/* Book chrome — Zed-like wireframe / monospace / disappearing UI */

:root {
  --content-max: none;
  --sidebar: clamp(16rem, 22vw, 22rem);
  --layout-pad: clamp(0.75rem, 2vw, 1.75rem);
  --header-gap: clamp(1.25rem, 2.5vw, 2.5rem);
  --ease-out: var(--ease);
  --ease-in-out: var(--ease);
  --ease-soft: var(--ease);
  --dur-fast: 0.1s;
  --dur: 0.18s;
  --dur-slow: 0.24s;
  --display: var(--mono);
  --hub-accent: var(--accent);
  --hub-accent-dim: var(--accent-dim);
  --hub-line: var(--line);
  --hub-line-strong: var(--line-strong);
  --hub-surface: var(--surface);
  --hub-bg: var(--bg);
  --hard-shadow: none;
  --hard-shadow-lg: none;
}

html {
  color-scheme: dark;
  scroll-behavior: smooth;
}

body {
  font-family: var(--mono) !important;
  font-size: 14px !important;
  color: var(--ink) !important;
  background: var(--bg) !important;
  font-feature-settings: "liga" 1, "calt" 1;
}

body::before {
  content: none !important;
}

a {
  color: var(--link);
}

a:hover {
  color: var(--ink);
}

a:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 2px;
}

h1, h2, h3, h4,
.cover h1,
.toc-title,
.chapter-header,
.chapter-title,
.site-brand,
.part,
.lesson-header h2 {
  font-family: var(--mono) !important;
  letter-spacing: -0.01em;
  font-weight: 500 !important;
  text-transform: none;
}

.layout {
  max-width: none;
  width: 100%;
  margin: 0;
  padding: 0 var(--layout-pad) 3rem;
  box-sizing: border-box;
}
@media (min-width: 1100px) {
  .layout {
    grid-template-columns: auto minmax(0, 1fr);
    column-gap: var(--header-gap);
    transition: column-gap var(--dur) var(--ease-out);
  }
  .toc {
    top: calc(3.75rem + 0.65rem);
    max-height: calc(100vh - 4.5rem - 0.65rem);
    box-sizing: border-box;
    width: var(--sidebar);
    min-width: 0;
    overflow-x: hidden;
    overflow-y: auto;
    opacity: 1;
    transition:
      width var(--dur) var(--ease-out),
      opacity var(--dur) var(--ease-out),
      padding var(--dur) var(--ease-out),
      border-width var(--dur) var(--ease-out),
      margin var(--dur) var(--ease-out);
  }
  .layout.toc-collapsed { column-gap: 0; }
  .layout.toc-collapsed .toc {
    width: 0;
    opacity: 0;
    padding: 0 !important;
    border-width: 0 !important;
    margin: 0;
    overflow: hidden;
    pointer-events: none;
  }
}

.cover {
  max-width: none;
  width: 100%;
  padding: 3.25rem var(--layout-pad) 2rem !important;
  text-align: left !important;
}
.cover::before {
  content: "── notes ────────────────────────────────";
  display: block;
  margin-bottom: 1rem;
  color: var(--faint);
  font-size: 0.72rem;
  white-space: nowrap;
  overflow: hidden;
}
.cover h1 {
  background: none !important;
  -webkit-background-clip: unset !important;
  background-clip: unset !important;
  color: var(--ink) !important;
  text-shadow: none !important;
  font-size: clamp(1.8rem, 4.5vw, 2.6rem) !important;
  line-height: 1.1 !important;
  margin-bottom: 0.65rem !important;
}
.cover-sub,
.cover-meta {
  font-family: var(--mono);
  color: var(--muted) !important;
  max-width: 42rem;
}

