/* GaussianFeels companion site */

/* ========== Light mode (default) ========== */
:root {
  --bg:              #faf8f5;
  --bg-2:            #f2ece3;
  --bg-3:            #e8e0d5;
  --ink:             #1c1814;
  --ink-2:           #3d3530;
  --ink-3:           #7a6f64;
  --rule:            #ddd7ce;
  --rule-2:          #c8c0b5;
  --tactile:         #b86e28;
  --measure:         #2e6db0;
  --gauss:           #2e8f5c;
  --warn:            #b03020;
  --mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, monospace;
  --serif: 'Inter Tight', Inter, system-ui, sans-serif;
  --sans: Inter, system-ui, sans-serif;
  --dark-panel:      #1e1a17;
  --dark-panel-rule: #2e2a26;
  --dark-panel-ink:  #ede8e2;
  --dark-panel-ink-2:#c0b8b0;
  --dark-panel-ink-3:#7a6f64;
}

/* ========== Dark mode ========== */
[data-theme="dark"] {
  --bg:              #131110;
  --bg-2:            #1a1714;
  --bg-3:            #221e1a;
  --ink:             #ede8e2;
  --ink-2:           #b8b0a8;
  --ink-3:           #786e64;
  --rule:            #2e2924;
  --rule-2:          #3e3830;
  --tactile:         #d98c45;
  --measure:         #4d8fd4;
  --gauss:           #4db87e;
  --warn:            #e06050;
  --dark-panel:      #0c0b09;
  --dark-panel-rule: #1a1714;
  --dark-panel-ink:  #ede8e2;
  --dark-panel-ink-2:#b8b0a8;
  --dark-panel-ink-3:#786e64;
}

/* Smooth theme transitions — only on colour-bearing properties */
body, aside.nav, section, .hero, .card, .video-card,
footer.site, .toc a, .btn, .math-block, .callout,
.thtable td, .thtable th { transition: background-color 0.25s ease, color 0.2s ease, border-color 0.2s ease; }

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; width: 100%; min-height: 100vh; overflow-x: clip; }
body {
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

a { color: var(--ink); text-decoration: underline; text-decoration-color: var(--rule-2); text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { text-decoration-color: var(--tactile); }

::selection { background: #e8c89a; color: #1c1814; }

h1, h2, h3, h4 { font-family: var(--serif); font-weight: 600; letter-spacing: -0.02em; line-height: 1.15; color: var(--ink); }
h1 { font-size: clamp(40px, 6vw, 76px); letter-spacing: -0.035em; }
h2 { font-size: clamp(28px, 3vw, 38px); margin: 0 0 12px; }
h3 { font-size: 20px; margin: 0 0 8px; }
h4 { font-size: 14px; text-transform: uppercase; letter-spacing: 0.12em; font-family: var(--mono); font-weight: 500; color: var(--ink-3); margin: 0 0 12px; }

p { margin: 0 0 16px; text-wrap: pretty; max-width: 70ch; }
small { font-size: 12px; color: var(--ink-3); }
code, .mono { font-family: var(--mono); font-size: 0.92em; }
em { font-style: italic; }
strong { font-weight: 600; }

/* ========== Layout ========== */
.shell {
  display: grid;
  grid-template-columns: 240px 1fr;
  width: 100%;
  min-height: 100vh;
}

aside.nav {
  position: sticky; top: 0; align-self: start;
  height: 100vh; padding: 32px 24px; border-right: 1px solid var(--rule);
  background: var(--bg);
  display: flex; flex-direction: column; gap: 24px;
  overflow-y: auto;
}
.brand { display: flex; flex-direction: column; gap: 8px; }
.brand .title { font-family: var(--serif); font-weight: 650; font-size: 30px; letter-spacing: -0.035em; line-height: 1.05; color: var(--tactile); }
.brand .sub { font-size: 10px; color: var(--ink-3); font-family: var(--mono); letter-spacing: 0.04em; text-transform: uppercase; }

.toc { display: flex; flex-direction: column; gap: 2px; font-family: var(--mono); font-size: 12px; }
.toc a { display: flex; gap: 10px; padding: 6px 8px; border-radius: 4px; text-decoration: none; color: var(--ink-2); align-items: baseline; }
.toc a:hover { background: var(--bg-2); color: var(--ink); }
.toc a.active { background: var(--ink); color: var(--bg); }
.toc a.active .num { color: var(--tactile); }
.toc .num { color: var(--ink-3); width: 22px; flex-shrink: 0; }
.toc-group { display: flex; flex-direction: column; gap: 2px; margin-bottom: 6px; }
.toc-group .group-title { font-size: 10px; letter-spacing: 0.18em; text-transform: uppercase; color: var(--ink-3); padding: 8px 8px 4px; }

