@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&family=JetBrains+Mono:wght@400;500;600&display=swap');

/* ==========================================================================
   sciencekit — mdBook theme inspired by the voxt.actnow.dev design system
   Light + dark palettes driven by CSS variables (mdBook body classes:
   light/rust → light · coal/navy/ayu → dark). Dark is the book default.
   ========================================================================== */

:root {
  /* Light palette (default) */
  --sk-bg: #ffffff;
  --sk-wash-1: rgba(2, 132, 199, 0.05);
  --sk-wash-2: rgba(124, 58, 237, 0.05);
  --sk-bg-subtle: #f6f7f9;
  --sk-bg-muted: rgba(15, 23, 42, 0.035);
  --sk-surface: linear-gradient(180deg, rgba(255, 255, 255, 0.96), rgba(248, 249, 250, 0.9));
  --sk-surface-solid: #ffffff;
  --sk-fg: #18181b;
  --sk-fg-body: #303036;
  --sk-fg-strong: #09090b;
  --sk-muted-fg: #52525c;
  --sk-border: rgba(15, 23, 42, 0.14);
  --sk-border-soft: rgba(15, 23, 42, 0.09);
  --sk-stripe: rgba(246, 247, 249, 0.55);
  --sk-code-bg: rgba(15, 23, 42, 0.05);
  --sk-codeblock-bg: #fbfcfd;
  --sk-donut-track: #eceef1;
  --sk-dot: rgba(15, 23, 42, 0.16);
  --sk-sidebar-bg: rgba(250, 251, 252, 0.92);
  --sk-shadow: 0 18px 40px -28px rgba(15, 23, 42, 0.45);
  --sk-shadow-lg: 0 28px 90px -54px rgba(15, 23, 42, 0.42);

  --sk-sky: #0284c7;
  --sk-sky-bg: rgba(2, 132, 199, 0.09);
  --sk-violet: #7c3aed;
  --sk-violet-bg: rgba(124, 58, 237, 0.1);
  --sk-emerald: #059669;
  --sk-emerald-bg: rgba(5, 150, 105, 0.1);
  --sk-amber: #b45309;
  --sk-amber-bg: rgba(217, 119, 6, 0.11);
  --sk-rose: #e11d48;
  --sk-rose-bg: rgba(225, 29, 72, 0.08);

  --sk-radius-sm: 10px;
  --sk-radius: 14px;
  --sk-radius-lg: 22px;
  --sk-font-sans: 'Inter', 'Helvetica Neue', Arial, sans-serif;
  --sk-font-mono: 'JetBrains Mono', SFMono-Regular, Consolas, Menlo, monospace;
}

/* Dark palette — Voxt dark tokens (bg #09090b, card #151518, border white/12).
   mdBook 0.5 sets the theme class on <html>. Only Light and Dark are exposed;
   coal/navy/ayu all map to the same dark palette for safety. */
html.coal body,
html.navy body,
html.ayu body {
  --sk-bg: #0b0b0e;
  --sk-wash-1: rgba(56, 189, 248, 0.06);
  --sk-wash-2: rgba(167, 139, 250, 0.07);
  --sk-bg-subtle: #16161a;
  --sk-bg-muted: rgba(255, 255, 255, 0.07);
  --sk-surface: linear-gradient(180deg, rgba(30, 30, 35, 0.92), rgba(22, 22, 26, 0.95));
  --sk-surface-solid: #1b1b1f;
  --sk-fg: #f4f4f5;
  --sk-fg-body: #e6e6ea;
  --sk-fg-strong: #fafafa;
  --sk-muted-fg: #a8a8b3;
  --sk-border: rgba(255, 255, 255, 0.18);
  --sk-border-soft: rgba(255, 255, 255, 0.11);
  --sk-stripe: rgba(255, 255, 255, 0.04);
  --sk-code-bg: rgba(255, 255, 255, 0.09);
  --sk-codeblock-bg: #141417;
  --sk-donut-track: #26262c;
  --sk-dot: rgba(255, 255, 255, 0.13);
  --sk-sidebar-bg: rgba(14, 14, 17, 0.94);
  --sk-shadow: 0 18px 40px -24px rgba(0, 0, 0, 0.6);
  --sk-shadow-lg: 0 28px 90px -48px rgba(0, 0, 0, 0.65);

  --sk-sky: #4cc2ff;
  --sk-violet: #b39bff;
  --sk-emerald: #3ddc97;
  --sk-amber: #ffc94d;
  --sk-rose: #ff8095;
}

