@import url('https://fonts.googleapis.com/css2?family=Newsreader:ital,opsz,wght@0,6..72,400;0,6..72,500;0,6..72,600;1,6..72,400&family=JetBrains+Mono:wght@400;500;600&family=Inter:wght@400;500;600&display=swap');

:root {
  --bg: #0b0e11;
  --bg-raised: #12161b;
  --bg-inset: #080a0c;
  --ink: #e8e6e1;
  --ink-dim: #b8b5ad;
  --ink-faint: #6b7280;
  --line: #23282f;
  --line-bright: #343b44;
  --amber: #ffb020;
  --amber-dim: #7a5a1c;
  --cyan: #3fc1c9;
  --cyan-dim: #1f5c60;
  --danger: #e05252;

  --serif: 'Newsreader', Georgia, serif;
  --mono: 'JetBrains Mono', 'SF Mono', Consolas, monospace;
  --sans: 'Inter', -apple-system, sans-serif;

  --sidebar-w: 280px;
  --content-max: 860px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

::selection { background: var(--amber-dim); color: var(--ink); }

a { color: var(--cyan); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- background instrument grid ---------- */
.grid-bg {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(255,255,255,0.025) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255,255,255,0.025) 1px, transparent 1px);
  background-size: 32px 32px;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, black 30%, transparent 75%);
}

/* ---------- layout shell ---------- */
.shell {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  min-height: 100vh;
}

@media (max-width: 900px) {
  .shell { grid-template-columns: 1fr; }
  .sidebar { position: static; height: auto; }
}

/* ---------- sidebar ---------- */
.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  border-right: 1px solid var(--line);
  padding: 28px 22px 40px;
  background: linear-gradient(180deg, var(--bg-raised), var(--bg));
}

.sidebar::-webkit-scrollbar { width: 6px; }
.sidebar::-webkit-scrollbar-thumb { background: var(--line-bright); border-radius: 3px; }

.brand {
  display: block;
  margin-bottom: 4px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--amber);
  text-transform: uppercase;
}
.brand-sub {
  display: block;
  margin-bottom: 28px;
  font-family: var(--serif);
  font-size: 20px;
  color: var(--ink);
  line-height: 1.3;
}

.nav-group { margin-bottom: 4px; }
.nav-group-title {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-faint);
  padding: 14px 10px 6px;
}
.nav-link {
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 7px 10px;
  border-radius: 5px;
  font-size: 13.5px;
  color: var(--ink-dim);
  border-left: 2px solid transparent;
}
.nav-link:hover { background: rgba(255,255,255,0.04); color: var(--ink); text-decoration: none; }
.nav-link.active {
  color: var(--amber);
  background: rgba(255,176,32,0.07);
  border-left-color: var(--amber);
}
.nav-num { font-family: var(--mono); font-size: 11px; color: var(--ink-faint); min-width: 22px; }
.nav-link.active .nav-num { color: var(--amber-dim); }

.sidebar-footer {
  margin-top: 28px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--ink-faint);
  line-height: 1.6;
}

/* ---------- main content ---------- */
.main {
  position: relative;
  z-index: 1;
  padding: 56px 48px 120px;
}
@media (max-width: 900px) { .main { padding: 40px 20px 100px; } }

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

.chapter-eyebrow {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--cyan);
  margin-bottom: 10px;
}

h1.chapter-title {
  font-family: var(--serif);
  font-weight: 500;
  font-size: clamp(32px, 5vw, 48px);
  line-height: 1.08;
  margin: 0 0 18px;
  color: var(--ink);
}

.chapter-dek {
  font-family: var(--serif);
  font-style: italic;
  font-size: 19px;
  color: var(--ink-dim);
  max-width: 640px;
  margin: 0 0 44px;
  line-height: 1.5;
}

.content h2 {
  font-family: var(--serif);
  font-weight: 500;
  font-size: 27px;
  color: var(--ink);
  margin: 64px 0 18px;
  padding-top: 8px;
  border-top: 1px solid var(--line);
  display: flex;
  align-items: baseline;
  gap: 12px;
}
.content h2 .sec-num {
  font-family: var(--mono);
  font-size: 14px;
  color: var(--amber);
  font-weight: 400;
}