.aside-foot { margin-top: auto; font-size: 11px; color: var(--ink-3); font-family: var(--mono); line-height: 1.6; }
.aside-foot .theme-toggle { margin-bottom: 12px; }
.aside-foot a { color: var(--ink-3); }

/* ========== Theme toggle ========== */
.theme-toggle {
  display: flex; align-items: center; gap: 0;
  background: var(--bg-2);
  border: 1px solid var(--rule-2);
  border-radius: 100px;
  padding: 3px;
  cursor: pointer;
  width: 52px; height: 26px;
  position: relative;
  flex-shrink: 0;
  transition: background 0.25s ease, border-color 0.25s ease;
}
.theme-toggle .knob {
  position: absolute;
  width: 20px; height: 20px;
  border-radius: 50%;
  background: var(--ink);
  top: 2px; left: 2px;
  display: flex; align-items: center; justify-content: center;
  transition: transform 0.3s cubic-bezier(0.34, 1.56, 0.64, 1), background 0.25s ease;
}
[data-theme="dark"] .theme-toggle .knob { transform: translateX(26px); }
.theme-toggle .knob svg { width: 11px; height: 11px; stroke: var(--bg); fill: none; stroke-width: 2; stroke-linecap: round; transition: opacity 0.2s ease; }
.theme-toggle .knob .icon-sun  { position: absolute; }
.theme-toggle .knob .icon-moon { position: absolute; }
[data-theme="dark"]  .theme-toggle .knob .icon-sun  { opacity: 0; }
[data-theme="light"] .theme-toggle .knob .icon-moon { opacity: 0; }
[data-theme="dark"]  .theme-toggle .knob .icon-moon { opacity: 1; }
[data-theme="light"] .theme-toggle .knob .icon-sun  { opacity: 1; }

main { min-width: 0; }

section { padding: 96px 64px; border-bottom: 1px solid var(--rule); position: relative; }
section.tight { padding: 64px; }
section.dark { background: var(--dark-panel); color: var(--dark-panel-ink); border-bottom: none; }
section.dark h1, section.dark h2, section.dark h3 { color: var(--dark-panel-ink); }
section.dark h4 { color: var(--dark-panel-ink-3); }
section.dark p { color: var(--dark-panel-ink-2); }
section.dark .figcap { color: var(--dark-panel-ink-3); }
section.dark .math-block { background: #2a2420; color: var(--dark-panel-ink); border-left-color: var(--tactile); }
section.dark .math-block .eq-num { color: var(--dark-panel-ink-3); }

.section-head { display: grid; grid-template-columns: 80px 1fr; gap: 24px; align-items: baseline; margin-bottom: 48px; }
.section-head .num { font-family: var(--mono); font-size: 12px; letter-spacing: 0.15em; color: var(--ink-3); padding-top: 18px; }
.section-head .lead { color: var(--ink-2); font-size: 18px; line-height: 1.5; max-width: 60ch; margin-top: 12px; }

.col { max-width: 720px; }
.col-wide { max-width: 1040px; }

/* ========== Hero ========== */
.hero {
  padding: 80px 64px 96px;
  background:
    radial-gradient(ellipse 700px 350px at 70% 20%, color-mix(in srgb, var(--tactile) 8%, transparent), transparent),
    radial-gradient(ellipse 500px 400px at 15% 85%, color-mix(in srgb, var(--measure) 6%, transparent), transparent),
    var(--bg);
  position: relative;
  overflow: hidden;
}
.hero-meta { display: flex; gap: 16px; font-family: var(--mono); font-size: 11px; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-3); margin-bottom: 32px; flex-wrap: wrap; }
.hero-meta .pill { border: 1px solid var(--rule-2); padding: 4px 10px; border-radius: 100px; }
.hero-meta .pill.live { border-color: var(--tactile); color: var(--tactile); }
.hero-meta .pill.live::before { content: ''; display: inline-block; width: 6px; height: 6px; background: var(--tactile); border-radius: 50%; margin-right: 6px; vertical-align: middle; animation: pulse 1.6s ease-in-out infinite; }
@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.3; } }

.hero h1 { margin: 0 0 28px; max-width: 18ch; }
.hero h1 .accent { color: var(--tactile); }
.hero .deck { font-size: 22px; line-height: 1.5; color: var(--ink-2); max-width: 56ch; margin-bottom: 40px; font-family: var(--serif); font-weight: 400; }

