/* Valence Shell Game — shared stylesheet.
   All theming via :root custom properties. Never hardcode colors in
   component rules. Subshell color law: s=cyan p=amber d=violet f=green. */

:root {
  /* backgrounds, darkest to lightest */
  --bg-deep: #060910;
  --bg-surface: #0b101c;
  --bg-elevated: #121a2b;
  --bg-hover: #182238;

  /* text */
  --text-primary: #e6ebf5;
  --text-secondary: #a8b3c9;
  --text-muted: #67748f;

  /* primary accents */
  --accent: #2dd4ed;        /* cyan — links, primary glow */
  --accent-2: #a78bfa;      /* violet — secondary */

  /* the subshell color law */
  --s-color: #2dd4ed;
  --p-color: #fbbf24;
  --d-color: #a78bfa;
  --f-color: #34d399;

  /* semantic (callouts, states) */
  --blue: #60a5fa;
  --green: #4ade80;
  --purple: #a78bfa;
  --amber: #fbbf24;
  --rose: #fb7185;

  /* rules */
  --rule: rgba(148, 168, 210, 0.12);
  --rule-strong: rgba(148, 168, 210, 0.26);

  /* fonts */
  --display: "Space Grotesk", system-ui, sans-serif;
  --sans: "Inter", system-ui, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, monospace;

  --sidebar-w: 260px;
  --content-max: 760px;
  --stage-max: 900px;
}

/* ---------- reset / base ---------- */

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  background: var(--bg-deep);
  color: var(--text-primary);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

::selection { background: rgba(45, 212, 237, 0.25); }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }

strong { color: var(--text-primary); }

/* ---------- subshell utilities ---------- */

.sub-s { color: var(--s-color); }
.sub-p { color: var(--p-color); }
.sub-d { color: var(--d-color); }
.sub-f { color: var(--f-color); }

.chip {
  display: inline-block;
  font-family: var(--mono);
  font-size: 13px;
  padding: 2px 9px;
  border-radius: 99px;
  border: 1px solid currentColor;
  background: color-mix(in srgb, currentColor 10%, transparent);
}
.chip.sub-s { box-shadow: 0 0 14px -4px var(--s-color); }
.chip.sub-p { box-shadow: 0 0 14px -4px var(--p-color); }
.chip.sub-d { box-shadow: 0 0 14px -4px var(--d-color); }
.chip.sub-f { box-shadow: 0 0 14px -4px var(--f-color); }

/* ---------- progress bar ---------- */

.progress-bar {
  position: fixed;
  top: 0; left: 0;
  height: 2px;
  width: 0;
  background: linear-gradient(90deg, var(--s-color), var(--d-color));
  box-shadow: 0 0 10px var(--accent);
  z-index: 100;
}

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

.sidebar {
  position: fixed;
  top: 0; left: 0;
  width: var(--sidebar-w);
  height: 100vh;
  padding: 36px 24px;
  background: var(--bg-surface);
  border-right: 1px solid var(--rule);
  overflow-y: auto;
  z-index: 50;
}

.sidebar-title {
  font-family: var(--display);
  font-size: 17px;
  font-weight: 600;
  letter-spacing: 0.01em;
  display: block;
  color: var(--text-primary);
  margin-bottom: 4px;
}
.sidebar-title:hover { text-decoration: none; color: var(--accent); }

.sidebar-eyebrow {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--text-muted);
  margin-bottom: 28px;
}

.toc { list-style: none; }

.toc a {
  display: block;
  padding: 6px 10px;
  margin: 1px 0;
  border-left: 2px solid transparent;
  border-radius: 0 6px 6px 0;
  font-size: 13.5px;
  color: var(--text-secondary);
  line-height: 1.4;
}
.toc a:hover { background: var(--bg-hover); text-decoration: none; }
.toc a.active {
  border-left-color: var(--accent);
  color: var(--accent);
  background: color-mix(in srgb, var(--accent) 8%, transparent);
}
.toc .nav-sub-item a { padding-left: 24px; font-size: 12.5px; }

