheme: light;
  --bg: #f8f6f0;
  --panel: #ffffff;
  --text: #17201d;
  --muted: #53635d;
  --border: #d8ded8;
  --accent: #0f766e;
  --accent-strong: #134e4a;
  --code-bg: #17201d;
  --code-text: #ecfdf5;
  --shadow: 0 18px 40px rgb(23 32 29 / 10%);
  font-family: "Avenir Next", "Segoe UI", system-ui, sans-serif;
}

[data-theme="dark"] {
  color-scheme: dark;
  --bg: #121514;
  --panel: #1c211f;
  --text: #edf3ef;
  --muted: #a8b8b0;
  --border: #35413c;
  --accent: #5eead4;
  --accent-strong: #99f6e4;
  --code-bg: #080b0a;
  --code-text: #e7fff8;
  --shadow: 0 18px 40px rgb(0 0 0 / 24%);
}

[data-theme="sepia"] {
  color-scheme: light;
  --bg: #f4ecd9;
  --panel: #fffaf0;
  --text: #2a2118;
  --muted: #67594a;
  --border: #d9c9aa;
  --accent: #8a4b21;
  --accent-strong: #5e3218;
  --code-bg: #2d241c;
  --code-text: #fff6e5;
}

[data-theme="contrast"] {
  color-scheme: dark;
  --bg: #000000;
  --panel: #050505;
  --text: #ffffff;
  --muted: #f2f2f2;
  --border: #ffffff;
  --accent: #ffdd00;
  --accent-strong: #ffffff;
  --code-bg: #000000;
  --code-text: #ffffff;
}

[data-theme="calm"] {
  color-scheme: light;
  --bg: #eef7f3;
  --panel: #fbfffd;
  --text: #16251f;
  --muted: #52685e;
  --border: #bfd8cd;
  --accent: #2f6f93;
  --accent-strong: #1f4d66;
  --code-bg: #17242b;
  --code-text: #e9f8ff;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-size: 18px;
  line-height: 1.65;
}
a { color: var(--accent-strong); }
a:hover { color: var(--accent); }
.skip-link {
  position: absolute;
  left: 1rem;
  top: -10rem;
  z-index: 10;
  background: var(--accent);
  color: var(--panel);
  padding: .5rem .75rem;
}
.skip-link:focus { top: 1rem; }
.site-header {
  align-items: center;
  background: var(--panel);
  border-bottom: 1px solid var(--border);
  display: grid;
  gap: 1rem;
  grid-template-columns: 1fr auto;
  padding: .85rem clamp(1rem, 3vw, 2.5rem);
  position: sticky;
  top: 0;
  z-index: 5;
}
.brand {
  color: var(--text);
  font-weight: 800;
  text-decoration: none;
}
.header-actions {
  align-items: center;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: flex-end;
}
.site-header nav {
  display: flex;
  gap: 1rem;
  font-size: .95rem;
}
.site-header nav a { text-decoration: none; }
.theme-picker {
  align-items: center;
  display: flex;
  gap: .45rem;
  font-size: .9rem;
}
.theme-picker select {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: .35rem;
  color: var(--text);
  font: inherit;
  padding: .3rem .45rem;
}
.edit-toggle {
  background: var(--accent-strong);
  border: 1px solid var(--accent-strong);
  border-radius: .35rem;
  color: var(--panel);
  cursor: pointer;
  font: inherit;
  font-weight: 700;
  padding: .35rem .7rem;
}
.edit-toggle:hover {
  background: var(--accent);
  border-color: var(--accent);
}
.site-footer {
  border-top: 1px solid var(--border);
  color: var(--muted);
  margin-top: 4rem;
  padding: 1.5rem clamp(1rem, 3vw, 2.5rem);
  text-align: center;
}
.site-footer p {
  margin: 0;
}
.hero {
  display: grid;
  gap: 2rem;
  grid-template-columns: minmax(0, 1fr) 22rem;
  margin: 0 auto;
  max-width: 72rem;
  padding: clamp(2rem, 6vw, 5rem) clamp(1rem, 3vw, 2.5rem);
}
.hero-copy h1 {
  font-family: Georgia, Cambria, "Times New Roman", serif;
  font-size: clamp(2.6rem, 6vw, 5.25rem);
  letter-spacing: 0;
  line-height: 1;
  margin: .25rem 0 1rem;
  max-width: 11ch;
}
.hero-copy p:not(.eyebrow) {
  color: var(--muted);
  max-width: 42rem;
}
.eyebrow,
.chapter-kicker,
.book-sidebar > p,
.local-toc > p {
  color: var(--muted);
  font-size: .78rem;
  font-weight: 800;
  letter-spacing: .08em;
  margin: 0 0 .75rem;
  text-transform: uppercase;
}
.primary-link {
  background: var(--accent-strong);
  border-radius: .35rem;
  color: var(--panel);
  display: inline-flex;
  font-weight: 700;
  margin-top: 1rem;
  padding: .65rem .9rem;
