/* css/components.css
   Shell chrome and generic components shared by every station.
   Rule: no colour literals here. Colours come from tokens (var(--...)), plus the keywords
   transparent, currentColor and inherit. Mixed tints use color-mix() with a plain fallback
   declared first. Widget-specific styles (plane, explainer, staircase, domain colouring,
   3D view) are injected by their own modules, not here. */

/* ============================================================
   1. Utilities
   ============================================================ */

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  top: var(--space-2);
  left: var(--space-2);
  z-index: 100;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  background: var(--accent);
  color: var(--on-accent);
  font-weight: 600;
  text-decoration: none;
  transform: translateY(-200%);
}

.skip-link:focus {
  transform: none;
}

.stack > * + * { margin-top: var(--space-3); }
.row { display: flex; flex-wrap: wrap; align-items: center; gap: var(--space-2) var(--space-3); }
.grow { flex: 1 1 auto; min-width: 0; }
.muted { color: var(--text-muted); }
.mono { font-family: var(--font-mono); }
.nowrap { white-space: nowrap; }

/* Tone: the two-address colour code. data-tone sets --tone for borders, sliders and marks.
   .tone-* colours text. Cartesian = blue, polar = orange, input = green, output = purple. */
[data-tone="cart"], [data-thread="T1"] { --tone: var(--cart); }
[data-tone="polar"], [data-thread="T2"] { --tone: var(--polar); }
[data-tone="input"] { --tone: var(--input); }
[data-tone="output"], [data-thread="T3"], [data-thread="F1"] { --tone: var(--output); }
[data-thread="F2"] { --tone: var(--cart); }
[data-thread="F3"] { --tone: var(--input); }
[data-tone="accent"] { --tone: var(--accent); }
.tone-cart { color: var(--cart); }
.tone-polar { color: var(--polar); }
.tone-input { color: var(--input); }
.tone-output { color: var(--output); }

/* Touch: no double-tap zoom delay on controls, no grey tap flash. */
.btn, .chip, .icon-btn, .nav-link, .station-link, summary {
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

/* ============================================================
   2. Shell: header, navigation, view, footer
   ============================================================ */

body {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  grid-template-rows: auto 1fr auto;
  grid-template-areas:
    "header"
    "main"
    "footer";
}

.site-header {
  grid-area: header;
  position: sticky;
  top: 0;
  z-index: 30;
  height: var(--header-h);
  border-bottom: 1px solid var(--border);
  background: var(--bg);
}

.site-header-inner {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  height: 100%;
  padding: 0 var(--gutter);
}

.brand {
  flex: 1 1 auto;
  min-width: 0;
  display: flex;
  align-items: center;
}

.site-title {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  min-width: 0;
  color: var(--text);
  text-decoration: none;
}

.site-title:hover .site-title-text {
  text-decoration: underline;
  text-decoration-thickness: 0.08em;
  text-underline-offset: 0.2em;
}

.brand-mark {
  flex: none;
  width: 1.9rem;
  height: 1.9rem;
}

.brand-mark .mark-axis { stroke: var(--text-muted); fill: none; stroke-width: 1.4; stroke-linecap: round; }
.brand-mark .mark-wedge { fill: var(--polar); }
.brand-mark .mark-cart { stroke: var(--cart); fill: none; stroke-width: 3.2; stroke-linecap: round; stroke-linejoin: round; }
.brand-mark .mark-polar { stroke: var(--polar); fill: none; stroke-width: 3.2; stroke-linecap: round; }
.brand-mark .mark-dot { fill: var(--text); }

.site-title-text {
  overflow: hidden;
  font-family: var(--font-display);
  font-size: clamp(1rem, 0.9rem + 0.9vw, 1.3rem);
  font-weight: 600;
  line-height: 1.2;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.header-actions {
  flex: none;
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: none;
  width: var(--tap);
  height: var(--tap);
  padding: 0;
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
}