.site-header {
  display: grid !important;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  column-gap: 0.75rem;
  row-gap: 0.4rem;
  padding-block: 0.55rem !important;
  padding-inline: var(--layout-pad) !important;
  background: color-mix(in srgb, var(--bg) 92%, transparent) !important;
  backdrop-filter: none;
  border-bottom: 1px solid var(--line) !important;
}
.header-left,
.header-center,
.header-right {
  display: flex;
  align-items: center;
  min-width: 0;
}
.header-left { gap: 0.45rem; grid-column: 1; grid-row: 1; }
.header-center { gap: 0.65rem; flex: 1 1 auto; grid-column: 1 / -1; grid-row: 2; }
.header-right { gap: 0.45rem; flex-wrap: wrap; justify-content: flex-end; grid-column: 2; grid-row: 1; }
@media (min-width: 1100px) {
  .site-header {
    grid-template-columns: var(--sidebar) minmax(0, 1fr) auto;
    column-gap: var(--header-gap);
  }
  .header-left { grid-column: 1; grid-row: 1; }
  .header-center { grid-column: 2; grid-row: 1; }
  .header-right { grid-column: 3; grid-row: 1; }
  .site-header.is-toc-collapsed {
    grid-template-columns: auto minmax(0, 1fr) auto;
  }
}
.site-header .site-brand {
  flex: 0 1 auto;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  text-decoration: none;
  color: var(--ink) !important;
  font-size: 0.88rem !important;
  font-weight: 500 !important;
}
.site-header .site-brand:hover {
  color: var(--muted) !important;
  text-decoration: none;
}
.site-header .reading-pos {
  display: none;
  flex: 1 1 auto;
  margin: 0;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  font-size: 0.75rem;
  color: var(--faint);
}
@media (min-width: 720px) {
  .site-header .reading-pos { display: block; }
}
.site-header .header-parts {
  display: none;
  gap: 0.75rem;
  flex-wrap: wrap;
  font-size: 0.75rem;
}
@media (min-width: 900px) {
  .site-header .header-parts { display: inline-flex; }
}
.site-header .header-parts a {
  color: var(--muted);
  text-decoration: none;
  font-weight: 400;
  border-bottom: 1px solid transparent;
}
.site-header .header-parts a:hover {
  color: var(--ink);
  border-color: var(--line-strong);
  text-decoration: none;
}

.toc-panel-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  margin: 0;
  padding: 0.35rem 0.7rem;
  border: 1px solid var(--line-strong);
  border-radius: 0;
  background: transparent;
  color: var(--ink);
  font: inherit;
  font-size: 0.75rem;
  font-weight: 500;
  line-height: 1.2;
  cursor: pointer;
  white-space: nowrap;
  box-shadow: none;
  transition: border-color var(--dur-fast) linear, color var(--dur-fast) linear, background var(--dur-fast) linear;
}
.toc-panel-toggle:hover {
  border-color: var(--ink);
  color: var(--ink);
  background: var(--surface-2);
}
.toc-panel-toggle:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 2px;
}
.toc-panel-toggle svg {
  display: block;
  width: 0.95rem;
  height: 0.95rem;
  flex: 0 0 auto;
}
.toc-panel-toggle.is-collapsed {
  color: var(--muted);
}
.toc-panel-toggle.is-collapsed:hover {
  color: var(--ink);
}

