:root {
  --surface: #1a1a19;
  --surface-2: #201f1e;
  --surface-3: #262523;
  --line: #3c3c38;
  --line-soft: #2b2a28;
  --text: #e8e6df;
  --text-2: #c3c2b7;
  --muted: #8a8880;
  --accent: #3987e5;
  --warn: #c98500;
  --bad: #e66767;
  color-scheme: dark;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
  background: var(--surface);
  color: var(--text);
  font-family: ui-sans-serif, system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
  font-size: 15px;
  line-height: 1.6;
}

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

code,
pre,
.mono {
  font-family: ui-monospace, SFMono-Regular, 'SF Mono', Menlo, Consolas, monospace;
}

.app {
  display: flex;
  align-items: flex-start;
  min-height: 100vh;
}

/* ---------- sidebar ---------- */

.sidebar {
  position: sticky;
  top: 0;
  flex: 0 0 250px;
  height: 100vh;
  overflow-y: auto;
  padding: 20px 14px 24px 20px;
  border-right: 1px solid var(--line-soft);
  background: var(--surface-2);
}

.brand-title {
  font-size: 16px;
  font-weight: 600;
  letter-spacing: 0.01em;
}

.brand-sub {
  font-size: 12px;
  color: var(--muted);
  margin-bottom: 18px;
}

.nav-part-title {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  margin: 16px 0 4px;
}

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

.nav-item {
  display: flex;
  gap: 8px;
  align-items: baseline;
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  color: var(--text-2);
  padding: 4px 6px;
  border-radius: 5px;
  font: inherit;
  font-size: 13.5px;
  line-height: 1.35;
  cursor: pointer;
}

.nav-item:hover {
  background: var(--surface-3);
  color: var(--text);
}

.nav-item.active {
  background: var(--surface-3);
  color: var(--text);
  box-shadow: inset 2px 0 0 var(--accent);
}

.nav-num {
  display: inline-block;
  min-width: 14px;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
  font-size: 12px;
}

.nav-foot {
  margin-top: 26px;
  font-size: 11.5px;
  line-height: 1.5;
  color: var(--muted);
}

/* ---------- main column ---------- */

.main {
  flex: 1 1 auto;
  min-width: 0;
  padding: 28px 32px 80px;
}

.chapter {
  max-width: 860px;
  margin: 0 auto;
}

.chapter-part {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}

.chapter-head h2 {
  margin: 4px 0 6px;
  font-size: 25px;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.chapter-blurb {
  margin: 0 0 8px;
  color: var(--text-2);
}

.prose {
  max-width: 720px;
}

.prose h3 {
  font-size: 17px;
  margin: 26px 0 6px;
}

.prose p {
  margin: 12px 0;
}

.prose ul,
.prose ol {
  padding-left: 22px;
}

.prose li {
  margin: 5px 0;
}

.prose code {
  background: var(--surface-3);
  padding: 1px 4px;
  border-radius: 3px;
  font-size: 13px;
}

.prose blockquote {
  margin: 14px 0;
  padding: 2px 14px;
  border-left: 2px solid var(--line);
  color: var(--text-2);
}

.prose table {
  border-collapse: collapse;
  font-size: 13.5px;
  margin: 12px 0;
}

.prose th,
.prose td {
  border-bottom: 1px solid var(--line-soft);
  padding: 4px 12px 4px 0;
  text-align: left;
  font-variant-numeric: tabular-nums;
}

.katex-display {
  overflow-x: auto;
  overflow-y: hidden;
  padding: 2px 0;
}

/* ---------- labs ---------- */

.lab {
  margin: 24px 0 30px;
  padding: 14px 16px 16px;
  border: 1px solid var(--line-soft);
  border-radius: 8px;
  background: var(--surface-2);
}

.lab-head h3 {
  margin: 0;
  font-size: 15px;
  font-weight: 600;
}

.lab-caption {
  margin: 2px 0 0;
  font-size: 13px;
  color: var(--muted);
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 20px;
  margin: 12px 0 4px;
}

.control {
  display: flex;
  flex-direction: column;
  gap: 2px;
  font-size: 12px;
}

.control-toggle {
  flex-direction: row;
  align-items: center;
  gap: 6px;
}

.control-label {
  color: var(--muted);
}

.control-value {
  color: var(--text);
  font-variant-numeric: tabular-nums;
}

.control input[type='range'] {
  width: 150px;
  accent-color: var(--accent);
}

.control select {
  background: var(--surface-3);
  color: var(--text);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 2px 6px;
  font: inherit;
  font-size: 12.5px;
}