.icon-btn:hover { background: var(--surface-2); }
.icon-btn svg { width: 1.35rem; height: 1.35rem; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }

/* The sun shows in dark mode (click for light), the moon in light mode. Both come from tokens. */
.icon-btn .icon-sun { display: var(--icon-sun); }
.icon-btn .icon-moon { display: var(--icon-moon); }

.nav-toggle[aria-expanded="true"] {
  background: var(--surface-2);
  border-color: var(--text);
}

/* Navigation: a drawer on phones, a sticky sidebar from 900px up. */
.site-nav {
  display: none;
  position: fixed;
  top: var(--header-h);
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 25;
  padding: var(--space-3) var(--gutter) var(--space-5);
  overflow-y: auto;
  overscroll-behavior: contain;
  border-top: 1px solid var(--border);
  background: var(--surface);
}

body[data-nav-open="true"] .site-nav {
  display: block;
}

/* The open drawer covers the page, so the page behind it must not scroll under a thumb.
   (The JS also marks #view and the footer inert, so Tab cannot wander into them.) */
body[data-nav-open="true"] {
  overflow: hidden;
}

.site-nav :focus-visible { outline-offset: -3px; }

.map-switch-block { margin: 0 0 var(--space-3); }
.map-switch-label {
  margin: 0 0 var(--space-1);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--text-muted);
}
.map-switch { display: flex; flex-wrap: wrap; gap: var(--space-2); margin: 0; }
.nav-map { padding: 0 var(--space-2); }

.nav-part + .nav-part { margin-top: var(--space-3); }

.nav-part-title {
  display: flex;
  align-items: baseline;
  gap: var(--space-2);
  margin: 0 0 var(--space-1);
  padding: 0 var(--space-2);
  font-family: var(--font);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  line-height: 1.3;
  text-transform: uppercase;
  color: var(--text-muted);
}

.nav-part-roman { min-width: 1.6em; }
.nav-part-note { margin-left: auto; font-weight: 500; letter-spacing: 0.02em; text-transform: none; }

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

.nav-link {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-height: var(--tap);
  padding: var(--space-1) var(--space-2);
  border-left: 3px solid transparent;
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  color: var(--text);
  font-size: 0.97rem;
  line-height: 1.25;
  text-decoration: none;
}

.nav-link:hover { background: var(--surface-2); }

.nav-link[aria-current="page"] {
  border-left-color: var(--accent);
  background: var(--surface-2);
  font-weight: 700;
}

.nav-num {
  flex: none;
  min-width: 1.5em;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.8rem;
  text-align: right;
}

.nav-title { flex: 1 1 auto; min-width: 0; }

.nav-threads { flex: none; display: inline-flex; gap: 3px; }

/* A thread dot: solid for T1 and T3, a dashed ring for T2 (so colour is never the only cue). */
.thread-dot {
  display: inline-block;
  box-sizing: border-box;
  width: 0.62rem;
  height: 0.62rem;
  border: 2px solid var(--tone, var(--text-muted));
  border-radius: 50%;
  background: var(--tone, var(--text-muted));
}

.thread-dot[data-thread="T2"],
.thread-dot[data-thread="F2"] {
  border-style: dashed;
  background: transparent;
}

/* T3 and F3 are diamonds, so three threads differ by shape as well as hue. */
.thread-dot[data-thread="T3"],
.thread-dot[data-thread="F3"] {
  border-radius: 1px;
  transform: rotate(45deg) scale(0.78);
}

#view {
  grid-area: main;
  width: 100%;
  max-width: var(--content-max);
  min-width: 0;
  margin: 0 auto;
  padding: var(--space-4) var(--gutter) var(--space-5);
}

#view:focus { outline: none; }

.site-footer {
  grid-area: footer;
  width: 100%;
  max-width: var(--content-max);
  min-width: 0;
  margin: 0 auto;
  padding: var(--space-3) var(--gutter) var(--space-4);
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.92rem;
}