.book-switcher {
  --switch-pad: 0.12rem;
  --switch-i: 0;
  position: relative;
  display: inline-grid;
  grid-template-columns: 1fr 1fr;
  align-items: stretch;
  isolation: isolate;
  min-width: 10.5rem;
  padding: var(--switch-pad);
  border: 1px solid var(--line-strong);
  border-radius: 0;
  background: var(--surface);
  font-size: 0.72rem;
  box-shadow: none;
  overflow: hidden;
}
.book-switcher::before {
  content: "";
  position: absolute;
  z-index: 0;
  top: var(--switch-pad);
  left: var(--switch-pad);
  width: calc((100% - 2 * var(--switch-pad)) / 2);
  height: calc(100% - 2 * var(--switch-pad));
  border-radius: 0;
  background: var(--ink);
  transform: translateX(calc(var(--switch-i) * 100%));
  transition: transform var(--dur) var(--ease-out);
  pointer-events: none;
}
.book-switcher.is-switching::before {
  background: var(--muted);
}
.book-switcher.is-snap::before { transition: none; }
.book-switcher a {
  position: relative;
  z-index: 1;
  display: grid;
  place-items: center;
  margin: 0;
  padding: 0.32rem 0.65rem;
  border-radius: 0;
  color: var(--muted);
  text-decoration: none;
  line-height: 1.15;
  font-weight: 500;
  background: transparent;
  transition: color var(--dur) linear;
}
.book-switcher a:hover {
  color: var(--ink);
  text-decoration: none;
}
.book-switcher a.is-active,
.book-switcher a.is-active:hover {
  color: var(--bg);
  background: transparent;
}
.book-switcher a:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 2px;
}
.site-header .book-hub {
  color: var(--muted);
  font-size: 0.75rem;
  font-weight: 400;
  text-decoration: none;
  border-bottom: 1px solid transparent;
}
.site-header .book-hub:hover {
  color: var(--ink);
  border-color: var(--line-strong);
  text-decoration: none;
}

.toc {
  background: var(--surface) !important;
  border: 1px solid var(--line-strong) !important;
  border-radius: 0 !important;
  box-shadow: none !important;
}
.toc-title {
  color: var(--ink) !important;
  font-size: 0.88rem !important;
  font-weight: 500 !important;
}
.toc-sec {
  color: var(--faint) !important;
  font-weight: 500 !important;
  letter-spacing: 0.04em !important;
}
.toc-twist {
  flex: 0 0 auto;
  width: 0.95rem;
  height: 0.95rem;
  margin-top: 0.12rem;
  display: inline-grid;
  place-items: center;
  border-radius: 0;
  color: var(--faint);
  transition: transform var(--dur) linear, color var(--dur-fast) linear;
}
.toc-twist::before {
  content: "›";
  font-size: 0.9rem;
  line-height: 1;
  border: none;
  width: auto;
  height: auto;
  transform: none;
  translate: none;
}
.toc-part-sum:hover > .toc-twist,
.toc-chapter-sum:hover > .toc-twist {
  color: var(--ink);
}
details[open] > summary > .toc-twist {
  transform: rotate(90deg);
  color: var(--ink) !important;
}
.toc-part-sum {
  color: var(--ink) !important;
  font-weight: 500 !important;
}
.toc-chapter-sum {
  color: var(--muted) !important;
  font-weight: 400 !important;
}
.toc-chapter-label {
  color: var(--faint) !important;
}
.toc-part-sum:hover,
.toc-chapter-sum:hover {
  background: var(--surface-2) !important;