.content h3 {
  font-family: var(--sans);
  font-weight: 600;
  font-size: 17px;
  color: var(--ink);
  margin: 34px 0 12px;
  letter-spacing: -0.01em;
}

.content p { color: var(--ink-dim); margin: 0 0 16px; font-size: 15.5px; }
.content p strong { color: var(--ink); font-weight: 600; }
.content ul, .content ol { color: var(--ink-dim); font-size: 15.5px; padding-left: 22px; margin: 0 0 16px; }
.content li { margin-bottom: 6px; }
.content li::marker { color: var(--amber-dim); }

code {
  font-family: var(--mono);
  font-size: 0.88em;
  background: var(--bg-inset);
  border: 1px solid var(--line);
  padding: 1px 6px;
  border-radius: 4px;
  color: var(--cyan);
}

.eq {
  font-family: var(--mono);
  font-size: 15px;
  color: var(--ink);
  background: var(--bg-inset);
  border: 1px solid var(--line);
  border-left: 3px solid var(--cyan-dim);
  padding: 16px 20px;
  border-radius: 6px;
  margin: 20px 0;
  overflow-x: auto;
}
.eq .var { color: var(--cyan); font-style: italic; }

/* ---------- callouts ---------- */
.callout {
  border: 1px solid var(--line);
  border-left: 3px solid var(--amber-dim);
  background: var(--bg-raised);
  border-radius: 6px;
  padding: 16px 20px;
  margin: 24px 0;
}
.callout-label {
  font-family: var(--mono);
  font-size: 10.5px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--amber);
  margin-bottom: 6px;
}
.callout p:last-child { margin-bottom: 0; }

.callout.mission { border-left-color: var(--cyan-dim); }
.callout.mission .callout-label { color: var(--cyan); }

.callout.intuition { border-left-color: #6ba85a; background: rgba(107,168,90,0.06); }
.callout.intuition .callout-label { color: #8fd177; }

.callout.example { border-left-color: var(--amber-dim); background: rgba(255,176,32,0.05); }
.callout.example .callout-label { color: var(--amber); }

/* ---------- plain-language "in short" strip ---------- */
.tldr {
  display: flex;
  gap: 14px;
  align-items: flex-start;
  background: linear-gradient(135deg, rgba(63,193,201,0.08), rgba(255,176,32,0.05));
  border: 1px solid var(--line-bright);
  border-radius: 8px;
  padding: 14px 18px;
  margin: 18px 0 28px;
}
.tldr .tldr-icon {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--bg);
  background: var(--amber);
  border-radius: 4px;
  padding: 3px 7px;
  font-weight: 600;
  letter-spacing: 0.04em;
  white-space: nowrap;
}
.tldr p { margin: 0; color: var(--ink); font-size: 14.5px; }

/* ---------- panels for interactive demos ---------- */
.panel {
  border: 1px solid var(--line);
  background: var(--bg-raised);
  border-radius: 10px;
  padding: 24px;
  margin: 28px 0 36px;
}
.panel-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 4px;
  flex-wrap: wrap;
  gap: 8px;
}
.panel-title {
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--cyan);
}
.panel-hint {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--ink-faint);
}
.panel-body { margin-top: 16px; }

.controls-row {
  display: flex;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
  margin-top: 14px;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-dim);
}
.controls-row label { display: flex; align-items: center; gap: 8px; }
.controls-row input[type="range"] {
  accent-color: var(--amber);
  width: 140px;
}
.controls-row select, .controls-row button {
  font-family: var(--mono);
  font-size: 12px;
  background: var(--bg-inset);
  color: var(--ink);
  border: 1px solid var(--line-bright);
  border-radius: 5px;
  padding: 6px 10px;
  cursor: pointer;
}
.controls-row button:hover, .controls-row select:hover { border-color: var(--amber-dim); }
.controls-row button.active { border-color: var(--amber); color: var(--amber); }