.hero-byline { display: flex; flex-wrap: wrap; gap: 32px 48px; align-items: flex-end; margin-top: 48px; padding-top: 32px; border-top: 1px solid var(--rule); }
.hero-byline .item h4 { margin-bottom: 6px; }
.hero-byline .item .v { font-size: 16px; font-family: var(--serif); }
.hero-byline .item .v small { color: var(--ink-3); display: block; margin-top: 2px; }

.hero-canvas {
  position: absolute; top: 0; right: 0; width: 48%; height: 100%;
  pointer-events: none; opacity: 0.9; background: transparent;
}

/* ========== Figures ========== */
figure { margin: 32px 0; }
figure.full { margin-left: -64px; margin-right: -64px; }
.figcap { font-family: var(--mono); font-size: 11px; letter-spacing: 0.04em; color: var(--ink-3); margin-top: 12px; line-height: 1.6; max-width: 80ch; }
.figcap .figlabel { color: var(--ink); font-weight: 500; }

.frame { border: 1px solid var(--rule); background: var(--bg-2); border-radius: 8px; overflow: hidden; }
.frame.dark { background: var(--dark-panel); border-color: var(--dark-panel-rule); }

/* ========== Cards ========== */
.cards { display: grid; gap: 16px; }
.cards.c2 { grid-template-columns: 1fr 1fr; }
.cards.c3 { grid-template-columns: repeat(3, 1fr); }
.cards.c4 { grid-template-columns: repeat(4, 1fr); }
.card {
  border: 1px solid var(--rule);
  background: var(--bg);
  padding: 24px;
  border-radius: 6px;
  display: flex; flex-direction: column; gap: 8px;
}
.card .label { font-family: var(--mono); font-size: 10px; letter-spacing: 0.15em; color: var(--ink-3); text-transform: uppercase; }
.card .val { font-family: var(--serif); font-size: 36px; font-weight: 500; letter-spacing: -0.02em; }
.card .val .unit { font-size: 16px; color: var(--ink-3); margin-left: 4px; }
.card p { font-size: 13px; color: var(--ink-2); margin: 4px 0 0; }

.tag { display: inline-flex; align-items: center; gap: 6px; padding: 3px 8px; border-radius: 100px; font-family: var(--mono); font-size: 10px; letter-spacing: 0.08em; text-transform: uppercase; }
.tag.tactile { background: color-mix(in srgb, var(--tactile) 12%, transparent); color: var(--tactile); }
.tag.measure { background: color-mix(in srgb, var(--measure) 12%, transparent); color: var(--measure); }
.tag.gauss   { background: color-mix(in srgb, var(--gauss)   15%, transparent); color: var(--gauss); }
.tag.muted   { background: var(--bg-3); color: var(--ink-3); }

/* ========== Tables ========== */
.thtable { width: 100%; border-collapse: collapse; font-size: 13px; font-family: var(--mono); }
.thtable th, .thtable td { text-align: left; padding: 12px 16px; border-bottom: 1px solid var(--rule); vertical-align: top; }
.thtable thead th { font-size: 10px; letter-spacing: 0.15em; text-transform: uppercase; color: var(--ink-3); border-bottom: 1px solid var(--rule-2); font-weight: 500; }
.thtable tbody tr:hover { background: var(--bg-2); }

/* ========== Math ========== */
.math { font-family: 'Latin Modern Math', 'Cambria Math', serif; font-style: italic; }
.math-block {
  font-family: 'Latin Modern Math', 'Cambria Math', serif;
  background: var(--bg-2);
  border-left: 2px solid var(--tactile);
  padding: 20px 24px;
  margin: 24px 0;
  font-size: 17px;
  line-height: 1.9;
  border-radius: 0 6px 6px 0;
  overflow-x: auto;
}
.math-block .eq-num { float: right; color: var(--ink-3); font-family: var(--mono); font-style: normal; font-size: 13px; }

/* ========== Pipeline ========== */
.pipeline { padding: 48px; background: var(--bg-2); border-radius: 8px; border: 1px solid var(--rule); }
.pipeline svg { width: 100%; height: auto; display: block; }