}
.toc-toolbar { flex-wrap: wrap; gap: 0.35rem 0.5rem; }
.toc-btn.toc-toggle {
  border: 1px solid var(--line) !important;
  background: transparent !important;
  color: var(--muted) !important;
  border-radius: 0 !important;
  box-shadow: none;
}
.toc-btn.toc-toggle:hover {
  background: var(--surface-2) !important;
  color: var(--ink) !important;
  border-color: var(--line-strong) !important;
}
.toc-list a {
  border-radius: 0 !important;
  transition: background var(--dur-fast) linear, color var(--dur-fast) linear, box-shadow var(--dur-fast) linear;
}
.toc-list a:hover { background: var(--surface-2) !important; }
.toc-list a.is-active {
  background: var(--surface-2) !important;
  color: var(--ink) !important;
  box-shadow: inset 1px 0 0 var(--accent) !important;
}
.toc-list a.is-active .toc-num { color: var(--accent) !important; }
.toc-num { font-size: 0.85em; color: var(--faint); }
li.toc-practice > a {
  border-left-color: var(--practice) !important;
  background: color-mix(in srgb, var(--practice) 6%, var(--surface)) !important;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}
.toc-search-wrap { flex: 1 1 100%; position: relative; }
.toc-search {
  width: 100%;
  box-sizing: border-box;
  border: 1px solid var(--line-strong);
  border-radius: 0;
  background: var(--bg);
  color: var(--ink);
  padding: 0.4rem 1.8rem 0.4rem 0.6rem;
  font: inherit;
  font-size: 0.8rem;
}
.toc-search::placeholder { color: var(--faint); }
.toc-search:focus {
  outline: none;
  border-color: var(--muted);
}
.toc-search-clear {
  position: absolute;
  right: 0.25rem;
  top: 50%;
  transform: translateY(-50%);
  border: none;
  background: transparent;
  color: var(--muted);
  cursor: pointer;
  font-size: 1rem;
  line-height: 1;
  padding: 0.2rem 0.3rem;
  border-radius: 0;
}
.toc-search-clear:hover { color: var(--ink); }
.toc-search-results {
  margin: 0.45rem 0 0.3rem;
  max-height: 14rem;
  overflow: auto;
  border: 1px solid var(--line-strong);
  border-radius: 0;
  background: var(--bg);
}
.toc-search-empty {
  margin: 0;
  padding: 0.6rem 0.7rem;
  color: var(--muted);
  font-size: 0.8rem;
}
.toc-search-hit {
  display: block;
  padding: 0.45rem 0.6rem;
  border-bottom: 1px solid var(--line);
  text-decoration: none;
  color: var(--ink);
}
.toc-search-hit:last-child { border-bottom: none; }
.toc-search-hit:hover {
  background: var(--surface-2);
  text-decoration: none;
}
.toc-search-hit-meta {
  display: block;
  font-size: 0.68rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--faint);
  margin-bottom: 0.1rem;
}
.toc-search-hit-title {
  display: block;
  font-size: 0.84rem;
  font-weight: 500;
  line-height: 1.3;
}
.toc-search-hit-snip {
  display: block;
  margin-top: 0.15rem;
  font-size: 0.74rem;
  color: var(--muted);
  line-height: 1.35;
}
.toc.is-filtering .toc-list li.toc-match > a {
  background: color-mix(in srgb, var(--amber) 8%, transparent);
}
.toc-btn.toc-toggle:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.progress-bar {
  height: 1px !important;
  background: var(--accent) !important;
}