.readout {
  font-family: var(--mono);
  font-size: 11.5px;
  color: var(--ink-faint);
  margin-top: 10px;
  border-top: 1px dashed var(--line);
  padding-top: 10px;
}
.readout .val { color: var(--amber); }

canvas { display: block; max-width: 100%; border-radius: 6px; }

/* ---------- probe cursor motif ---------- */
.probe-surface { position: relative; cursor: crosshair; }
.probe-tag {
  position: absolute;
  pointer-events: none;
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--amber);
  background: rgba(8,10,12,0.9);
  border: 1px solid var(--amber-dim);
  padding: 3px 7px;
  border-radius: 4px;
  transform: translate(12px, -50%);
  white-space: nowrap;
  z-index: 5;
  opacity: 0;
  transition: opacity 0.1s;
}

/* ---------- comparison grid ---------- */
.compare-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
  margin: 24px 0;
}
.compare-cell {
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
  background: var(--bg-inset);
}
.compare-cell canvas { width: 100%; }
.compare-cell-label {
  font-family: var(--mono);
  font-size: 10.5px;
  color: var(--ink-faint);
  padding: 8px 10px;
  border-top: 1px solid var(--line);
}

/* ---------- table ---------- */
table { width: 100%; border-collapse: collapse; margin: 20px 0; font-size: 14px; }
th, td { text-align: left; padding: 10px 14px; border-bottom: 1px solid var(--line); color: var(--ink-dim); }
th { font-family: var(--mono); font-size: 11px; letter-spacing: 0.06em; text-transform: uppercase; color: var(--ink-faint); font-weight: 500; }
td:first-child, th:first-child { color: var(--ink); }

/* ---------- chapter nav footer ---------- */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  margin-top: 80px;
  padding-top: 24px;
  border-top: 1px solid var(--line);
}
.chapter-nav a {
  flex: 1;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px 18px;
  color: var(--ink-dim);
  text-decoration: none;
  transition: border-color 0.15s;
}
.chapter-nav a:hover { border-color: var(--amber-dim); }
.chapter-nav .dir { font-family: var(--mono); font-size: 10px; color: var(--ink-faint); text-transform: uppercase; letter-spacing: 0.08em; }
.chapter-nav .ttl { font-family: var(--serif); font-size: 16px; color: var(--ink); margin-top: 4px; }
.chapter-nav .next { text-align: right; }

/* ---------- badges ---------- */
.badge {
  display: inline-block;
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 2px 8px;
  border-radius: 4px;
  border: 1px solid var(--amber-dim);
  color: var(--amber);
  margin-left: 8px;
  vertical-align: middle;
}

/* ---------- home hero ---------- */
.hero {
  min-height: 78vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
}
.hero-eyebrow {
  font-family: var(--mono);
  font-size: 12.5px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
  margin-bottom: 20px;
}
.hero h1 {
  font-family: var(--serif);
  font-weight: 500;
  font-size: clamp(40px, 6.4vw, 72px);
  line-height: 1.04;
  margin: 0 0 24px;
  max-width: 900px;
}
.hero h1 em { color: var(--amber); font-style: normal; }
.hero p.lead {
  font-size: 18px;
  color: var(--ink-dim);
  max-width: 620px;
  line-height: 1.6;
  margin-bottom: 36px;
}
.hero-cta { display: flex; gap: 14px; flex-wrap: wrap; }
.btn {
  font-family: var(--mono);
  font-size: 13px;
  padding: 12px 22px;
  border-radius: 7px;
  border: 1px solid var(--line-bright);
  color: var(--ink);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
.btn:hover { text-decoration: none; border-color: var(--amber); color: var(--amber); }
.btn.primary { background: var(--amber); color: #0b0e11; border-color: var(--amber); font-weight: 600; }
.btn.primary:hover { background: #ffc450; color: #0b0e11; }

.track-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 18px;
  margin-top: 60px;
}
.track-card {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 22px;
  background: var(--bg-raised);
  transition: border-color 0.15s, transform 0.15s;
}
.track-card:hover { border-color: var(--amber-dim); transform: translateY(-2px); text-decoration: none; }
.track-card .tk-num { font-family: var(--mono); font-size: 11px; color: var(--ink-faint); }
.track-card h3 { font-family: var(--serif); font-size: 19px; color: var(--ink); margin: 8px 0 8px; font-weight: 500; }
.track-card p { font-size: 13.5px; color: var(--ink-faint); margin: 0; }