.menu-toggle {
  display: none;
  position: fixed;
  top: 14px; right: 14px;
  z-index: 60;
  background: var(--bg-elevated);
  border: 1px solid var(--rule-strong);
  color: var(--text-primary);
  border-radius: 8px;
  padding: 8px 12px;
  font-family: var(--mono);
  font-size: 13px;
  cursor: pointer;
}

/* ---------- page layout ---------- */

.page {
  margin-left: var(--sidebar-w);
  padding: 0 48px 80px;
}

.content {
  max-width: var(--content-max);
  margin: 0 auto;
}

/* wide rows (interactives) escape the prose column, centered on it.
   .interactive.wide needs the extra specificity so .interactive's
   `margin: 36px 0` (declared later) can't cancel the margin-left. */
.wide,
.interactive.wide {
  width: min(var(--stage-max), calc(100vw - var(--sidebar-w) - 112px));
  margin-left: 50%;
  transform: translateX(-50%);
}

/* ---------- chapter header ---------- */

.lecture-header { padding: 64px 0 8px; }

.eyebrow {
  font-family: var(--mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--accent);
  margin-bottom: 14px;
}

.lecture-header h1 {
  font-family: var(--display);
  font-size: 42px;
  font-weight: 700;
  letter-spacing: -0.015em;
  line-height: 1.12;
  margin-bottom: 14px;
}

.lecture-desc {
  font-size: 18px;
  color: var(--text-secondary);
  max-width: 620px;
  margin-bottom: 18px;
}

.tags { display: flex; gap: 8px; flex-wrap: wrap; }
.tag {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  border: 1px solid var(--rule-strong);
  border-radius: 99px;
  padding: 3px 10px;
}

/* ---------- top + bottom nav ---------- */

.lecture-nav-top {
  display: flex;
  justify-content: space-between;
  font-family: var(--mono);
  font-size: 13px;
  padding: 18px 0;
  border-top: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  margin: 26px 0 8px;
}
.lecture-nav-top a { color: var(--text-secondary); }
.lecture-nav-top a:hover { color: var(--accent); text-decoration: none; }
.lecture-nav-top a:only-child { margin-left: auto; }

.lecture-nav {
  display: flex;
  gap: 16px;
  margin-top: 64px;
}
.lecture-nav > * { flex: 1; }
.nav-card {
  display: block;
  padding: 18px 20px;
  background: var(--bg-surface);
  border: 1px solid var(--rule);
  border-radius: 12px;
  transition: transform 0.15s ease, border-color 0.15s ease, box-shadow 0.15s ease;
}
.nav-card:hover {
  text-decoration: none;
  transform: translateY(-2px);
  border-color: var(--accent);
  box-shadow: 0 0 24px -8px var(--accent);
}
.nav-card .nav-dir {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  margin-bottom: 6px;
}
.nav-card .nav-title { color: var(--text-primary); font-weight: 600; font-size: 15px; }
.nav-card.next { text-align: right; }

/* ---------- article typography ---------- */

article { padding-top: 8px; }

.lecture-roadmap {
  font-size: 18px;
  color: var(--text-secondary);
  margin: 26px 0 10px;
}

article h2 {
  font-family: var(--display);
  font-size: 30px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 64px 0 16px;
  scroll-margin-top: 24px;
}

article h3 {
  font-family: var(--display);
  font-size: 22px;
  font-weight: 600;
  margin: 44px 0 12px;
  scroll-margin-top: 24px;
}

article h4 {
  font-size: 17px;
  font-weight: 600;
  margin: 30px 0 10px;
}

.section-number {
  font-family: var(--mono);
  font-size: 0.72em;
  font-weight: 500;
  color: var(--accent);
  opacity: 0.75;
  margin-right: 10px;
}

