/* =========================================================================
   JEPA & World Models — an interactive essay
   Distill-pub-style design, byhand.ai-flavored touches.
   ========================================================================= */

:root {
  --ink: #1a1a1a;
  --ink-soft: #555;
  --ink-faint: #888;
  --bg: #ffffff;
  --bg-soft: #fafafa;
  --bg-card: #f5f3ef;
  --rule: #e6e6e6;
  --rule-soft: #f0f0f0;
  --accent: #ff6b35;
  --accent-soft: #ffe5d8;
  --secondary: #2c5aa0;
  --secondary-soft: #d8e3f3;
  --good: #2a9d4a;
  --warn: #e0a800;
  --bad: #c0392b;
  /* Topic color coding — kept consistent across all diagrams */
  --color-context: #2c5aa0;
  --color-target: #ff6b35;
  --color-predictor: #2a9d4a;
  --color-encoder: #6c5ce7;
  --color-latent: #d3406e;

  --body-font: "Source Serif Pro", "Source Serif", "Iowan Old Style", "Apple Garamond", Baskerville, "Times New Roman", serif;
  --ui-font: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --mono-font: "JetBrains Mono", "SF Mono", Menlo, Consolas, monospace;

  --body-max: 720px;
  --wide-max: 1080px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--body-font);
  font-size: 18px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-feature-settings: "kern", "liga", "calt";
}

/* ---------- Layout ------------------------------------------------------- */
.page {
  display: grid;
  grid-template-columns: 220px minmax(0, 1fr);
  gap: 32px;
  max-width: 1400px;
  margin: 0 auto;
  padding: 24px 32px 96px 32px;
}

.toc {
  position: sticky;
  top: 24px;
  align-self: start;
  font-family: var(--ui-font);
  font-size: 13px;
  border-right: 1px solid var(--rule);
  padding-right: 16px;
  max-height: calc(100vh - 48px);
  overflow-y: auto;
}

.toc .toc-title {
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-faint);
  margin: 8px 0 12px 0;
  font-size: 11px;
}

.toc ol {
  list-style: none;
  padding: 0;
  margin: 0;
  counter-reset: section;
}

.toc li {
  counter-increment: section;
  margin: 4px 0;
}

.toc a {
  text-decoration: none;
  color: var(--ink-soft);
  display: block;
  padding: 4px 6px;
  border-radius: 3px;
  border-left: 2px solid transparent;
  transition: all 0.15s;
}

.toc a::before {
  content: counter(section, decimal-leading-zero) "  ";
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
}

.toc a:hover { color: var(--ink); background: var(--bg-soft); }
.toc a.active { color: var(--accent); border-left-color: var(--accent); background: var(--accent-soft); }

main { min-width: 0; }

/* ---------- Typography for the article body ------------------------------ */
.body {
  max-width: var(--body-max);
  margin: 0 auto;
}

.wide {
  max-width: var(--wide-max);
  margin: 24px auto;
}

h1, h2, h3, h4 { font-family: var(--ui-font); font-weight: 700; line-height: 1.2; }
h1 { font-size: 56px; letter-spacing: -0.02em; margin: 12px 0 8px 0; }
h2 { font-size: 32px; letter-spacing: -0.01em; margin: 64px 0 12px 0; }
h3 { font-size: 22px; margin: 36px 0 8px 0; }
h4 { font-size: 16px; text-transform: uppercase; letter-spacing: 0.07em; color: var(--ink-soft); margin: 24px 0 8px 0; }

p { margin: 0 0 18px 0; }
p + p { text-indent: 0; }

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

code, kbd { font-family: var(--mono-font); font-size: 0.88em; background: var(--bg-soft); padding: 1px 5px; border-radius: 3px; }

blockquote {
  border-left: 3px solid var(--accent);
  margin: 24px 0;
  padding: 4px 18px;
  color: var(--ink-soft);
  font-style: italic;
  background: var(--bg-soft);
}

hr { border: none; border-top: 1px solid var(--rule); margin: 48px 0; }

.section-eyebrow {
  font-family: var(--ui-font);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--accent);
  font-weight: 600;
  margin-top: 24px;
}

/* ---------- Sidenotes ---------------------------------------------------- */
.sidenote {
  font-family: var(--ui-font);
  font-size: 13px;
  line-height: 1.4;
  color: var(--ink-soft);
  float: right;
  clear: right;
  margin: 4px -210px 16px 0;
  width: 190px;
  border-left: 1px solid var(--rule);
  padding: 0 0 0 12px;
}

@media (max-width: 1180px) {
  .sidenote {
    float: none;
    display: block;
    margin: 12px 0;
    background: var(--bg-soft);
    border-left: 2px solid var(--accent);
    padding: 8px 12px;
    width: auto;
  }
}

