:root {
  --bg: #07080d;
  --panel: #0b0d14;
  --line: rgba(223, 230, 242, 0.09);
  --line-strong: rgba(223, 230, 242, 0.2);
  --text: #eef1f7;
  --dim: #8b93a7;
  --faint: #545c6e;
  --accent: #ffd84a;
  --error: #ff7a6b;
  --blue: #7fb8ff;
  --pw: var(--pw-user, 400px); /* panel width; --pw-user is set by dragging the panel edge */
  --sans: 'Barlow', system-ui, sans-serif;
  --mono: 'JetBrains Mono', ui-monospace, monospace;
  color-scheme: dark;
  /* MathLive virtual keyboard */
  --keyboard-background: #0d1017;
  --keycap-background: #171b25;
  --keycap-background-hover: #222838;
  --keycap-text: #eef1f7;
  --keycap-secondary-background: #222838;
  --keycap-secondary-text: #eef1f7;
  --keyboard-toolbar-text: #eef1f7;
  --keyboard-toolbar-text-active: #ffd84a;
}

/* Light look: dark ink on a light page (the 3D colours live in scene.js LOOKS.light) */
[data-look='light'] {
  --bg: #f4f5f8;
  --panel: #ffffff;
  --line: rgba(27, 34, 51, 0.09);
  --line-strong: rgba(27, 34, 51, 0.22);
  --text: #141a28;
  --dim: #586074;
  --faint: #8a91a2;
  --accent: #b07800;
  --error: #c6372a;
  --blue: #2f6fd6;
  color-scheme: light;
}
[data-look='light'] .primary { background: var(--text); color: #fff; }

/* switching looks crossfades the whole page (see app.js) */
::view-transition-old(root), ::view-transition-new(root) { animation-duration: 0.7s; animation-timing-function: ease-in-out; }
@media (prefers-reduced-motion: reduce) {
  ::view-transition-old(root), ::view-transition-new(root) { animation: none; }
  .describe-note.busy { animation: none; }
}

* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; }
body {
  background: var(--bg);
  color: var(--text);
  font: 400 15px/1.5 var(--sans);
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
}
button, input { font: inherit; color: inherit; }
button { cursor: pointer; }
:focus-visible { outline: 1px solid var(--accent); outline-offset: 2px; }
[hidden] { display: none !important; }
code, kbd, .mono { font-family: var(--mono); font-size: 0.82em; }

/* the big faint layout grid over the whole page */
.layout-grid {
  position: fixed; inset: 0; pointer-events: none; z-index: 5;
  background-image: linear-gradient(var(--line) 1px, transparent 1px), linear-gradient(90deg, var(--line) 1px, transparent 1px);
  background-size: 25vw 33.34vh;
  opacity: 0.5;
}

/* ---------- panel ---------- */
/* dragging the edge scales the panel's contents with its width (--ps = width / 400px) */
.panel > * { zoom: var(--ps, 1); }
.resizer { position: fixed; top: 0; bottom: 0; left: calc(var(--pw) - 4px); width: 8px; z-index: 15; cursor: col-resize; touch-action: none; }
.resizer::after { content: ''; position: absolute; top: 0; bottom: 0; left: 3px; width: 2px; transition: background-color 0.15s; }
.resizer:hover::after, .resizer:focus-visible::after, .resizing .resizer::after { background: var(--accent); }
.resizer:focus-visible { outline: none; }
.resizing { cursor: col-resize; user-select: none; }
.panel {
  position: fixed; top: 0; left: 0; bottom: 0; width: var(--pw);
  overflow-y: auto; overscroll-behavior: contain;
  background: var(--panel);
  border-right: 1px solid var(--line-strong);
  padding: 28px 28px 40px;
  z-index: 10;
  scrollbar-width: thin; scrollbar-color: #2a3040 transparent;
}
.brand { display: flex; gap: 14px; align-items: center; margin-bottom: 30px; }
.mark { width: 38px; height: 38px; fill: none; stroke: var(--accent); stroke-width: 2; }
.brand h1 { margin: 0; font-weight: 300; font-size: 22px; letter-spacing: 0.34em; text-transform: uppercase; line-height: 1.1; }
.brand p { margin: 2px 0 0; color: var(--dim); font-size: 12.5px; letter-spacing: 0.04em; }

section { padding: 18px 0; border-top: 1px solid var(--line); }
.label {
  display: flex; align-items: center; gap: 10px; margin: 0 0 12px;
  font-size: 11px; font-weight: 500; letter-spacing: 0.24em; text-transform: uppercase; color: var(--dim);
}
.label::before { content: ''; width: 3px; height: 13px; background: var(--accent); }