article p { margin: 14px 0; color: var(--text-secondary); }
article p strong, article li strong { color: var(--text-primary); }
article ul, article ol { margin: 14px 0 14px 26px; color: var(--text-secondary); }
article li { margin: 6px 0; }

article hr { border: none; border-top: 1px solid var(--rule); margin: 40px 0; }

article table {
  border-collapse: collapse;
  width: 100%;
  margin: 20px 0;
  font-size: 15px;
}
article th {
  font-family: var(--mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  text-align: left;
  padding: 8px 12px;
  border-bottom: 1px solid var(--rule-strong);
}
article td {
  padding: 8px 12px;
  border-bottom: 1px solid var(--rule);
  color: var(--text-secondary);
}

/* ---------- callouts ---------- */

.callout {
  margin: 24px 0;
  padding: 18px 22px;
  border-radius: 12px;
  border: 1px solid var(--rule);
  border-left: 3px solid var(--text-muted);
  background: var(--bg-surface);
}
.callout p { margin: 6px 0 0; }
.callout p:first-of-type { margin-top: 0; }

.callout-label {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  margin-bottom: 8px;
  color: var(--text-muted);
}

.callout.definition { border-left-color: var(--blue); background: color-mix(in srgb, var(--blue) 5%, var(--bg-surface)); }
.callout.definition .callout-label { color: var(--blue); }

.callout.model { border-left-color: var(--purple); background: color-mix(in srgb, var(--purple) 5%, var(--bg-surface)); }
.callout.model .callout-label { color: var(--purple); }

.callout.example { border-left-color: var(--amber); background: color-mix(in srgb, var(--amber) 5%, var(--bg-surface)); }
.callout.example .callout-label { color: var(--amber); }

.callout.insight { border-left-color: var(--green); background: color-mix(in srgb, var(--green) 5%, var(--bg-surface)); }
.callout.insight .callout-label { color: var(--green); }

.callout.note { opacity: 0.92; }

/* ---------- collapsible deep-dives ---------- */

details.collapsible {
  margin: 24px 0;
  border: 1px solid var(--rule);
  border-radius: 12px;
  background: var(--bg-surface);
}
details.collapsible summary {
  cursor: pointer;
  padding: 14px 20px;
  font-weight: 600;
  color: var(--text-primary);
  list-style: none;
}
details.collapsible summary::before {
  content: "+";
  font-family: var(--mono);
  color: var(--accent);
  margin-right: 10px;
}
details.collapsible[open] summary::before { content: "−"; }
.collapsible-content { padding: 0 20px 18px; }

/* ---------- interactive panels ---------- */

.interactive {
  margin: 36px 0;
  padding: 26px 28px 24px;
  background: var(--bg-surface);
  border: 1px solid var(--rule-strong);
  border-radius: 16px;
  box-shadow: 0 0 50px -24px rgba(45, 212, 237, 0.45),
              inset 0 1px 0 rgba(255, 255, 255, 0.03);
}

.interactive-label {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--accent);
  margin-bottom: 8px;
}
.interactive-label::before {
  content: "";
  display: inline-block;
  width: 7px; height: 7px;
  border-radius: 99px;
  background: var(--accent);
  box-shadow: 0 0 8px var(--accent);
  margin-right: 8px;
  vertical-align: 1px;
}

.interactive-title {
  font-family: var(--display);
  font-size: 19px;
  font-weight: 600;
  margin: 0 0 4px;
}

.interactive-hint {
  font-size: 14.5px;
  color: var(--text-muted);
  margin: 0 0 16px;
}

.interactive-stage {
  position: relative;
  width: 100%;
  display: flex;
  justify-content: center;
  margin: 8px 0 16px;
}
.interactive-stage canvas,
.interactive-stage svg {
  display: block;
  max-width: 100%;
  border-radius: 12px;
}

.interactive-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 14px 26px;
  align-items: center;
  padding-top: 14px;
  border-top: 1px solid var(--rule);
}