/* ---------- Glossary popovers ------------------------------------------- */
.gloss {
  border-bottom: 1px dotted var(--secondary);
  cursor: help;
  position: relative;
  color: inherit;
}
.gloss:hover { border-bottom-color: var(--accent); color: var(--accent); }

.gloss-popover {
  position: absolute;
  z-index: 1000;
  background: #fff;
  border: 1px solid var(--ink);
  box-shadow: 0 6px 24px rgba(0,0,0,0.18);
  padding: 12px 14px;
  font-family: var(--ui-font);
  font-size: 13.5px;
  line-height: 1.45;
  color: var(--ink);
  max-width: 320px;
  border-radius: 4px;
}
.gloss-popover .term {
  font-weight: 700;
  color: var(--accent);
  display: block;
  margin-bottom: 4px;
  font-size: 12px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

/* ---------- Captions & figures ------------------------------------------ */
figure { margin: 24px 0; }
figcaption {
  font-family: var(--ui-font);
  font-size: 13px;
  color: var(--ink-soft);
  margin-top: 8px;
  line-height: 1.45;
}
figcaption .label { color: var(--accent); font-weight: 700; margin-right: 6px; }

/* ---------- Interactive widget shell ------------------------------------ */
.widget {
  border: 1px solid var(--rule);
  border-radius: 8px;
  background: var(--bg);
  margin: 24px 0;
  overflow: hidden;
  box-shadow: 0 1px 0 rgba(0,0,0,0.02);
}
.widget-header {
  padding: 10px 16px;
  border-bottom: 1px solid var(--rule);
  background: var(--bg-soft);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--ui-font);
  font-size: 12px;
  color: var(--ink-soft);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.widget-header .badge {
  background: var(--accent);
  color: #fff;
  font-size: 10px;
  padding: 2px 8px;
  border-radius: 10px;
  letter-spacing: 0.05em;
}
.widget-body { padding: 16px; }
.widget-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 14px 22px;
  align-items: center;
  font-family: var(--ui-font);
  font-size: 13px;
  padding: 12px 16px;
  border-top: 1px solid var(--rule);
  background: var(--bg-soft);
}
.widget-controls .ctrl {
  display: flex;
  flex-direction: column;
  gap: 4px;
}
.widget-controls .ctrl-row {
  display: flex;
  gap: 8px;
  align-items: center;
}
.widget-controls label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-faint);
  font-weight: 600;
}
.widget-controls input[type="range"] {
  width: 140px;
  accent-color: var(--accent);
}
.widget-controls .value {
  font-variant-numeric: tabular-nums;
  color: var(--ink);
  font-weight: 600;
  min-width: 32px;
  display: inline-block;
  text-align: right;
}
.widget-controls button, .btn {
  font-family: var(--ui-font);
  font-size: 12px;
  font-weight: 600;
  padding: 6px 12px;
  border: 1px solid var(--ink);
  background: var(--bg);
  color: var(--ink);
  border-radius: 4px;
  cursor: pointer;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  transition: all 0.12s;
}
.widget-controls button:hover, .btn:hover { background: var(--ink); color: #fff; }
.widget-controls button.primary, .btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.widget-controls button.primary:hover, .btn.primary:hover { background: var(--ink); border-color: var(--ink); }
.widget-controls button.ghost { border-color: var(--rule); color: var(--ink-soft); }
.widget-controls button[aria-pressed="true"] { background: var(--secondary); color: #fff; border-color: var(--secondary); }

.toggle-row {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.metric {
  display: inline-flex;
  flex-direction: column;
  font-family: var(--ui-font);
  font-size: 11px;
  color: var(--ink-faint);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.metric .v {
  font-size: 18px;
  font-weight: 700;
  color: var(--ink);
  text-transform: none;
  letter-spacing: 0;
  font-variant-numeric: tabular-nums;
}

/* ---------- Hero --------------------------------------------------------- */
#hero {
  padding: 48px 0 32px 0;
  border-bottom: 1px solid var(--rule);
}
#hero .eyebrow {
  font-family: var(--ui-font);
  font-size: 13px;
  letter-spacing: 0.12em;
  color: var(--accent);
  text-transform: uppercase;
  font-weight: 700;
}
#hero h1 {
  font-size: 64px;
  line-height: 1.05;
  margin-top: 8px;
  font-family: var(--body-font);
  font-weight: 700;
  letter-spacing: -0.02em;
}
#hero .lede {
  font-size: 22px;
  line-height: 1.45;
  color: var(--ink-soft);
  max-width: 660px;
  margin-top: 20px;
}
#hero .byline {
  font-family: var(--ui-font);
  font-size: 13px;
  color: var(--ink-faint);
  margin-top: 16px;
}

