:root {
  --bg: #f3efe6;
  --paper: #fffdf8;
  --ink: #1c1915;
  --muted: #5e584e;
  --line: #e0d6c8;
  --accent: #0f6e6b;
  --accent-dark: #0a4c4a;
  --canvas: #172033;
  --nav-offset: 4.25rem;
  color-scheme: light;
}

* { box-sizing: border-box; }

[hidden] { display: none !important; }

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: "Avenir Next", "Segoe UI", Helvetica, Arial, sans-serif;
  font-size: 1.05rem;
  line-height: 1.55;
}

.site-header,
.lecture-section,
.site-footer {
  width: min(1120px, calc(100% - 2rem));
  margin-inline: auto;
}

.site-header {
  padding: 2.5rem 0 1.5rem;
}

.eyebrow {
  margin: 0 0 0.4rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.78rem;
  color: var(--accent-dark);
  font-weight: 600;
}

h1, h2, h3 {
  font-family: Palatino, "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  font-weight: 600;
  line-height: 1.2;
}

h1 {
  margin: 0 0 0.75rem;
  font-size: clamp(2rem, 4vw, 3.1rem);
}

.lede {
  margin: 0;
  max-width: 42rem;
  font-size: 1.2rem;
  color: var(--muted);
}

.section-nav {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  gap: 0.35rem;
  overflow-x: auto;
  padding: 0.55rem 1rem;
  background: rgba(243, 239, 230, 0.94);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}

.section-nav a {
  flex: 0 0 auto;
  color: var(--muted);
  text-decoration: none;
  font-size: 0.86rem;
  padding: 0.35rem 0.7rem;
  border-radius: 999px;
}

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

.section-nav a.is-current {
  background: var(--ink);
  color: var(--bg);
}

.lecture-section {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(300px, 0.95fr);
  gap: 2.25rem;
  align-items: start;
  padding: 2.75rem 0;
  border-top: 1px solid var(--line);
  scroll-margin-top: var(--nav-offset);
}

.kicker {
  margin: 0 0 0.25rem;
  color: var(--accent-dark);
  font-weight: 700;
  letter-spacing: 0.06em;
}

h2 {
  margin: 0 0 0.8rem;
  font-size: clamp(1.6rem, 2.5vw, 2.1rem);
}

h3 {
  margin: 1.25rem 0 0.4rem;
  font-size: 1.15rem;
}

.prose p { margin: 0.7rem 0; }

.prose ul, .prose ol { margin: 0.4rem 0 0.8rem; padding-left: 1.2rem; }

.prose li + li { margin-top: 0.25rem; }

blockquote {
  margin: 1rem 0;
  padding: 0.2rem 0 0.2rem 1rem;
  border-left: 3px solid var(--accent);
  font-family: Palatino, "Iowan Old Style", Georgia, serif;
  font-size: 1.25rem;
  line-height: 1.35;
}

.chip-list, .word-list, .progression {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  list-style: none;
  padding: 0;
  margin: 0.6rem 0 1rem;
}

.chip-list li, .word-list li, .progression li {
  margin: 0;
  padding: 0.25rem 0.65rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--paper);
  font-size: 0.92rem;
}

.progression li.is-here {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
}

.split-notes {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.8rem;
  margin: 0.8rem 0 1rem;
}

.split-notes div {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 0.8rem 1rem;
}

.split-notes h3 { margin-top: 0; }

.question-list { padding-left: 1.2rem; }

.question-list li { margin: 0.55rem 0; }

.demo { position: sticky; top: var(--nav-offset); }

.demo-frame {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 12px 32px rgba(28, 25, 21, 0.06);
}

.demo-controls, .slider-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  align-items: center;
  padding: 0.75rem;
}

.slider-row { padding-top: 0; }

.slider-row label { font-size: 0.92rem; }

.slider-row input[type="range"] { flex: 1; min-width: 8rem; }

button {
  font: inherit;
  font-size: 0.9rem;
  color: var(--ink);
  background: white;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.38rem 0.75rem;
  cursor: pointer;
}

button:hover { border-color: var(--accent); }

button[aria-pressed="true"] {
  background: var(--accent);
  border-color: var(--accent);
  color: white;
}

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

.code-panel {
  margin: 0 0.75rem 0.75rem;
  background: var(--canvas);
  color: #d7deea;
  border-radius: 10px;
  padding: 0.7rem 0.8rem;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.82rem;
  line-height: 1.45;
}

.code-lines {
  list-style: none;
  margin: 0;
  padding: 0;
}

.code-lines li {
  padding: 0.08rem 0.35rem;
  border-radius: 4px;
}

.code-lines li.indent { padding-left: 1.3rem; }

.code-lines li.is-active {
  background: rgba(226, 160, 74, 0.28);
  color: #fff8ea;
}

.observe-note {
  margin: 0;
  color: #d7deea;
}

.sketch-host {
  width: 100%;
  background: var(--canvas);
  line-height: 0;
}

.sketch-host canvas {
  display: block;
  width: 100% !important;
  height: auto !important;
}

.demo-status, .demo-summary {
  margin: 0;
  padding: 0.8rem 1rem;
}

.demo-status {
  min-height: 3.2rem;
  font-size: 0.98rem;
}

.demo-summary {
  color: var(--muted);
  font-size: 0.92rem;
  border-top: 1px solid var(--line);
}

.loop-row {
  margin: 0.75rem 1rem 0.25rem;
}

.deliverables {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.deliverables article {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 0.85rem 1rem;
}

.deliverables h3 {
  margin: 0 0 0.2rem;
  font-size: 1.05rem;
}

.deliverables p {
  margin: 0;
  color: var(--muted);
}

.site-footer {
  padding: 1rem 0 2.5rem;
  color: var(--muted);
  border-top: 1px solid var(--line);
}

@media (max-width: 860px) {
  .lecture-section {
    grid-template-columns: minmax(0, 1fr);
    gap: 1.25rem;
  }

  .demo { position: static; }

  .split-notes { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}