/* Normalize the root font size (mdBook's variables.css sets :root to 10px).
   :root equals its specificity; our stylesheet loads later and wins.
   16px equals 12pt — the body scale below keeps prose at that size while
   headings step proportionally. html[data-sk-font-scale] (set by custom.js)
   moves prose across a bounded range without breaking KaTeX or Mermaid. */
:root {
  font-size: 16px;
  scroll-behavior: smooth;
  --sk-prose-scale: 1;
}

html[data-sk-font-scale="1"] { --sk-prose-scale: 1.06; }
html[data-sk-font-scale="2"] { --sk-prose-scale: 1.12; }

.content p,
.content li {
  font-size: calc(0.9375rem * var(--sk-prose-scale));
}

body {
  font-family: var(--sk-font-sans);
  color: var(--sk-fg);
  background:
    radial-gradient(circle at top left, var(--sk-wash-1), transparent 30%),
    radial-gradient(circle at top right, var(--sk-wash-2), transparent 30%),
    var(--sk-bg);
  -webkit-font-smoothing: antialiased;
}

/* --------------------------------------------------------------------------
   Layout
   -------------------------------------------------------------------------- */

.content {
  overflow-y: visible;
}

.content main {
  max-width: min(62rem, 100%);
  min-width: 0;
  margin: 0 auto;
  padding-left: 3rem;
  padding-right: 3rem;
}

@media only screen and (max-width: 1100px) {
  .content main {
    padding-left: 1.6rem;
    padding-right: 1.6rem;
  }
}

.page {
  border-left: none;
  background: transparent;
}

/* --------------------------------------------------------------------------
   Top menu bar — ghost icon buttons
   -------------------------------------------------------------------------- */

.menu-bar,
#mdbook-menu-bar-hover-placeholder,
#menu-bar-hover-placeholder {
  background: transparent;
  border-bottom: none;
}

.menu-bar {
  position: relative;
  z-index: 20;
}

/* Ghost controls: no boxed border, transparent ground, soft hover wash.
   Keeps the bar visually quiet next to the content buttons below. */
.menu-bar .icon-button {
  border: none;
  background: transparent;
  color: var(--sk-muted-fg);
  border-radius: 8px;
  transition: background 0.15s ease, color 0.15s ease;
}

.menu-bar .icon-button:hover {
  background: var(--sk-bg-muted);
  color: var(--sk-fg-strong);
}

.menu-bar .icon-button:focus-visible {
  outline: 2px solid var(--sk-sky);
  outline-offset: 1px;
}

.menu-bar .icon-button:disabled {
  opacity: 0.35;
  cursor: default;
}

/* Font-size control group injected by custom.js (A- / A / A+). */
.menu-bar .sk-font-group {
  display: inline-flex;
  align-items: center;
  gap: 2px;
  margin-left: 0.35rem;
  padding-left: 0.5rem;
  border-left: 1px solid var(--sk-border-soft);
}

.menu-bar .sk-font-btn {
  font-family: var(--sk-font-sans);
  font-weight: 650;
  font-size: 0.8rem;
  min-width: 1.9rem;
  letter-spacing: 0;
}

.menu-bar i,
.menu-bar .fa-svg svg {
  color: inherit;
}

/* --------------------------------------------------------------------------
   Sidebar
   -------------------------------------------------------------------------- */

.sidebar {
  background: var(--sk-sidebar-bg);
  backdrop-filter: blur(10px);
  border-right: 1px solid var(--sk-border-soft);
  /* Width MUST follow mdBook's variable: book.js drives resizing by setting
     --sidebar-target-width on <html> (consumed via --sidebar-width), and the
     content wrapper is offset by the same variable. A fixed width here
     silently disables the resize handle. */
  width: var(--sidebar-width);
}

.sidebar .brand {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  padding: 1.35rem 1.25rem 0.9rem;
}

.sidebar .brand-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 34px;
  height: 34px;
  border-radius: 11px;
  background: linear-gradient(135deg, #18181b, #334155);
  color: #fff;
  font-weight: 800;
  font-size: 0.95rem;
  letter-spacing: -0.03em;
  box-shadow: var(--sk-shadow);
  flex-shrink: 0;
}

html.coal body .brand-mark,
html.navy body .brand-mark,
html.ayu body .brand-mark {
  background: linear-gradient(135deg, #e4e4e7, #a1a1aa);
  color: #0b0b0e;
}