/* equation rows */
.eq-row {
  display: grid; grid-template-columns: 26px 1fr 26px; align-items: center;
  border-bottom: 1px solid var(--line-strong); transition: border-color 0.2s;
}
.eq-row:focus-within { border-bottom-color: var(--accent); }
.eq-idx { font: 500 11px var(--mono); color: var(--accent); }
.eq-row .icon { border: 0; background: none; color: var(--faint); font-size: 18px; padding: 0; width: 26px; height: 26px; }
.eq-row .icon:hover { color: var(--text); }

math-field {
  display: block; width: 100%; min-width: 0;
  background: transparent; color: var(--text); border: 0; outline: 0;
  font-size: 19px; padding: 10px 4px;
  --caret-color: var(--accent);
  --selection-background-color: rgba(255, 216, 74, 0.22);
  --selection-color: var(--text);
  --contains-highlight-background-color: rgba(255, 255, 255, 0.05);
  --primary-color: var(--accent);
  --smart-fence-color: var(--dim);
  --placeholder-color: var(--faint);
}
math-field::part(menu-toggle) { display: none; }
math-field::part(virtual-keyboard-toggle) { color: var(--faint); }

.link { border: 0; background: none; padding: 10px 0 0; color: var(--text); font-size: 13px; letter-spacing: 0.06em; }
.link span { color: var(--faint); }
.link:hover { color: var(--accent); }

/* describe a system in words */
.describe { display: flex; border-bottom: 1px solid var(--line-strong); }
.describe:focus-within { border-bottom-color: var(--accent); }
.describe input { flex: 1; min-width: 0; background: transparent; border: 0; padding: 10px 2px; font-size: 14px; color: var(--text); }
.describe input:focus { outline: none; }
.describe input::placeholder { color: var(--faint); }
.describe-go { border: 0; background: none; padding: 0 4px 0 10px; color: var(--accent); font-size: 11.5px; font-weight: 600; letter-spacing: 0.18em; text-transform: uppercase; }
.describe-note { margin: 8px 0 0; min-height: 1.2em; font-size: 12.5px; color: var(--dim); }
.describe-note.err { color: var(--text); }
.describe-note .hint { border: 0; background: none; padding: 0; color: var(--accent); font-size: inherit; text-align: left; text-decoration: underline dotted; }
.describe-go:disabled { color: var(--faint); cursor: progress; }
.describe-note.busy { animation: pulse 1.4s ease-in-out infinite alternate; }
@keyframes pulse { from { opacity: 1; } to { opacity: 0.45; } }
/* marks a build that came from Claude rather than the built-in reader */
.ai-tag {
  display: inline-block; margin-right: 6px; padding: 0 5px; border: 1px solid var(--blue); color: var(--blue);
  font: 500 10px/16px var(--mono); letter-spacing: 0.08em; text-transform: uppercase; vertical-align: 1px;
}

.status { margin: 12px 0 0; min-height: 1.5em; font: 12px/1.5 var(--mono); color: var(--dim); }
.status.err { color: var(--error); }
.status:not(.err)::before { content: '● '; color: var(--accent); }

/* segmented buttons */
.seg { display: flex; flex-wrap: wrap; gap: 6px; }
.seg button {
  border: 1px solid var(--line-strong); background: transparent; color: var(--dim);
  padding: 7px 12px; font-size: 11.5px; letter-spacing: 0.14em; text-transform: uppercase; transition: 0.15s;
}
.seg button:hover { color: var(--text); border-color: var(--dim); }
.seg button.on { color: var(--text); border-color: var(--accent); background: rgba(255, 216, 74, 0.08); }
.seg.small button { padding: 5px 8px; font-family: var(--mono); letter-spacing: 0; text-transform: none; }

/* initial conditions */
.ic-row { display: grid; grid-template-columns: auto 1fr; align-items: center; gap: 10px; border-bottom: 1px solid var(--line); }
.ic-row:focus-within { border-bottom-color: var(--accent); }
.ic-label { font: 13px var(--mono); color: var(--dim); white-space: nowrap; }
.ic-row math-field { font-size: 16px; padding: 6px 2px; }

.domain { display: flex; align-items: center; gap: 8px; margin-bottom: 12px; font: 13px var(--mono); color: var(--dim); }
.domain input, .param .num {
  width: 74px; background: transparent; border: 0; border-bottom: 1px solid var(--line-strong);
  padding: 4px 2px; font: 13px var(--mono); color: var(--text);
}
.domain input:focus, .param .num:focus { outline: none; border-bottom-color: var(--accent); }