  text-decoration: none;
}
.primary-link:hover { color: var(--panel); background: var(--accent); }
.course-panel {
  align-self: end;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: .5rem;
  box-shadow: var(--shadow);
  padding: 1rem;
}
.course-panel dl,
.course-panel dd { margin: 0; }
.course-panel div + div { border-top: 1px solid var(--border); margin-top: .8rem; padding-top: .8rem; }
.course-panel dt { color: var(--muted); font-size: .8rem; font-weight: 700; text-transform: uppercase; }
.course-panel dd { font-weight: 700; line-height: 1.35; margin-top: .2rem; }
.home-main {
  margin: 0 auto 4rem;
  max-width: 72rem;
  padding: 0 clamp(1rem, 3vw, 2.5rem);
}
.home-main h2 {
  font-family: Georgia, Cambria, "Times New Roman", serif;
  font-size: 2rem;
  line-height: 1.15;
}
.chapter-grid {
  display: grid;
  gap: .85rem;
  grid-template-columns: repeat(auto-fit, minmax(17rem, 1fr));
  list-style: none;
  margin: 1.5rem 0 0;
  padding: 0;
}
.chapter-grid a {
  background: var(--panel);
  border: 1px solid var(--border);
  border-left: .35rem solid var(--accent);
  border-radius: .35rem;
  color: var(--text);
  display: block;
  min-height: 8rem;
  padding: 1rem;
  text-decoration: none;
}
.chapter-grid .is-unpublished a {
  border-left-color: var(--border);
  color: var(--muted);
  cursor: default;
  opacity: .68;
}
.chapter-grid span {
  color: var(--muted);
  display: block;
  font-size: .85rem;
  font-weight: 700;
  margin-bottom: .5rem;
  text-transform: uppercase;
}
.chapter-grid strong {
  display: block;
  font-size: 1.2rem;
  line-height: 1.3;
}
.chapter-grid em {
  color: var(--muted);
  display: block;
  font-size: .85rem;
  font-style: normal;
  font-weight: 700;
  margin-top: .85rem;
}
.chapter-grid em:empty {
  display: none;
}
.book-shell {
  display: grid;
  gap: clamp(1rem, 3vw, 2rem);
  grid-template-columns: 18rem minmax(0, 48rem) 15rem;
  margin: 0 auto;
  max-width: 88rem;
  padding: 2rem clamp(1rem, 3vw, 2.5rem) 5rem;
}
.book-sidebar,
.local-toc {
  align-self: start;
  max-height: calc(100vh - 6rem);
  overflow: auto;
  position: sticky;
  top: 5rem;
}
.book-sidebar ol,
.local-toc ol {
  list-style: none;
  margin: 0;
  padding: 0;
}
.book-sidebar a {
  align-items: baseline;
  border-radius: .35rem;
  color: var(--text);
  display: grid;
  gap: .55rem;
  grid-template-columns: 1.6rem 1fr;
  line-height: 1.3;
  padding: .45rem .55rem;
  text-decoration: none;
}
.book-sidebar a[aria-current="page"] {
  background: var(--panel);
  box-shadow: inset 3px 0 0 var(--accent);
  font-weight: 800;
}
.book-sidebar span {
  color: var(--muted);
  font-size: .8rem;
  font-weight: 800;
}
.local-toc a {
  color: var(--muted);
  display: block;
  font-size: .88rem;
  line-height: 1.35;
  padding: .25rem 0;
  text-decoration: none;
}
.local-toc .toc-level-3 { padding-left: .8rem; }
.chapter-main {
  min-width: 0;
}
.editor-panel {
  background: var(--panel);
  border: 1px solid var(--border);
  border-left: .35rem solid var(--accent);
  border-radius: .5rem;
  box-shadow: var(--shadow);
  display: grid;
  gap: 1rem;
  margin-bottom: 1rem;
  padding: 1rem;
}
.editor-panel[hidden] {
  display: none;
}
.editor-panel h2 {
  font-family: Georgia, Cambria, "Times New Roman", serif;
  font-size: 1.35rem;
  line-height: 1.2;
  margin: 0;
}
.editor-panel p {
  color: var(--muted);
  font-size: .9rem;
  margin: .25rem 0 0;
}
.editor-panel textarea {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: .35rem;
  color: var(--text);
  font: .95rem/1.55 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  min-height: 32rem;
  padding: .8rem;
  resize: vertical;
  width: 100%;
}
.editor-panel .EasyMDEContainer {
  color: var(--text);
}
.editor-panel .EasyMDEContainer .CodeMirror {
  background: var(--bg);
  border-color: var(--border);
  color: var(--text);