.sidebar .brand-name {
  font-weight: 700;
  font-size: 1.02rem;
  letter-spacing: -0.02em;
  color: var(--sk-fg-strong);
  line-height: 1.15;
}

.sidebar .brand-tagline {
  display: block;
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--sk-muted-fg);
  margin-top: 2px;
}

.sidebar-scrollbox {
  padding: 0.4rem 0.75rem 1.5rem;
}

.sidebar ol.chapter {
  padding: 0;
}

.sidebar li.part-title {
  margin: 1.4rem 0 0.45rem;
  padding: 0 0.75rem;
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--sk-muted-fg);
  opacity: 0.8;
}

.sidebar ol.chapter > li > a,
.sidebar ol.section > li > a {
  display: block;
  padding: 0.44rem 0.75rem;
  margin: 0.1rem 0;
  border-radius: var(--sk-radius-sm);
  color: var(--sk-fg-body);
  font-size: 0.885rem;
  font-weight: 450;
  transition: background 0.15s ease, color 0.15s ease;
}

.sidebar ol.chapter > li > a:hover {
  background: var(--sk-bg-muted);
  color: var(--sk-fg-strong);
  text-decoration: none;
}

.sidebar ol.chapter > li.active > a,
.sidebar ol.chapter > li > a.active {
  background: var(--sk-violet-bg);
  color: var(--sk-violet);
  font-weight: 600;
}

/* Accordion: toggle affordance injected by custom.js. Collapsed sections
   hide their nested list; the toggle chevron rotates. Without JavaScript
   no toggle exists and every section stays visible. */
.sidebar li.chapter-item {
  position: relative;
}

.sidebar .sk-section-toggle {
  position: absolute;
  right: 0.35rem;
  top: 0.28rem;
  width: 1.6rem;
  height: 1.6rem;
  padding: 0;
  border: none;
  border-radius: 6px;
  background: transparent;
  color: var(--sk-muted-fg);
  cursor: pointer;
  line-height: 1;
}

.sidebar .sk-section-toggle:hover {
  background: var(--sk-bg-muted);
  color: var(--sk-fg-strong);
}

.sidebar .sk-section-toggle::before {
  content: '▾';
  font-size: 0.75rem;
}

.sidebar li.chapter-item.sk-collapsed > .sk-section-toggle::before {
  content: '▸';
}

.sidebar li.chapter-item.sk-collapsed > ol.section {
  display: none;
}

.sidebar li.chapter-item > ol.section {
  overflow: hidden;
}

/* --------------------------------------------------------------------------
   Content typography
   -------------------------------------------------------------------------- */

.content h1 {
  font-size: calc(2.1rem * var(--sk-prose-scale));
  line-height: 1.15;
  font-weight: 800;
  letter-spacing: -0.035em;
  color: var(--sk-fg-strong);
  margin-top: 2.6rem;
  padding-bottom: 0.55em;
}

.content h2 {
  font-size: calc(1.45rem * var(--sk-prose-scale));
  font-weight: 700;
  letter-spacing: -0.025em;
  margin-top: 2.6rem;
  color: var(--sk-fg-strong);
}

.content h3 {
  font-size: calc(1.12rem * var(--sk-prose-scale));
  font-weight: 650;
  letter-spacing: -0.02em;
  margin-top: 2rem;
  color: var(--sk-fg-strong);
}

.content h4 {
  font-size: calc(1.02rem * var(--sk-prose-scale));
  font-weight: 600;
  color: var(--sk-fg-strong);
}

.content p,
.content li {
  color: var(--sk-fg-body);
  line-height: 1.75;
}

.content strong {
  color: var(--sk-fg-strong);
  font-weight: 650;
}

.content a {
  color: var(--sk-sky);
  text-decoration-color: color-mix(in srgb, var(--sk-sky) 40%, transparent);
  text-underline-offset: 3px;
}

.content a:hover {
  filter: brightness(1.15);
}

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

/* --------------------------------------------------------------------------
   Tables
   -------------------------------------------------------------------------- */

.content table {
  width: 100%;
  margin: 1.5rem 0;
  border-collapse: separate;
  border-spacing: 0;
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius);
  overflow: hidden;
  box-shadow: var(--sk-shadow);
  font-size: 0.92rem;
}

.content table thead th {
  background: var(--sk-bg-subtle);
  text-align: left;
  font-weight: 650;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  color: var(--sk-muted-fg);
  padding: 0.7rem 1rem;
  border-bottom: 1px solid var(--sk-border-soft);
}

.content table tbody td {
  padding: 0.68rem 1rem;
  border-bottom: 1px solid var(--sk-border-soft);
  vertical-align: top;
}