.site-footer p { margin: 0 0 var(--space-2); }

@media (min-width: 56.25rem) {
  body {
    grid-template-columns: var(--sidebar-w) minmax(0, 1fr);
    grid-template-areas:
      "header header"
      "nav main"
      "nav footer";
  }

  .site-header-inner { padding: 0 var(--space-4); }

  .nav-toggle { display: none; }

  .site-nav {
    display: block;
    grid-area: nav;
    position: sticky;
    top: var(--header-h);
    right: auto;
    bottom: auto;
    left: auto;
    z-index: 1;
    align-self: start;
    height: calc(100vh - var(--header-h));
    height: calc(100dvh - var(--header-h));
    padding: var(--space-3) var(--space-2) var(--space-5);
    border-top: 0;
    border-right: 1px solid var(--border);
    background: var(--bg);
  }

  #view { padding: var(--space-4) var(--space-4) var(--space-5); }
  .site-footer { padding-left: var(--space-4); padding-right: var(--space-4); }
}

/* ---------- colour key (footer) ---------- */

.colour-key summary {
  min-height: var(--tap);
  display: flex;
  align-items: center;
  color: var(--text);
  font-weight: 600;
  cursor: pointer;
}

/* display:flex on a summary removes the browser's disclosure triangle, so draw a chevron:
   without it "Colour key" and "What went wrong" read as plain labels, not as controls. */
.colour-key summary::before,
.error-details summary::before {
  content: "";
  flex: none;
  width: 0.5em;
  height: 0.5em;
  margin-right: 0.7em;
  border-right: 2px solid currentcolor;
  border-bottom: 2px solid currentcolor;
  transform: rotate(-45deg);
}

.colour-key[open] > summary::before,
.error-details[open] > summary::before {
  transform: rotate(45deg);
}

.colour-key-list {
  display: grid;
  gap: var(--space-2) var(--space-4);
  margin: var(--space-2) 0 0;
  padding: 0;
  list-style: none;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 19rem), 1fr));
}

/* Test 2 uses blue, orange, purple and green for the two pictures, one meaning each.
   The map legend names F1–F3. The Test 1 key stays in the page and is hidden on this map. */
.source-tag {
  margin: var(--space-2) 0 0;
  color: var(--text-muted);
  font-size: 0.82rem;
  line-height: 1.4;
  overflow-wrap: anywhere;
}
.source-tag a { color: inherit; }
.scope-banner {
  margin: 0 0 var(--space-3);
  padding: var(--space-2) var(--space-3);
  border-left: 4px solid var(--warn);
  background: var(--surface-2);
  overflow-wrap: anywhere;
}
.scope-banner[data-scope="possible"] { border-left-color: var(--text-muted); }
.walk-list { margin: var(--space-2) 0 0; padding-left: 1.4rem; font-family: var(--font-mono); font-size: 0.92rem; }
.walk-list li { margin: 0.15rem 0; overflow-wrap: anywhere; }
.added-check { margin-top: var(--space-2); padding: var(--space-2) var(--space-3); border-left: 4px solid var(--input); background: var(--surface-2); }
.book-answer { margin-top: var(--space-2); padding: var(--space-2) var(--space-3); border-left: 4px solid var(--accent); background: var(--surface-2); }

/* Test 1 keeps Arg, the seam, the time ramp, and T1–T3. Test 2 home is the pair.
   Julia and Newton each tell the colours on that picture. */
#colour-key-test2,
#colour-key-julia,
#colour-key-newton { display: none; }
body[data-map="test2"] #colour-key-test1 { display: none; }
body[data-map="test2"]:not([data-station="julia"]):not([data-station="newton"]) #colour-key-test2 { display: grid; }
body[data-map="test2"][data-station="julia"] #colour-key-julia { display: grid; }
body[data-map="test2"][data-station="newton"] #colour-key-newton { display: grid; }

.colour-key-list li {
  display: grid;
  grid-template-columns: 3.2rem minmax(0, 1fr);
  align-items: start;
  gap: var(--space-2);
  color: var(--text);
  font-size: 0.92rem;
  line-height: 1.4;
}