.hero-figure {
  margin: 36px auto 8px;
  max-width: 100%;
}

/* ---------- Tables ------------------------------------------------------- */
table {
  border-collapse: collapse;
  font-family: var(--ui-font);
  font-size: 13.5px;
  width: 100%;
  margin: 16px 0;
}
th, td { padding: 8px 12px; text-align: left; border-bottom: 1px solid var(--rule); }
th { background: var(--bg-soft); font-weight: 700; color: var(--ink); text-transform: uppercase; font-size: 11px; letter-spacing: 0.06em; }
tbody tr:hover { background: var(--bg-soft); }
tbody tr.highlight { background: var(--accent-soft); }

/* ---------- KaTeX shrink ------------------------------------------------- */
.katex { font-size: 1.05em !important; }
.katex-display { margin: 18px 0 !important; overflow-x: auto; overflow-y: hidden; }

/* ---------- SVG defaults ------------------------------------------------- */
svg { display: block; }
.diagram text { font-family: var(--ui-font); font-size: 12px; fill: var(--ink); }
.diagram .label-soft { fill: var(--ink-soft); font-size: 11px; }
.diagram .arrow-head { fill: var(--ink); }
.diagram .box {
  fill: var(--bg-soft);
  stroke: var(--ink);
  stroke-width: 1.5;
}
.diagram .box.context { fill: var(--secondary-soft); stroke: var(--color-context); }
.diagram .box.target  { fill: var(--accent-soft); stroke: var(--color-target); }
.diagram .box.predictor { fill: #e0f5e6; stroke: var(--color-predictor); }
.diagram .box.encoder { fill: #ece6ff; stroke: var(--color-encoder); }

.pulse { animation: pulse 1.2s ease-in-out infinite; }
@keyframes pulse {
  0%, 100% { stroke-width: 1.5; }
  50% { stroke-width: 3.5; }
}

/* ---------- Tooltip ------------------------------------------------------ */
.tooltip {
  position: absolute;
  pointer-events: none;
  background: var(--ink);
  color: #fff;
  padding: 6px 10px;
  border-radius: 4px;
  font-family: var(--ui-font);
  font-size: 12px;
  line-height: 1.35;
  max-width: 260px;
  z-index: 200;
  opacity: 0;
  transition: opacity 0.12s;
  pointer-events: none;
}
.tooltip.show { opacity: 1; }

/* ---------- Color key chip ----------------------------------------------- */
.color-key {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-family: var(--ui-font);
  font-size: 12px;
  margin-right: 14px;
  color: var(--ink-soft);
}
.color-key::before {
  content: "";
  width: 12px; height: 12px;
  border-radius: 2px;
  background: var(--accent);
}
.color-key.context::before { background: var(--color-context); }
.color-key.target::before { background: var(--color-target); }
.color-key.predictor::before { background: var(--color-predictor); }
.color-key.encoder::before { background: var(--color-encoder); }
.color-key.latent::before { background: var(--color-latent); }

/* ---------- Method cards (SSL landscape) -------------------------------- */
.method-node circle { stroke: var(--ink); stroke-width: 1.5; fill: #fff; cursor: grab; }
.method-node.dragging circle { stroke-width: 3; }
.method-node text { font-size: 11px; font-family: var(--ui-font); pointer-events: none; fill: var(--ink); }
.method-info {
  position: absolute;
  background: #fff;
  border: 1px solid var(--ink);
  border-radius: 4px;
  padding: 8px 12px;
  font-family: var(--ui-font);
  font-size: 12.5px;
  max-width: 280px;
  box-shadow: 0 4px 16px rgba(0,0,0,0.12);
}

/* ---------- Timeline ----------------------------------------------------- */
.tl-row {
  display: grid;
  grid-template-columns: 70px 1fr;
  gap: 16px;
  align-items: start;
  margin: 12px 0;
}
.tl-year {
  font-family: var(--ui-font);
  font-weight: 700;
  font-size: 16px;
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
}
.tl-card {
  border: 1px solid var(--rule);
  padding: 12px 14px;
  border-radius: 6px;
  background: var(--bg-soft);
  font-size: 14.5px;
}
.tl-card .tl-title { font-weight: 700; font-family: var(--ui-font); }
.tl-card .tl-kind {
  display: inline-block;
  font-family: var(--ui-font);
  font-size: 10px;
  letter-spacing: 0.06em;
  padding: 2px 8px;
  border-radius: 10px;
  margin-left: 8px;
  text-transform: uppercase;
  vertical-align: middle;
}
.tl-kind.jepa { background: var(--accent-soft); color: var(--accent); }
.tl-kind.dreamer { background: #e0f5e6; color: var(--good); }
.tl-kind.generative { background: var(--secondary-soft); color: var(--secondary); }
.tl-kind.classic { background: #f0e6e0; color: #8c5a3d; }
.tl-kind.ssl { background: #ece6ff; color: var(--color-encoder); }
.tl-kind.robot { background: #ffe5d8; color: #b8541d; }
.tl-kind.spatial { background: #fff4cc; color: #8a6d00; }