  font: .95rem/1.55 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}
.editor-panel .EasyMDEContainer .CodeMirror-cursor {
  border-left-color: var(--text);
}
.editor-panel .EasyMDEContainer .CodeMirror-selected {
  background: color-mix(in srgb, var(--accent) 24%, transparent);
}
.editor-panel .editor-toolbar {
  background: var(--panel);
  border-color: var(--border);
  border-radius: .35rem .35rem 0 0;
}
.editor-panel .editor-toolbar button {
  color: var(--text) !important;
}
.editor-panel .editor-toolbar button:hover,
.editor-panel .editor-toolbar button.active {
  background: var(--bg);
  border-color: var(--border);
}
.editor-panel .editor-toolbar i.separator {
  border-left-color: var(--border);
  border-right-color: transparent;
}
.editor-panel .editor-preview,
.editor-panel .editor-preview-side {
  background: var(--panel);
  color: var(--text);
}
.editor-actions {
  align-items: center;
  display: flex;
  flex-wrap: wrap;
  gap: .75rem;
}
.editor-actions button {
  border: 1px solid var(--border);
  border-radius: .35rem;
  cursor: pointer;
  font: inherit;
  font-weight: 700;
  padding: .45rem .75rem;
}
.editor-actions button:first-child {
  background: var(--accent-strong);
  border-color: var(--accent-strong);
  color: var(--panel);
}
.editor-actions button:first-child:hover {
  background: var(--accent);
  border-color: var(--accent);
}
.editor-actions button:last-of-type {
  background: var(--panel);
  color: var(--text);
}
.editor-actions span {
  color: var(--muted);
  font-size: .9rem;
}
.prose {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: .5rem;
  box-shadow: var(--shadow);
  padding: clamp(1.25rem, 4vw, 3rem);
}
.prose h1,
.prose h2,
.prose h3,
.prose h4 {
  font-family: Georgia, Cambria, "Times New Roman", serif;
  letter-spacing: 0;
  line-height: 1.2;
}
.prose h1 {
  border-top: .35rem solid var(--accent);
  font-size: clamp(2.2rem, 5vw, 4rem);
  margin: 0 0 1.5rem;
  padding-top: 1.2rem;
}
.prose h2 { font-size: 2rem; margin-top: 2.5rem; }
.prose h3 { font-size: 1.45rem; margin-top: 2rem; }
.prose p,
.prose li { max-width: 68ch; }
.prose img { max-width: 100%; }
.prose blockquote {
  border-left: .3rem solid var(--accent);
  color: var(--muted);
  margin-left: 0;
  padding-left: 1rem;
}
.prose pre {
  background: var(--code-bg);
  border-radius: .35rem;
  color: var(--code-text);
  overflow: auto;
  padding: 1rem;
}
.prose code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: .9em;
}
.heading-anchor {
  color: var(--muted);
  font-family: system-ui, sans-serif;
  font-size: .55em;
  margin-left: .35rem;
  opacity: .65;
  text-decoration: none;
}
.chapter-pagination {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  margin-top: 1rem;
}
.chapter-pagination a {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: .35rem;
  color: var(--text);
  display: block;
  line-height: 1.35;
  padding: .8rem;
  text-decoration: none;
}
.chapter-pagination a:last-child { text-align: right; }
.chapter-pagination span {
  color: var(--muted);
  display: block;
  font-size: .78rem;
  font-weight: 800;
  text-transform: uppercase;
}
@media (max-width: 76rem) {
  .book-shell { grid-template-columns: minmax(0, 1fr); }
  .book-sidebar,
  .local-toc {
    max-height: none;
    position: static;
  }
  .book-sidebar ol { columns: 2; }
  .local-toc { display: none; }
}
@media (max-width: 48rem) {
  body { font-size: 16px; }
  .site-header { grid-template-columns: 1fr; position: static; }
  .header-actions { justify-content: flex-start; }
  .site-header nav { flex-wrap: wrap; }
  .hero { grid-template-columns: 1fr; }
  .book-sidebar ol { columns: 1; }
  .chapter-pagination { grid-template-columns: 1fr; }
  .chapter-pagination a:last-child { text-align: left; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .01ms !important;
  }
}