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

.content table tbody tr:nth-child(even) {
  background: var(--sk-stripe);
}

/* --------------------------------------------------------------------------
   Code
   -------------------------------------------------------------------------- */

code,
pre {
  font-family: var(--sk-font-mono);
}

:not(pre) > code {
  background: var(--sk-code-bg);
  border: 1px solid var(--sk-border-soft);
  border-radius: 7px;
  padding: 0.13em 0.42em;
  font-size: 0.84em;
  color: var(--sk-fg-strong);
  font-weight: 500;
}

pre code,
pre.code-wrapper pre {
  background: var(--sk-codeblock-bg);
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius);
  box-shadow: var(--sk-shadow);
  font-size: 0.86rem;
  line-height: 1.7;
}

pre.code-wrapper {
  margin: 1.4rem 0;
}

/* Playground buttons */
.playground .fa-svg svg,
button.copy-button svg {
  color: var(--sk-muted-fg);
}

/* --------------------------------------------------------------------------
   Buttons
   -------------------------------------------------------------------------- */

.sk-btn-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.8rem 0;
}

a.sk-btn,
span.sk-btn-static {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  height: 36px;
  padding: 0 16px;
  border-radius: 10px;
  font-size: 0.85rem;
  font-weight: 550;
  letter-spacing: -0.01em;
  transition: transform 0.15s ease, box-shadow 0.15s ease, background 0.15s ease;
  white-space: nowrap;
}

a.sk-btn:hover {
  transform: translateY(-1px);
  text-decoration: none;
}

a.sk-btn:active {
  transform: translateY(0);
}

a.sk-btn--primary {
  background: var(--sk-fg-strong);
  color: var(--sk-bg) !important;
  box-shadow: var(--sk-shadow);
}

a.sk-btn--primary:hover {
  filter: brightness(1.25);
  color: var(--sk-bg) !important;
}

html.coal body a.sk-btn--primary,
html.navy body a.sk-btn--primary,
html.ayu body a.sk-btn--primary {
  color: #0b0b0e !important;
}

a.sk-btn--secondary {
  background: color-mix(in srgb, var(--sk-surface-solid) 90%, transparent);
  border: 1px solid var(--sk-border-soft);
  color: var(--sk-fg) !important;
  box-shadow: none;
}

a.sk-btn--secondary:hover {
  background: var(--sk-bg-subtle);
}

a.sk-btn--star {
  background: linear-gradient(135deg, #b45309, #d97706);
  color: #fff !important;
  box-shadow: 0 14px 34px -18px rgba(180, 83, 9, 0.6);
}

a.sk-btn--star:hover {
  filter: brightness(1.06);
}

/* --------------------------------------------------------------------------
   Pills
   -------------------------------------------------------------------------- */

.sk-pill {
  display: inline-block;
  padding: 0.22em 0.85em;
  border-radius: 999px;
  font-size: 0.73rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  line-height: 1.5;
  vertical-align: middle;
}

.sk-pill--sky { background: var(--sk-sky-bg); color: var(--sk-sky); }
.sk-pill--violet { background: var(--sk-violet-bg); color: var(--sk-violet); }
.sk-pill--emerald { background: var(--sk-emerald-bg); color: var(--sk-emerald); }
.sk-pill--amber { background: var(--sk-amber-bg); color: var(--sk-amber); }
.sk-pill--rose { background: var(--sk-rose-bg); color: var(--sk-rose); }
.sk-pill--neutral { background: var(--sk-bg-muted); color: var(--sk-muted-fg); }

.sk-announce {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  background: var(--sk-bg-muted);
  border: 1px solid var(--sk-border-soft);
  border-radius: 999px;
  padding: 0.32rem 1rem 0.32rem 0.38rem;
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--sk-muted-fg);
  box-shadow: var(--sk-shadow);
}

.sk-announce__tag {
  background: var(--sk-fg-strong);
  color: var(--sk-bg);
  text-transform: uppercase;
  font-size: 0.64rem;
  font-weight: 700;
  letter-spacing: 0.09em;
  border-radius: 999px;
  padding: 0.3em 0.8em;
}

html.coal body .sk-announce__tag,
html.navy body .sk-announce__tag,
html.ayu body .sk-announce__tag {
  color: #0b0b0e;
}

/* --------------------------------------------------------------------------
   Hero
   -------------------------------------------------------------------------- */

.sk-hero {
  text-align: center;
  padding: 3.2rem 0 1.6rem;
  position: relative;
}