.control-group { display: flex; flex-direction: column; gap: 6px; min-width: 150px; }
.control-group.row { flex-direction: row; align-items: center; gap: 10px; }

.control-label {
  font-family: var(--mono);
  font-size: 11.5px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
}
.control-value { color: var(--text-primary); font-family: var(--mono); font-size: 13px; }

.interactive-readout {
  margin-top: 12px;
  font-family: var(--mono);
  font-size: 13.5px;
  color: var(--text-secondary);
  min-height: 1.4em;
}

/* sliders */
input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 200px;
  height: 4px;
  border-radius: 99px;
  background: var(--bg-hover);
  outline: none;
  cursor: pointer;
}
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px; height: 16px;
  border-radius: 99px;
  background: var(--accent);
  border: 2px solid var(--bg-deep);
  box-shadow: 0 0 10px var(--accent);
}
input[type="range"]::-moz-range-thumb {
  width: 14px; height: 14px;
  border-radius: 99px;
  background: var(--accent);
  border: 2px solid var(--bg-deep);
  box-shadow: 0 0 10px var(--accent);
}

/* buttons */
.btn {
  font-family: var(--mono);
  font-size: 13px;
  padding: 8px 16px;
  border-radius: 9px;
  border: 1px solid var(--rule-strong);
  background: var(--bg-elevated);
  color: var(--text-primary);
  cursor: pointer;
  transition: border-color 0.15s, box-shadow 0.15s, background 0.15s;
}
.btn:hover { border-color: var(--accent); }
.btn.primary {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 14%, var(--bg-elevated));
  box-shadow: 0 0 18px -6px var(--accent);
}
.btn:disabled { opacity: 0.4; cursor: default; }
.btn:disabled:hover { border-color: var(--rule-strong); }

/* segmented toggles */
.seg-toggle {
  display: inline-flex;
  border: 1px solid var(--rule-strong);
  border-radius: 10px;
  overflow: hidden;
}
.seg-btn {
  font-family: var(--mono);
  font-size: 12.5px;
  padding: 7px 14px;
  background: transparent;
  border: none;
  border-right: 1px solid var(--rule);
  color: var(--text-secondary);
  cursor: pointer;
}
.seg-btn:last-child { border-right: none; }
.seg-btn[aria-pressed="true"] {
  background: color-mix(in srgb, var(--accent) 16%, transparent);
  color: var(--accent);
}

/* ---------- boss panel ---------- */

.boss-panel {
  margin: 56px 0 8px;
  padding: 30px 32px;
  border-radius: 16px;
  border: 1px solid color-mix(in srgb, var(--rose) 45%, var(--rule-strong));
  background:
    radial-gradient(ellipse at top left,
      color-mix(in srgb, var(--rose) 8%, transparent), transparent 60%),
    var(--bg-surface);
}
.boss-panel .interactive-label { color: var(--rose); }
.boss-panel .interactive-label::before { background: var(--rose); box-shadow: 0 0 8px var(--rose); }

.quiz-options { display: grid; gap: 10px; margin: 16px 0; }
.quiz-option {
  text-align: left;
  padding: 12px 16px;
  border-radius: 10px;
  border: 1px solid var(--rule-strong);
  background: var(--bg-elevated);
  color: var(--text-primary);
  font-family: var(--sans);
  font-size: 15px;
  cursor: pointer;
  transition: border-color 0.12s;
}
.quiz-option:hover { border-color: var(--accent); }
.quiz-option.correct { border-color: var(--green); background: color-mix(in srgb, var(--green) 10%, var(--bg-elevated)); }
.quiz-option.wrong { border-color: var(--rose); background: color-mix(in srgb, var(--rose) 10%, var(--bg-elevated)); }

.boss-progress {
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--text-muted);
}

/* ---------- math ---------- */

.katex { font-size: 1.05em; }
.katex-display { margin: 22px 0; overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