.resume-banner {
  max-width: none;
  margin-inline: var(--layout-pad);
  background: var(--surface) !important;
  border: 1px solid var(--line-strong) !important;
  border-radius: 0 !important;
  box-shadow: none !important;
}
.resume-banner a { color: var(--accent) !important; }

.part {
  margin: 2.5rem 0 1.2rem !important;
  padding-bottom: 0.4rem !important;
  border-bottom: 1px solid var(--line) !important;
  color: var(--ink) !important;
  font-size: clamp(1.1rem, 2.4vw, 1.35rem) !important;
}
.chapter-header {
  margin: 1.6rem 0 1rem !important;
  padding: 0.75rem 0.9rem !important;
  border: 1px solid var(--line-strong) !important;
  border-radius: 0 !important;
  background: var(--surface) !important;
  box-shadow: none !important;
}
.chapter-meta {
  color: var(--faint) !important;
  font-weight: 500 !important;
  letter-spacing: 0.05em !important;
}
.chapter-title { color: var(--ink) !important; }

.lesson {
  background: var(--surface) !important;
  border: 1px solid var(--line) !important;
  border-radius: 0 !important;
  box-shadow: none !important;
  margin-bottom: 1.2rem !important;
}
.lesson-header {
  border-left: 1px solid var(--lesson-rail) !important;
  padding: 1rem 1.1rem 0.5rem !important;
}
.lesson-meta {
  color: var(--faint) !important;
  font-weight: 500 !important;
  letter-spacing: 0.05em !important;
}
.lesson-header h2 {
  color: var(--ink) !important;
  font-weight: 500 !important;
}
.lesson-body {
  max-width: none;
  padding: 0.2rem 1.1rem 1.05rem !important;
}
.lesson-body h3 {
  color: var(--ink) !important;
  font-size: 0.98rem !important;
}
.lesson-nav {
  border-top: 1px solid var(--line) !important;
  background: var(--bg) !important;
  font-size: 0.78rem !important;
}
.lesson-nav a:hover { color: var(--ink) !important; }
.nav-toc { color: var(--muted) !important; }

.lesson.practice {
  border-color: color-mix(in srgb, var(--practice) 35%, var(--line)) !important;
}
.lesson.practice .lesson-header {
  border-left-color: var(--practice) !important;
  background: color-mix(in srgb, var(--practice) 5%, transparent) !important;
}
.lesson.practice .lesson-meta { color: var(--practice) !important; }
.practice-body h4 { color: var(--practice) !important; }
.difficulty {
  border: 1px solid var(--line-strong);
  border-radius: 0 !important;
  background: var(--bg) !important;
  font-size: 0.72rem !important;
  color: var(--muted);
}
.difficulty-easy { color: var(--green) !important; border-color: color-mix(in srgb, var(--green) 35%, var(--line)); }
.difficulty-medium { color: var(--amber) !important; border-color: color-mix(in srgb, var(--amber) 35%, var(--line)); }
.difficulty-hard { color: var(--red) !important; border-color: color-mix(in srgb, var(--red) 35%, var(--line)); }

blockquote {
  border-left: 1px solid var(--line-strong) !important;
  background: var(--surface-2) !important;
  color: var(--muted) !important;
  border-radius: 0 !important;
}
th {
  background: var(--surface-2) !important;
  color: var(--muted) !important;
  font-weight: 500;
}
th, td { border-color: var(--line) !important; }
hr { border-color: var(--line) !important; }
.verse { border-left-color: var(--line) !important; }
dl.mapping,
ol.algo {
  background: var(--surface-2) !important;
  border: 1px solid var(--line) !important;
  border-radius: 0 !important;
}
strong.version { color: var(--accent) !important; }
.source { font-size: 0.74rem !important; color: var(--faint) !important; }

code {
  font-family: var(--mono) !important;
  color: var(--ink) !important;
  background: var(--surface-2) !important;
  border-radius: 0 !important;
  border: 1px solid var(--line);
}
pre {
  border: 1px solid var(--line-strong) !important;
  box-shadow: none !important;
  border-radius: 0 !important;
  background: var(--pre-bg) !important;
}
pre code {
  color: inherit !important;
  background: transparent !important;
  border: none !important;
}

.code-window {
  margin: 1em 0;
  border-radius: 0;
  border: 1px solid var(--line-strong);
  background: var(--pre-bg);
  overflow: hidden;
  box-shadow: none;
}
.code-window:hover {
  border-color: var(--muted);
}
.code-window-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  min-height: 1.75rem;
  padding: 0.15rem 0.35rem 0.15rem 0.65rem;
  border-bottom: 1px solid var(--line);
  background: var(--surface);
}
.code-lang {
  font-size: 0.68rem;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--faint);
  user-select: none;
}
.code-window pre {
  margin: 0 !important;
  border-radius: 0 !important;
  border: none !important;
  background: transparent !important;
  box-shadow: none !important;
}
.code-copy {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  margin: 0;
  padding: 0.2rem 0.45rem;
  border: 1px solid transparent;
  border-radius: 0;
  background: transparent;
  color: var(--faint);
  font: inherit;
  font-size: 0.68rem;
  font-weight: 500;
  cursor: pointer;
  transition: color var(--dur-fast) linear, border-color var(--dur-fast) linear;
}
.code-copy:hover {
  color: var(--ink);
  border-color: var(--line-strong);
}
.code-copy:focus-visible {
  outline: 1px solid var(--accent);
  outline-offset: 1px;
}
.code-copy.is-copied {
  color: var(--accent);
  border-color: color-mix(in srgb, var(--accent) 40%, var(--line));
}
.code-copy svg {
  display: block;
  width: 0.85rem;
  height: 0.85rem;
  flex: 0 0 auto;
}