.sk-hero::before {
  content: '';
  position: absolute;
  inset: -1rem -20%;
  background-image: radial-gradient(circle, var(--sk-dot) 1px, transparent 1px);
  background-size: 17px 17px;
  mask-image: radial-gradient(ellipse 70% 62% at 50% 32%, black 26%, transparent 74%);
  -webkit-mask-image: radial-gradient(ellipse 70% 62% at 50% 32%, black 26%, transparent 74%);
  pointer-events: none;
  z-index: 0;
}

.sk-hero > * {
  position: relative;
  z-index: 1;
}

.sk-hero__title {
  font-size: clamp(2.5rem, 6vw, 3.9rem);
  line-height: 1.06;
  font-weight: 800;
  letter-spacing: -0.042em;
  color: var(--sk-fg-strong);
  margin: 1.5rem auto 1.1rem;
  max-width: 21ch;
  text-wrap: balance;
}

.sk-hero__subtitle {
  font-size: 1.08rem;
  line-height: 1.75;
  color: var(--sk-muted-fg);
  max-width: 46rem;
  margin: 0 auto;
  text-wrap: balance;
}

/* --------------------------------------------------------------------------
   Stats band
   -------------------------------------------------------------------------- */

.sk-stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1px;
  background: var(--sk-border-soft);
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius-lg);
  overflow: hidden;
  margin: 2.6rem 0;
  box-shadow: var(--sk-shadow);
}

.sk-stats__item {
  background: var(--sk-surface);
  backdrop-filter: blur(6px);
  padding: 1.5rem 1.2rem;
  text-align: center;
}

.sk-stats__value {
  font-size: 1.95rem;
  font-weight: 800;
  letter-spacing: -0.04em;
  color: var(--sk-fg-strong);
  line-height: 1.1;
}

.sk-stats__label {
  display: block;
  margin-top: 0.35rem;
  font-size: 0.78rem;
  font-weight: 550;
  color: var(--sk-muted-fg);
  letter-spacing: 0.01em;
}

/* --------------------------------------------------------------------------
   Cards
   -------------------------------------------------------------------------- */

.sk-cards {
  display: grid;
  gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  margin: 1.6rem 0;
}

.sk-cards--wide {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.sk-card {
  background: var(--sk-surface);
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius-lg);
  padding: 1.35rem 1.3rem;
  box-shadow: var(--sk-shadow);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.sk-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--sk-shadow-lg);
}

.sk-card__icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 42px;
  height: 42px;
  border-radius: 13px;
  font-size: 1.25rem;
  margin-bottom: 0.9rem;
}

.sk-card__title {
  font-size: 1.01rem;
  font-weight: 650;
  letter-spacing: -0.015em;
  color: var(--sk-fg-strong);
  margin-bottom: 0.45rem;
}

.sk-card p {
  font-size: 0.89rem;
  line-height: 1.65;
  color: var(--sk-muted-fg);
  margin: 0;
}

.sk-icon--sky { background: var(--sk-sky-bg); color: var(--sk-sky); }
.sk-icon--violet { background: var(--sk-violet-bg); color: var(--sk-violet); }
.sk-icon--emerald { background: var(--sk-emerald-bg); color: var(--sk-emerald); }
.sk-icon--amber { background: var(--sk-amber-bg); color: var(--sk-amber); }
.sk-icon--rose { background: var(--sk-rose-bg); color: var(--sk-rose); }
.sk-icon--neutral { background: var(--sk-bg-muted); color: var(--sk-fg); }

.sk-card--flow {
  background:
    radial-gradient(circle at top left, var(--sk-wash-1), transparent 42%),
    var(--sk-surface);
}

/* --------------------------------------------------------------------------
   Callout boxes
   -------------------------------------------------------------------------- */

.sk-box {
  position: relative;
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius);
  padding: 1.05rem 1.25rem 1.05rem 3.15rem;
  margin: 1.5rem 0;
  background: var(--sk-surface);
  box-shadow: var(--sk-shadow);
  font-size: 0.93rem;
}

.sk-box::before {
  position: absolute;
  left: 1.15rem;
  top: 50%;
  transform: translateY(-50%);
  font-size: 1.05rem;
  line-height: 1;
}

.sk-box p:last-child {
  margin-bottom: 0;
}

.sk-box--info::before { content: 'ℹ'; }
.sk-box--info { border-left: 3px solid var(--sk-sky); }
.sk-box--info strong:first-child { color: var(--sk-sky); }