/* parameter sliders */
.param { display: grid; grid-template-columns: 54px 1fr 70px; align-items: center; gap: 12px; padding: 5px 0; }
.param .name { font: italic 17px 'Times New Roman', serif; color: var(--text); overflow: hidden; text-overflow: ellipsis; }
.param .name sub { font-size: 0.65em; font-style: normal; }
.param .num { width: 100%; text-align: right; }
input[type='range'] { -webkit-appearance: none; appearance: none; width: 100%; height: 18px; background: transparent; }
input[type='range']::-webkit-slider-runnable-track { height: 1px; background: var(--line-strong); }
input[type='range']::-moz-range-track { height: 1px; background: var(--line-strong); }
input[type='range']::-webkit-slider-thumb { -webkit-appearance: none; width: 12px; height: 12px; margin-top: -6px; background: var(--bg); border: 2px solid var(--accent); transform: rotate(45deg); }
input[type='range']::-moz-range-thumb { width: 9px; height: 9px; border-radius: 0; background: var(--bg); border: 2px solid var(--accent); transform: rotate(45deg); }

/* examples */
.examples { display: grid; grid-template-columns: 1fr 1fr; gap: 6px; }
.example {
  display: flex; flex-direction: column; align-items: flex-start; gap: 2px; text-align: left;
  padding: 9px 11px; border: 1px solid var(--line); background: rgba(255, 255, 255, 0.015);
  font-size: 13px; transition: 0.15s;
}
.example:hover { border-color: var(--accent); background: rgba(255, 216, 74, 0.05); }
.example small { font: 500 9.5px var(--mono); letter-spacing: 0.18em; color: var(--faint); }
.example:hover small { color: var(--accent); }
.example-group { grid-column: 1 / -1; margin: 10px 0 2px; font-size: 12px; font-weight: 500; letter-spacing: 0.06em; color: var(--text); }
.example-group:first-child { margin-top: 0; }

.help { margin-top: 18px; border-top: 1px solid var(--line); padding-top: 14px; font-size: 13px; color: var(--dim); }
.help summary { cursor: pointer; letter-spacing: 0.06em; color: var(--text); }
.help dl { margin: 12px 0; display: grid; gap: 6px; }
.help dt { color: var(--text); font-size: 12px; letter-spacing: 0.1em; text-transform: uppercase; }
.help dd { margin: 0 0 6px; }
.help code { color: var(--accent); }
kbd { border: 1px solid var(--line-strong); padding: 0 5px; }

/* ---------- viewport ---------- */
.viewport { position: fixed; top: 0; right: 0; bottom: 0; left: var(--pw); }
#stage { display: block; width: 100%; height: 100%; touch-action: none; }

.hud-top {
  position: absolute; top: 26px; left: 32px; right: 270px;
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
  font-size: 12px; letter-spacing: 0.2em; text-transform: uppercase; pointer-events: none;
}
.hud-top .bar { width: 4px; height: 18px; background: var(--accent); }
.dim { color: var(--dim); }

.corner { position: absolute; width: 18px; height: 18px; border: 0 solid var(--line-strong); pointer-events: none; }
.corner.tl { top: 12px; left: 12px; border-width: 1px 0 0 1px; }
.corner.tr { top: 12px; right: 12px; border-width: 1px 1px 0 0; }
.corner.bl { bottom: 12px; left: 12px; border-width: 0 0 1px 1px; }
.corner.br { bottom: 12px; right: 12px; border-width: 0 1px 1px 0; }

.transport {
  position: absolute; left: 32px; bottom: 28px;
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
}
.primary {
  min-width: 128px; padding: 12px 26px; border: 0; border-left: 6px solid var(--accent);
  background: #fff; color: #0b0d14; font-size: 12px; font-weight: 600; letter-spacing: 0.26em; text-transform: uppercase;
}
.primary:hover { background: var(--accent); }
.circle {
  width: 44px; height: 44px; border-radius: 50%; border: 1px solid var(--line-strong); background: transparent;
  display: grid; place-items: center; transition: 0.15s;
}
.circle:hover { border-color: var(--accent); }
.circle svg { width: 18px; height: 18px; fill: none; stroke: currentColor; stroke-width: 1.6; }
#clock { min-width: 90px; color: var(--text); }