/* ---------- Paradigm cards ---------------------------------------------- */
.paradigm-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 14px;
}
.paradigm-card {
  border: 1.5px solid var(--rule);
  padding: 14px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s;
  background: var(--bg-soft);
  font-size: 14px;
}
.paradigm-card:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(0,0,0,0.08); }
.paradigm-card.selected.jepa     { border-color: var(--color-target); background: var(--accent-soft); }
.paradigm-card.selected.pixel    { border-color: var(--secondary); background: var(--secondary-soft); }
.paradigm-card.selected.dreamer  { border-color: var(--good); background: #e0f5e6; }
.paradigm-card h4 { margin: 0 0 6px 0; font-size: 14px; }
.paradigm-card p { margin: 0; font-size: 13px; color: var(--ink-soft); }

/* ---------- Open problem wheel ------------------------------------------ */
.wheel-stage {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 24px;
  align-items: start;
}
.wheel-detail {
  padding: 14px 16px;
  border: 1px solid var(--rule);
  border-radius: 6px;
  background: var(--bg-soft);
  font-size: 15px;
  min-height: 240px;
}
.wheel-detail h4 { margin-top: 4px; font-size: 16px; color: var(--accent); }
.wheel-detail .why { color: var(--ink-soft); font-size: 13.5px; margin-top: 8px; }

/* ---------- Teaching ladder --------------------------------------------- */
.ladder-stage {
  border: 1px solid var(--rule);
  border-radius: 8px;
  padding: 18px 20px;
  background: var(--bg-soft);
  min-height: 150px;
  font-size: 16px;
  line-height: 1.55;
  position: relative;
}
.ladder-stage .level {
  display: inline-block;
  font-family: var(--ui-font);
  font-size: 11px;
  padding: 2px 10px;
  border-radius: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 12px;
  font-weight: 700;
}
.ladder-stage[data-level="0"] .level { background: var(--accent-soft); color: var(--accent); }
.ladder-stage[data-level="1"] .level { background: #ffe9c4; color: #8a6d00; }
.ladder-stage[data-level="2"] .level { background: var(--secondary-soft); color: var(--secondary); }
.ladder-stage[data-level="3"] .level { background: #ece6ff; color: var(--color-encoder); }
.ladder-stage[data-level="4"] .level { background: #e0f5e6; color: var(--good); }

/* ---------- Hand-drawn / rough utility class ---------------------------- */
.rough svg .rough-stroke { stroke-linecap: round; stroke-linejoin: round; }

/* ---------- Footer ------------------------------------------------------- */
.refs {
  border-top: 1px solid var(--rule);
  margin-top: 96px;
  padding-top: 32px;
  font-family: var(--ui-font);
  font-size: 13.5px;
}
.refs h2 { font-family: var(--body-font); font-weight: 700; }
.refs ol { padding-left: 24px; }
.refs li { margin: 8px 0; line-height: 1.5; color: var(--ink-soft); }
.refs li b { color: var(--ink); }

footer.site-foot {
  margin-top: 32px;
  font-family: var(--ui-font);
  font-size: 12px;
  color: var(--ink-faint);
  border-top: 1px solid var(--rule);
  padding-top: 16px;
  text-align: center;
}

/* ---------- JEPA widget responsive layout ------------------------------- */
.jepa-grid {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  gap: 24px;
  align-items: flex-start;
}
@media (max-width: 760px) {
  .jepa-grid { grid-template-columns: 1fr; }
  .jepa-left { max-width: 320px; margin: 0 auto; }
}

/* ---------- Mobile ------------------------------------------------------- */
@media (max-width: 900px) {
  .page { grid-template-columns: 1fr; padding: 16px; }
  .toc { display: none; }
  h1 { font-size: 40px; }
  #hero h1 { font-size: 44px; }
  #hero .lede { font-size: 18px; }
  .paradigm-grid { grid-template-columns: 1fr; }
  .wheel-stage { grid-template-columns: 1fr; }
}

/* ---------- Misc helpers ------------------------------------------------- */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.reveal.in { opacity: 1; transform: none; }

.row { display: flex; gap: 14px; flex-wrap: wrap; }
.row > * { flex: 1; min-width: 0; }

.muted { color: var(--ink-soft); }
.tiny { font-size: 12px; }
.center { text-align: center; }
.mono { font-family: var(--mono-font); }