.sk-box--tip::before { content: '💡'; }
.sk-box--tip { border-left: 3px solid var(--sk-violet); }

.sk-box--success::before { content: '✓'; font-weight: 800; color: var(--sk-emerald); }
.sk-box--success { border-left: 3px solid var(--sk-emerald); }

.sk-box--warning::before { content: '⚠'; color: var(--sk-amber); }
.sk-box--warning { border-left: 3px solid var(--sk-amber); }

.sk-box--danger::before { content: '✕'; font-weight: 800; color: var(--sk-rose); }
.sk-box--danger { border-left: 3px solid var(--sk-rose); }

/* --------------------------------------------------------------------------
   Statement panel
   -------------------------------------------------------------------------- */

.sk-statement {
  border: 1px solid var(--sk-border-soft);
  border-radius: 26px;
  padding: clamp(2rem, 5vw, 3.6rem);
  margin: 2.6rem 0;
  background:
    radial-gradient(circle at top left, var(--sk-wash-2), transparent 30%),
    radial-gradient(circle at bottom right, var(--sk-wash-1), transparent 30%),
    var(--sk-surface);
  box-shadow: var(--sk-shadow);
  text-align: center;
}

.sk-statement__text {
  font-size: clamp(1.6rem, 3.6vw, 2.5rem);
  font-weight: 750;
  letter-spacing: -0.035em;
  line-height: 1.22;
  color: var(--sk-fg-strong);
  margin: 0;
  text-wrap: balance;
}

/* --------------------------------------------------------------------------
   Progress bars
   -------------------------------------------------------------------------- */

.sk-progress {
  background: var(--sk-bg-muted);
  border-radius: 999px;
  height: 10px;
  overflow: hidden;
  margin: 0.55rem 0 0.3rem;
}

.sk-progress__bar {
  height: 100%;
  border-radius: 999px;
  min-width: 10px;
  position: relative;
  transition: width 0.9s cubic-bezier(0.22, 1, 0.36, 1);
}

.sk-progress__bar--sky { background: linear-gradient(90deg, #0ea5e9, #0284c7); }
.sk-progress__bar--violet { background: linear-gradient(90deg, #a78bfa, #7c3aed); }
.sk-progress__bar--emerald { background: linear-gradient(90deg, #34d399, #059669); }
.sk-progress__bar--amber { background: linear-gradient(90deg, #fbbf24, #d97706); }

.sk-progress__meta {
  display: flex;
  justify-content: space-between;
  font-size: 0.76rem;
  font-weight: 550;
  color: var(--sk-muted-fg);
}

/* --------------------------------------------------------------------------
   Timeline
   -------------------------------------------------------------------------- */

.sk-timeline {
  position: relative;
  margin: 2.2rem 0;
  padding-left: 2rem;
}

.sk-timeline::before {
  content: '';
  position: absolute;
  left: 8px;
  top: 6px;
  bottom: 6px;
  width: 2px;
  background: linear-gradient(180deg, var(--sk-sky), var(--sk-violet), var(--sk-emerald));
  opacity: 0.4;
  border-radius: 2px;
}

.sk-timeline__item {
  position: relative;
  margin-bottom: 1.4rem;
}

.sk-timeline__item::before {
  content: '';
  position: absolute;
  left: calc(-2rem + 3px);
  top: 0.55rem;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--sk-bg);
  border: 3px solid var(--sk-violet);
  box-shadow: 0 0 0 4px var(--sk-violet-bg);
}

.sk-timeline__item.is-done::before { border-color: var(--sk-emerald); box-shadow: 0 0 0 4px var(--sk-emerald-bg); }
.sk-timeline__item.is-active::before { border-color: var(--sk-amber); box-shadow: 0 0 0 4px var(--sk-amber-bg); }

.sk-timeline__card {
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius);
  background: var(--sk-surface);
  box-shadow: var(--sk-shadow);
  padding: 1.1rem 1.25rem;
}

.sk-timeline__head {
  display: flex;
  align-items: baseline;
  gap: 0.7rem;
  flex-wrap: wrap;
  margin-bottom: 0.35rem;
}

.sk-timeline__title {
  font-size: 1.02rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--sk-fg-strong);
}

/* --------------------------------------------------------------------------
   Donut chart
   -------------------------------------------------------------------------- */

.sk-donut-wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 2rem;
  justify-content: center;
  margin: 2rem 0;
  padding: 1.8rem;
  border: 1px solid var(--sk-border-soft);
  border-radius: 24px;
  background: var(--sk-surface);
  box-shadow: var(--sk-shadow);
}