/* ========== Video grid ========== */
.video-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.video-card {
  background: var(--dark-panel);
  color: var(--dark-panel-ink);
  border-radius: 8px; overflow: hidden;
  border: 1px solid var(--dark-panel-rule);
  position: relative;
}
.video-card .stage { aspect-ratio: 16/9; position: relative; overflow: hidden; background: var(--dark-panel); }
.video-card .stage canvas, .video-card .stage video, .video-card .stage img { width: 100%; height: 100%; display: block; object-fit: cover; }
.video-card .meta { padding: 16px 20px; display: flex; justify-content: space-between; gap: 16px; align-items: flex-start; }
.video-card .meta h3 { font-size: 16px; color: var(--dark-panel-ink); margin: 0 0 4px; }
.video-card .meta p { font-size: 12px; color: var(--dark-panel-ink-3); margin: 0; font-family: var(--mono); }
.video-card .meta .play { background: var(--tactile); color: white; border: none; border-radius: 100px; padding: 6px 12px; font-family: var(--mono); font-size: 10px; letter-spacing: 0.1em; text-transform: uppercase; cursor: pointer; flex-shrink: 0; }
.video-card .scrubber { height: 3px; background: #2e2924; position: relative; cursor: pointer; }
.video-card .scrubber .fill { height: 100%; background: var(--tactile); width: 0%; transition: width 0.1s linear; }

.media-slot { position: relative; width: 100%; height: 100%; }
.media-slot[data-state="placeholder"]::after {
  content: 'PLACEHOLDER · drop final media here';
  position: absolute; top: 8px; right: 8px;
  font-family: var(--mono); font-size: 9px; letter-spacing: 0.12em;
  color: rgba(237, 232, 226, 0.5);
  background: rgba(0,0,0,0.35); padding: 3px 8px; border-radius: 100px;
  pointer-events: none;
}

/* ========== Failure cases ========== */
.failure-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.failure { border: 1px solid var(--rule); background: var(--bg); border-radius: 8px; overflow: hidden; }
.failure .top { padding: 16px 20px; display: flex; justify-content: space-between; align-items: center; border-bottom: 1px solid var(--rule); }
.failure .top h3 { font-size: 14px; margin: 0; font-family: var(--mono); font-weight: 500; }
.failure .vis { aspect-ratio: 4/3; background: var(--dark-panel); position: relative; overflow: hidden; }
.failure .vis canvas, .failure .vis video, .failure .vis img { width: 100%; height: 100%; display: block; object-fit: cover; }
.failure .body { padding: 16px 20px; }
.failure .body p { font-size: 13px; margin: 0; color: var(--ink-2); }

/* ========== Status ========== */
.status-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; }
.timeline { display: flex; flex-direction: column; gap: 0; position: relative; }
.timeline::before { content: ''; position: absolute; left: 7px; top: 6px; bottom: 6px; width: 1px; background: var(--rule-2); }
.tl-item { position: relative; padding-left: 32px; padding-bottom: 24px; }
.tl-item::before { content: ''; position: absolute; left: 4px; top: 6px; width: 8px; height: 8px; border-radius: 50%; background: var(--bg); border: 1px solid var(--rule-2); }
.tl-item.done::before { background: var(--gauss); border-color: var(--gauss); }
.tl-item.active::before { background: var(--tactile); border-color: var(--tactile); box-shadow: 0 0 0 4px color-mix(in srgb, var(--tactile) 20%, transparent); }
.tl-item .when { font-family: var(--mono); font-size: 10px; letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-3); }
.tl-item h4 { margin: 4px 0; font-family: var(--serif); text-transform: none; letter-spacing: -0.01em; font-size: 16px; color: var(--ink); }
.tl-item p { font-size: 13px; color: var(--ink-2); margin: 0; }

.progress { background: var(--bg-2); border: 1px solid var(--rule); padding: 24px; border-radius: 8px; }
.progress .row { display: flex; justify-content: space-between; padding: 8px 0; border-bottom: 1px dashed var(--rule); font-family: var(--mono); font-size: 12px; }
.progress .row:last-child { border-bottom: none; }
.progress .row .k { color: var(--ink-2); }
.progress .row .v { color: var(--ink); font-variant-numeric: tabular-nums; }
.bar { height: 6px; background: var(--bg-3); border-radius: 100px; overflow: hidden; margin-top: 4px; }
.bar .fill { height: 100%; background: linear-gradient(90deg, var(--tactile), color-mix(in srgb, var(--tactile) 70%, #f0b060)); border-radius: 100px; }