[data-tip] {
  border-bottom: 1px dotted var(--accent);
  cursor: help;
}

.math-tooltip {
  position: absolute;
  max-width: 290px;
  padding: 10px 14px;
  background: var(--bg-elevated);
  border: 1px solid var(--rule-strong);
  border-radius: 10px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.55), 0 0 20px -10px var(--accent);
  font-family: var(--sans);
  font-size: 13.5px;
  line-height: 1.5;
  color: var(--text-secondary);
  z-index: 200;
  pointer-events: none;
}

/* ---------- hub (index) ---------- */

.hub-page { margin-left: 0; }

.hero {
  position: relative;
  min-height: 78vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  overflow: hidden;
}
.hero-cloud {
  position: absolute;
  inset: 0;
  z-index: 0;
}
.hero-inner {
  position: relative;
  z-index: 1;
  padding: 60px 24px;
  background: radial-gradient(ellipse 60% 50% at center,
    rgba(6, 9, 16, 0.78), rgba(6, 9, 16, 0.35) 55%, transparent 75%);
}

.hero h1 {
  font-family: var(--display);
  font-size: 56px;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.05;
  margin: 14px 0 18px;
  text-shadow: 0 0 60px rgba(45, 212, 237, 0.35);
}

.hero-sub {
  font-size: 19px;
  color: var(--text-secondary);
  max-width: 560px;
  margin: 0 auto;
}

.hero-prereq {
  margin-top: 26px;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--text-muted);
}

.hub-main { max-width: 980px; margin: 0 auto; padding: 24px 32px 100px; }

.chapter-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; margin-top: 28px; }

.chapter-card {
  position: relative;
  display: block;
  padding: 26px 26px 22px;
  background: var(--bg-surface);
  border: 1px solid var(--rule);
  border-radius: 16px;
  overflow: hidden;
  transition: transform 0.16s ease, border-color 0.16s ease, box-shadow 0.16s ease;
}
.chapter-card:hover {
  text-decoration: none;
  transform: translateY(-3px);
  border-color: var(--accent);
  box-shadow: 0 0 36px -12px var(--accent);
}
.chapter-num {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--accent);
  margin-bottom: 10px;
}
.chapter-card h3 {
  font-family: var(--display);
  font-size: 21px;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
}
.chapter-card p { font-size: 14.5px; color: var(--text-secondary); }
.chapter-card .tags { margin-top: 14px; }
.chapter-card.coming-soon { opacity: 0.55; pointer-events: none; }

.hub-section-label {
  font-family: var(--mono);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--text-muted);
  margin-top: 56px;
}

/* ---------- footer ---------- */

.site-footer {
  margin-top: 70px;
  padding-top: 24px;
  border-top: 1px solid var(--rule);
  font-family: var(--mono);
  font-size: 12.5px;
  color: var(--text-muted);
}

/* ---------- responsive ---------- */

@media (max-width: 960px) {
  .chapter-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
  .sidebar {
    transform: translateX(-100%);
    transition: transform 0.2s ease;
    width: min(300px, 84vw);
  }
  .sidebar.open { transform: translateX(0); box-shadow: 0 0 60px rgba(0,0,0,0.6); }
  .menu-toggle { display: block; }

  .page { margin-left: 0; padding: 0 20px 60px; }

  .lecture-header { padding-top: 48px; }
  .lecture-header h1 { font-size: 30px; }
  .hero h1 { font-size: 34px; }
  .hero-sub { font-size: 16px; }
  article h2 { font-size: 24px; }
  article h3 { font-size: 19px; }
  body { font-size: 16px; }

  .lecture-nav { flex-direction: column; }
  .nav-card.next { text-align: left; }
  .lecture-nav-top { font-size: 12px; }

  .interactive { padding: 18px 16px; margin-left: -4px; margin-right: -4px; }
  .interactive-controls { gap: 12px; }
  input[type="range"] { width: 150px; }
  .wide, .interactive.wide { width: 100%; margin-left: 0; transform: none; }
}