.sk-donut {
  position: relative;
  width: 210px;
  height: 210px;
  flex-shrink: 0;
}

.sk-donut svg {
  width: 100%;
  height: 100%;
  transform: rotate(-90deg);
}

.sk-donut circle {
  fill: none;
  stroke-width: 27;
}

.sk-donut__center {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  pointer-events: none;
}

.sk-donut__value {
  font-size: 2.1rem;
  font-weight: 800;
  letter-spacing: -0.04em;
  color: var(--sk-fg-strong);
  line-height: 1;
}

.sk-donut__label {
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--sk-muted-fg);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-top: 0.3rem;
}

.sk-donut__legend {
  list-style: none;
  margin: 0;
  padding: 0;
  columns: 2;
  column-gap: 2rem;
  font-size: 0.85rem;
}

.sk-donut__legend li {
  break-inside: avoid;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.42rem;
  color: var(--sk-fg-body);
}

.sk-donut__swatch {
  width: 11px;
  height: 11px;
  border-radius: 4px;
  flex-shrink: 0;
}

.sk-donut__count {
  margin-left: auto;
  font-weight: 650;
  color: var(--sk-muted-fg);
  font-variant-numeric: tabular-nums;
}

/* --------------------------------------------------------------------------
   Horizontal bars
   -------------------------------------------------------------------------- */

.sk-bars {
  margin: 1.6rem 0;
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius-lg);
  padding: 1.4rem 1.5rem;
  background: var(--sk-surface);
  box-shadow: var(--sk-shadow);
}

.sk-bars__row {
  display: grid;
  grid-template-columns: 190px 1fr 52px;
  align-items: center;
  gap: 0.9rem;
  margin-bottom: 0.7rem;
  font-size: 0.85rem;
}

.sk-bars__row:last-child { margin-bottom: 0; }

.sk-bars__label {
  font-weight: 550;
  color: var(--sk-fg-body);
  text-align: right;
}

.sk-bars__track {
  background: var(--sk-bg-muted);
  border-radius: 999px;
  height: 14px;
  overflow: hidden;
}

.sk-bars__fill {
  height: 100%;
  border-radius: 999px;
  transition: width 0.9s cubic-bezier(0.22, 1, 0.36, 1);
}

.sk-bars__value {
  font-weight: 650;
  color: var(--sk-muted-fg);
  font-variant-numeric: tabular-nums;
}

/* --------------------------------------------------------------------------
   CTA
   -------------------------------------------------------------------------- */

.sk-cta {
  border: 1px solid var(--sk-border-soft);
  border-radius: 28px;
  padding: clamp(2rem, 5vw, 3.4rem);
  margin: 2.8rem 0;
  text-align: center;
  background:
    radial-gradient(circle at top left, rgba(217, 119, 6, 0.09), transparent 34%),
    radial-gradient(circle at top right, var(--sk-wash-2), transparent 34%),
    var(--sk-surface);
  box-shadow: var(--sk-shadow-lg);
}

.sk-cta__title {
  font-size: clamp(1.7rem, 4vw, 2.5rem);
  font-weight: 800;
  letter-spacing: -0.035em;
  color: var(--sk-fg-strong);
  margin-bottom: 0.7rem;
  text-wrap: balance;
}

.sk-cta p {
  color: var(--sk-muted-fg);
  max-width: 40rem;
  margin: 0 auto 1.4rem;
}

/* --------------------------------------------------------------------------
   Terminal window
   -------------------------------------------------------------------------- */

.sk-window {
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius-lg);
  overflow: hidden;
  box-shadow: var(--sk-shadow-lg);
  margin: 1.8rem 0;
  background: var(--sk-codeblock-bg);
}

.sk-window__bar {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.7rem 1rem;
  background: var(--sk-bg-subtle);
  border-bottom: 1px solid var(--sk-border-soft);
}

.sk-window__dot {
  width: 11px;
  height: 11px;
  border-radius: 50%;
}

.sk-window__dot--r { background: #f87171; }
.sk-window__dot--y { background: #fbbf24; }
.sk-window__dot--g { background: #34d399; }

.sk-window__title {
  margin-left: 0.5rem;
  font-size: 0.76rem;
  font-weight: 550;
  color: var(--sk-muted-fg);
  font-family: var(--sk-font-mono);
}

.sk-window pre {
  margin: 0 !important;
  border: none !important;
  border-radius: 0 !important;
  box-shadow: none !important;
  background: var(--sk-codeblock-bg) !important;
}