/* ========== Buttons ========== */
.btn { display: inline-flex; align-items: center; gap: 8px; padding: 10px 16px; border-radius: 100px; border: 1px solid var(--ink); background: var(--ink); color: var(--bg); font-family: var(--mono); font-size: 12px; letter-spacing: 0.08em; text-transform: uppercase; cursor: pointer; text-decoration: none; }
.btn:hover { opacity: 0.88; color: var(--bg); text-decoration: none; }
.btn.ghost { background: transparent; color: var(--ink); }
.btn.ghost:hover { background: var(--ink); color: var(--bg); }
.btn .arrow { transition: transform 0.2s; }
.btn:hover .arrow { transform: translateX(2px); }

/* ========== Footer ========== */
footer.site {
  padding: 48px 64px;
  background: var(--dark-panel);
  color: var(--dark-panel-ink-2);
  font-family: var(--mono); font-size: 12px;
}
footer.site .row { display: flex; justify-content: space-between; gap: 32px; flex-wrap: wrap; }
footer.site a { color: var(--dark-panel-ink); }
footer.site h4 { color: var(--dark-panel-ink); margin-bottom: 12px; }

/* ========== Utility ========== */
.kbd { display: inline-block; padding: 1px 6px; font-family: var(--mono); font-size: 11px; border: 1px solid var(--rule-2); border-bottom-width: 2px; border-radius: 4px; background: var(--bg); color: var(--ink-2); }
.divider { height: 1px; background: var(--rule); margin: 48px 0; }
.callout { border: 1px solid var(--rule-2); background: var(--bg-2); padding: 20px 24px; border-radius: 6px; margin: 32px 0; }
.callout .label { font-family: var(--mono); font-size: 10px; letter-spacing: 0.15em; text-transform: uppercase; color: var(--tactile); margin-bottom: 8px; }
.callout p:last-child { margin-bottom: 0; }

/* ========== Responsive ≤1100px ========== */
@media (max-width: 1100px) {
  .shell { grid-template-columns: 1fr; }
  aside.nav { position: relative; height: auto; border-right: none; border-bottom: 1px solid var(--rule); padding: 24px 32px; }
  section, .hero { padding: 64px 32px; }
  section.tight { padding: 48px 32px; }
  figure.full { margin-left: -32px; margin-right: -32px; }
  .video-grid, .failure-grid, .cards.c3, .cards.c4, .status-grid { grid-template-columns: 1fr; }
  .cards.c2 { grid-template-columns: 1fr; }
  .hero-canvas { display: none; }
  .section-head { grid-template-columns: 1fr; gap: 8px; }
  .section-head .num { padding-top: 0; }
}

/* ========== Responsive ≤900px ========== */
@media (max-width: 900px) {
  aside.nav { flex-direction: row; flex-wrap: wrap; align-items: flex-start; gap: 12px; padding: 16px 24px; }
  .brand { flex: 1 1 180px; }
  .toc { flex: 2 1 280px; flex-direction: row; flex-wrap: wrap; gap: 4px; }
  .toc-group { margin-bottom: 0; }
  .toc-group .group-title { display: none; }
  .aside-foot { display: none; }
  section, .hero { padding: 48px 28px; }
  section.tight { padding: 36px 28px; }
  figure.full { margin-left: -28px; margin-right: -28px; }
  .failure-grid { grid-template-columns: 1fr 1fr; }
  .cards.c3, .cards.c4 { grid-template-columns: 1fr 1fr; }
}

/* ========== Responsive ≤600px ========== */
@media (max-width: 600px) {
  aside.nav { padding: 14px 16px; }
  .toc { display: none; }
  section, .hero { padding: 36px 18px; }
  section.tight { padding: 28px 18px; }
  footer.site { padding: 36px 18px; }
  footer.site .row { flex-direction: column; gap: 24px; }
  figure.full { margin-left: -18px; margin-right: -18px; }
  h1 { font-size: clamp(26px, 8vw, 42px); }
  h2 { font-size: clamp(20px, 5vw, 28px); }
  .hero .deck { font-size: 17px; }
  .hero-byline { gap: 20px; }
  .cards.c2, .cards.c3, .cards.c4 { grid-template-columns: 1fr; }
  .failure-grid { grid-template-columns: 1fr; }
  .video-grid { grid-template-columns: 1fr; }
  .status-grid { grid-template-columns: 1fr; }
  .pipeline { padding: 20px 14px; }
  .math-block { padding: 14px 16px; font-size: 14px; }
  .thtable { font-size: 12px; }
  .thtable th, .thtable td { padding: 8px 10px; }
  .card > div[style*="justify-content:space-between"] { flex-direction: column; align-items: flex-start; }
}