.lab-bar {
  display: flex;
  align-items: center;
  gap: 14px;
  margin: 10px 0 6px;
  flex-wrap: wrap;
}

.lab-bar-gap {
  flex: 1 1 auto;
}

button {
  font: inherit;
  font-size: 12.5px;
  padding: 3px 12px;
  border-radius: 5px;
  border: 1px solid var(--line);
  background: var(--surface-3);
  color: var(--text);
  cursor: pointer;
}

button:hover:not(:disabled) {
  border-color: var(--muted);
}

button:disabled {
  opacity: 0.5;
  cursor: default;
}

button.primary {
  background: #1c5cab;
  border-color: #256abf;
}

button.ghost {
  background: none;
  border-color: transparent;
  color: var(--muted);
}

button.ghost:hover {
  color: var(--text);
}

.stat {
  display: flex;
  flex-direction: column;
  line-height: 1.25;
}

.stat-label {
  font-size: 10.5px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.stat-value {
  font-size: 13px;
  font-variant-numeric: tabular-nums;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.warn {
  color: var(--warn);
  font-size: 12px;
}

.lab-error {
  color: var(--bad);
  background: #2a1d1d;
  border: 1px solid #4a2b2b;
  border-radius: 6px;
  padding: 8px 10px;
  font-size: 12.5px;
  white-space: pre-wrap;
  overflow-x: auto;
}

.lab-log {
  background: var(--surface-3);
  border-radius: 6px;
  padding: 8px 10px;
  font-size: 12px;
  max-height: 260px;
  overflow: auto;
  white-space: pre;
  color: var(--text-2);
}

.lab-placeholder {
  color: var(--muted);
  font-size: 13px;
  padding: 26px 0;
  text-align: center;
}

.lab-figures {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.figure-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.figure-row > * {
  flex: 1 1 320px;
  min-width: 300px;
}

.lab-editor {
  margin-top: 10px;
  border: 1px solid var(--line-soft);
  border-radius: 6px;
  overflow: hidden;
}

.lab-editor-bar {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 4px 8px;
  font-size: 12px;
  color: var(--muted);
  background: var(--surface-3);
}

.editor-host .cm-editor {
  max-height: 460px;
  font-size: 12.5px;
}

/* ---------- static figures ---------- */

.static-figure {
  margin: 22px 0;
  max-width: 720px;
}

.static-figure figcaption {
  margin-top: 8px;
  font-size: 12.5px;
  line-height: 1.5;
  color: var(--muted);
}

/* ---------- plots ---------- */

.plot-host {
  width: 100%;
}

.plot-title {
  font-size: 12px;
  color: var(--text-2);
  margin: 6px 0 -4px;
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 16px;
  font-size: 12px;
  color: var(--text-2);
  margin: -4px 0 6px 44px;
}

.legend-item {
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.legend-item.dim {
  opacity: 0.4;
}

.legend-value {
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

/* ---------- tables of numbers ---------- */

.numtable {
  border-collapse: collapse;
  font-size: 12.5px;
  font-variant-numeric: tabular-nums;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  margin: 4px 0 2px;
}

.numtable th {
  text-align: right;
  color: var(--muted);
  font-weight: 500;
  padding: 2px 10px 2px 0;
  border-bottom: 1px solid var(--line-soft);
}

.numtable td {
  text-align: right;
  padding: 1px 10px 1px 0;
}

/* ---------- library ---------- */

.lib-file {
  border-bottom: 1px solid var(--line-soft);
}

.lib-name {
  background: none;
  border: none;
  color: var(--text);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 13px;
  padding: 6px 0;
  cursor: pointer;
}

.lib-src {
  background: var(--surface-2);
  border-radius: 6px;
  padding: 10px 12px;
  font-size: 12.5px;
  overflow-x: auto;
  color: var(--text-2);
}

.pager {
  display: flex;
  max-width: 860px;
  margin: 30px auto 0;
  padding-top: 14px;
  border-top: 1px solid var(--line-soft);
}

@media (max-width: 900px) {
  .app {
    flex-direction: column;
  }

  .sidebar {
    position: static;
    width: 100%;
    height: auto;
    flex: none;
    border-right: none;
    border-bottom: 1px solid var(--line-soft);
  }

  .main {
    padding: 18px 14px 60px;
  }
}