.sk-window .code-wrapper { margin: 0; }

/* --------------------------------------------------------------------------
   Bottom navigation & search
   -------------------------------------------------------------------------- */

.nav-wrapper {
  border-top: 1px solid var(--sk-border-soft);
  background: transparent;
}

.nav-wrapper a {
  color: var(--sk-muted-fg);
  font-weight: 500;
}

.nav-wrapper a:hover {
  color: var(--sk-fg-strong);
}

.nav-chapters li a:hover,
.nav-chapters a:hover {
  color: var(--sk-fg-strong);
}

#mdbook-searchbar,
#searchbar {
  border-radius: 999px;
  border: 1px solid var(--sk-border);
  padding: 0.45rem 1.1rem;
  font-family: var(--sk-font-sans);
  background: color-mix(in srgb, var(--sk-surface-solid) 90%, transparent);
  color: var(--sk-fg);
  box-shadow: var(--sk-shadow);
}

.popup {
  border-radius: var(--sk-radius-lg);
  border: 1px solid var(--sk-border-soft);
  box-shadow: var(--sk-shadow-lg);
  background: color-mix(in srgb, var(--sk-surface-solid) 97%, transparent);
  backdrop-filter: blur(10px);
}

/* --------------------------------------------------------------------------
   Mermaid diagrams — fixed-palette safety net + overflow handling
   -------------------------------------------------------------------------- */

.mermaid {
  margin: 1.6rem 0;
  padding: 1.25rem 1rem;
  border: 1px solid var(--sk-border-soft);
  border-radius: var(--sk-radius-lg);
  background: var(--sk-surface);
  box-shadow: var(--sk-shadow);
  overflow-x: auto;
  text-align: center;
}

.mermaid svg {
  max-width: 100%;
  height: auto;
  font-family: var(--sk-font-sans);
}

/* Mermaid renders node/edge labels as HTML (<p>/<span>) inside
   foreignObject. The book's own `.content p` rule matches those <p>
   elements directly, and a directly-matching rule always beats the
   per-node text colors Mermaid sets on ancestor spans — which is why
   diagram text rendered in body color (illegible on pastel fills in
   the dark theme). Restoring inheritance here wins by specificity
   (.mermaid svg p beats .content p) with no !important needed. */
.mermaid svg p,
.mermaid svg span {
  color: inherit;
}

/* Mermaid lays out foreignObject viewports assuming its own 13px label
   metrics, but it sets no inline font-size on the label elements — so the
   book's `.content p` rule (15px prose) matches the <p> tags directly and
   renders every label ~15% wider than measured, clipping text inside its
   viewport. Locking the size here restores the assumed metrics. */
.mermaid svg p {
  font-size: 13px;
  line-height: 1.5;
}

/* Fixed defaults for elements without explicit diagram styles: dark text
   on light fills plus neutral edges — identical in both book themes. */
.mermaid svg .node text,
.mermaid svg .nodeLabel,
.mermaid svg foreignObject div {
  color: #18181b;
  fill: #18181b;
}

.mermaid svg .flowchart-link {
  stroke: #52525c !important;
}

.mermaid svg .edgeLabel {
  color: #18181b;
}

.mermaid svg .edgeLabel rect,
.mermaid svg .edgeLabel foreignObject div {
  fill: #f4f4f5;
  background-color: #f4f4f5;
  color: #18181b;
}

/* Mermaid injects #id-scoped .labelBkg/.edgeLabel rules with 0.5 alpha;
   an opaque pill keeps dark edge text legible on both page themes. */
.mermaid svg .labelBkg {
  background-color: #f4f4f5 !important;
}

.mermaid svg .edgeLabel rect {
  opacity: 1 !important;
}

.mermaid svg .edgeLabel text {
  fill: #18181b;
}

.mermaid svg .cluster rect {
  fill: #f4f4f5 !important;
  stroke: #a8a8b3 !important;
}

.mermaid svg foreignObject div {
  white-space: normal;
  overflow-wrap: anywhere;
  line-height: 1.45;
}

/* --------------------------------------------------------------------------
   Reveal animations (custom.js adds .is-visible)
   -------------------------------------------------------------------------- */

.reveal {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 0.65s ease, transform 0.65s cubic-bezier(0.22, 1, 0.36, 1);
}

.reveal.is-visible {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  .reveal {
    opacity: 1;
    transform: none;
    transition: none;
  }
  html { scroll-behavior: auto; }
}