.back-top {
  opacity: 0;
  visibility: hidden;
  transform: translate3d(0, 0.25rem, 0);
  pointer-events: none;
  border: 1px solid var(--line-strong) !important;
  background: var(--surface) !important;
  color: var(--ink) !important;
  box-shadow: none !important;
  border-radius: 0 !important;
  transition:
    opacity var(--dur) linear,
    transform var(--dur) linear,
    visibility var(--dur) linear;
}
.back-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translate3d(0, 0, 0);
  pointer-events: auto;
}
.back-top:hover {
  border-color: var(--ink) !important;
  color: var(--ink) !important;
}

.skip-link {
  background: var(--surface) !important;
  border: 1px solid var(--line-strong) !important;
  border-radius: 0 !important;
}

@keyframes guide-fade-in {
  from { opacity: 0; }
  to { opacity: 1; }
}

body.guide-animate .site-header,
body.guide-animate .cover,
body.guide-animate .layout {
  animation: guide-fade-in var(--dur-slow) var(--ease-out) both;
}

@media (max-width: 1099px) {
  .layout.toc-collapsed .toc { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  :root {
    --dur-fast: 0.01ms;
    --dur: 0.01ms;
    --dur-slow: 0.01ms;
  }
  body.guide-animate .site-header,
  body.guide-animate .cover,
  body.guide-animate .layout {
    animation: none !important;
  }
  .layout,
  .toc,
  .site-header,
  .back-top,
  .progress-bar,
  .toc-panel-toggle,
  .code-copy,
  .toc-list a,
  .book-switcher,
  .book-switcher::before,
  .book-switcher a {
    transition: none !important;
  }
}

.hljs { color: var(--pre-fg); background: transparent; }
.hljs-comment,
.hljs-quote { color: var(--faint); font-style: italic; }
.hljs-keyword,
.hljs-selector-tag,
.hljs-literal,
.hljs-section,
.hljs-link { color: var(--violet); }
.hljs-function .hljs-keyword { color: var(--violet); }
.hljs-subst { color: var(--ink); }
.hljs-string,
.hljs-title,
.hljs-name,
.hljs-type,
.hljs-attribute,
.hljs-symbol,
.hljs-bullet,
.hljs-addition,
.hljs-variable,
.hljs-template-tag,
.hljs-template-variable { color: var(--green); }
.hljs-title.function_,
.hljs-title.class_,
.hljs-title.class_.inherited__ { color: var(--sky); }
.hljs-number,
.hljs-built_in,
.hljs-builtin-name,
.hljs-params,
.hljs-meta,
.hljs-selector-id,
.hljs-selector-class,
.hljs-deletion { color: var(--amber); }
.hljs-regexp,
.hljs-attr { color: var(--accent); }
.hljs-emphasis { font-style: italic; }
.hljs-strong { font-weight: 700; }

@media print {
  body { background: #fff !important; }
  .book-switcher,
  .book-hub,
  .toc-search-wrap,
  .toc-search-results,
  .toc-twist,
  .toc-panel-toggle,
  .header-left,
  .code-window-bar,
  .cover::before { display: none !important; }
  .site-header { display: block !important; }
  .layout { padding: 0; }
  .layout.toc-collapsed .toc { display: block !important; }
  .code-window,
  .lesson,
  .chapter-header,
  .toc,
  pre { border-color: #ccc !important; box-shadow: none !important; }
}