.scope {
  position: absolute; right: 32px; bottom: 28px; margin: 0;
  width: 320px; border: 1px solid var(--line-strong); background: color-mix(in srgb, var(--bg) 80%, transparent);
}
/* time axis view: tick labels pinned to 3D points, and the condense control */
.axis-labels { position: absolute; inset: 0; pointer-events: none; overflow: hidden; }
.axis-label { position: absolute; transform: translate(-50%, -50%); font: 11px var(--mono); color: var(--dim); white-space: nowrap; }
.axis-label.axis-name { color: var(--text); font: italic 15px 'Times New Roman', serif; }
.timebox {
  position: absolute; right: 32px; top: 66px; width: 300px; padding: 12px 14px;
  border: 1px solid var(--line-strong); background: color-mix(in srgb, var(--bg) 85%, transparent);
}
.timebox-head { display: flex; justify-content: space-between; align-items: baseline; font-size: 11px; letter-spacing: 0.22em; text-transform: uppercase; color: var(--dim); }
.timebox-head .mono { letter-spacing: 0; text-transform: none; color: var(--text); }
.timebox-ends { display: flex; justify-content: space-between; color: var(--faint); }
#time-reach { margin-top: 6px; }

.s0 { color: var(--accent); }
.s1 { color: var(--text); }
.s2 { color: var(--blue); }
.scope figcaption {
  display: flex; gap: 14px; padding: 6px 10px; border-bottom: 1px solid var(--line);
  background: repeating-linear-gradient(135deg, rgba(255, 255, 255, 0.03) 0 2px, transparent 2px 6px);
  color: var(--dim);
}
#scope { display: block; width: 100%; height: 130px; }

/* top right: 3D/2D switch + Settings */
.top-right { position: fixed; top: 20px; right: 32px; z-index: 20; display: flex; align-items: center; gap: 8px; }
.dims button { min-width: 44px; }
.settings-btn {
  display: flex; align-items: center; gap: 8px; height: 31px; padding: 0 12px;
  border: 1px solid var(--line-strong); background: var(--panel); color: var(--dim);
  font-size: 11.5px; letter-spacing: 0.14em; text-transform: uppercase; transition: 0.15s;
}
.settings-btn:hover, .top-right:has(+ .settings:popover-open) .settings-btn { color: var(--text); border-color: var(--accent); }
.settings-btn svg { width: 16px; height: 16px; fill: none; stroke: currentColor; stroke-width: 1.6; }
.settings {
  position: fixed; inset: auto; top: 62px; right: 32px; margin: 0; width: 300px; padding: 18px 20px;
  background: var(--panel); color: var(--text); border: 1px solid var(--line-strong);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.35);
}
.settings .seg + .label { margin-top: 22px; }
.settings .seg + .key { margin-top: 8px; }
.settings .key {
  width: 100%; padding: 8px 2px; background: transparent; border: 0; border-bottom: 1px solid var(--line-strong);
  font: 12.5px var(--mono); color: var(--text);
}
.settings .key:focus { outline: none; border-bottom-color: var(--accent); }
.settings .key::placeholder { color: var(--faint); }
.settings-note { margin: 10px 0 0; font-size: 12px; line-height: 1.5; color: var(--dim); }
.settings-note a { color: var(--accent); }

/* live readout pinned to the clicked point: the dot sits on the point, the tag above it */
.probe {
  position: absolute; pointer-events: none; white-space: pre; z-index: 2;
  transform: translate(-50%, calc(-100% - 14px));
  padding: 5px 10px; border: 1px solid var(--line-strong); border-left: 3px solid var(--accent);
  background: color-mix(in srgb, var(--panel) 88%, transparent); color: var(--text);
}
.probe::after {
  content: ''; position: absolute; left: 50%; bottom: -18px; width: 8px; height: 8px; margin-left: -4px;
  border-radius: 50%; background: var(--accent); box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 25%, transparent);
}

.toast {
  position: fixed; top: 64px; right: 16px; z-index: 1000;
  padding: 8px 14px; border: 1px solid var(--accent); border-left-width: 4px;
  background: var(--panel); color: var(--text); font: 12px var(--mono);
  box-shadow: 0 6px 24px rgba(0, 0, 0, 0.35);
}

/* ---------- small screens: scene on top, panel below ---------- */
@media (max-width: 820px) {
  :root { --pw: 0px; }
  .resizer { display: none; }
  .panel > * { zoom: 1; }
  .panel { top: 52vh; width: auto; right: 0; border-right: 0; border-top: 1px solid var(--line-strong); padding: 18px 16px 32px; }
  .viewport { bottom: 48vh; }
  .brand { margin-bottom: 14px; }
  .hud-top { top: 16px; left: 16px; right: 170px; font-size: 10.5px; }
  .top-right { top: 10px; right: 12px; }
  .settings-btn span { display: none; }
  .settings { top: 50px; right: 12px; width: min(300px, calc(100vw - 24px)); }
  .transport { left: 16px; bottom: 14px; gap: 10px; }
  .primary { min-width: 0; padding: 10px 16px; }
  #speeds, #rate, .scope { display: none; }
  .layout-grid { background-size: 50vw 26vh; }
}