.key-swatch {
  display: block;
  width: 3.2rem;
  height: 1.1rem;
  margin-top: 0.15rem;
  border-radius: 3px;
}

.key-swatch[data-key="cart"] { background: var(--cart); }
.key-swatch[data-key="polar"] { background: var(--polar); }
.key-swatch[data-key="input"] { background: var(--input); }
.key-swatch[data-key="output"] { background: var(--output); }
.key-swatch[data-key="ramp"] { background: linear-gradient(90deg, var(--t0), var(--t1)); }
.key-line { display: block; width: 3.2rem; height: 1.1rem; margin-top: 0.15rem; overflow: visible; }
.key-line line { stroke-width: 2.4; stroke-linecap: round; }
.key-line path { fill: none; stroke-linecap: round; }
/* arg versus Arg: a neutral axis and ray, then ONE solid arc (Arg z) or a stack of faint arcs
   (the other members of the set arg z). The ghost arcs are one path, so the fade is applied once. */
.key-line .key-axis { stroke: var(--border-strong); stroke-width: 1.4; }
.key-line .arg-home { stroke: var(--polar); stroke-width: 2.8; }
.key-line .arg-ghost { stroke: var(--polar); stroke-width: 1.9; opacity: var(--ghost-alpha); }
.key-line .seam-line { stroke: var(--seam); stroke-dasharray: 5 4; stroke-width: 2; }
.key-line .thread-t1 { stroke: var(--cart); }
.key-line .thread-t2 { stroke: var(--polar); stroke-dasharray: 5 4; }
.key-line .thread-t3 { stroke: var(--output); stroke-dasharray: 0.1 5.2; stroke-width: 3; }

/* ============================================================
   3. Station chrome (the header every station starts with, and the links it ends with)
   ============================================================ */

.station {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  min-width: 0;
}

.station > * { min-width: 0; }

.station-header h1 { margin-bottom: var(--space-2); }

.station-lede {
  max-width: 62ch;
  margin: 0 0 var(--space-3);
  color: var(--text-muted);
  font-size: 1.05rem;
}

/* Textbook line under the lede. Hidden until book, chapter, and section are all named. */
.station-source {
  max-width: 62ch;
  margin: -0.5rem 0 var(--space-3);
  color: var(--text-muted);
  font-size: 0.88rem;
}
.station-source[hidden] { display: none; }

.thread-badges { display: flex; flex-wrap: wrap; gap: var(--space-2); margin: 0 0 var(--space-2); padding: 0; list-style: none; }

.thread-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.1rem 0.65rem 0.1rem 0.5rem;
  border: 1.5px solid var(--tone, var(--border-strong));
  border-radius: 999px;
  background: var(--surface);
  color: var(--text);
  font-size: 0.82rem;
  font-weight: 600;
  line-height: 1.6;
}

.thread-badge::before {
  content: "";
  box-sizing: border-box;
  width: 0.6rem;
  height: 0.6rem;
  border: 2px solid var(--tone, var(--text-muted));
  border-radius: 50%;
  background: var(--tone, var(--text-muted));
}

.thread-badge[data-thread="T2"]::before,
.thread-badge[data-thread="F2"]::before { border-style: dashed; background: transparent; }
.thread-badge[data-thread="T3"]::before,
.thread-badge[data-thread="F3"]::before { border-radius: 1px; transform: rotate(45deg) scale(0.78); }
.problem-card.is-target { outline: 2px solid var(--focus); outline-offset: 2px; }

.station-links {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2) var(--space-3);
  padding-top: var(--space-3);
  border-top: 1px solid var(--border);
}

.station-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  min-height: var(--tap);
  padding: 0 var(--space-3);
  border: 1.5px solid var(--tone, var(--border-strong));
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
  text-decoration: none;
}

.station-link:hover { background: var(--surface-2); }
.station-link[data-dir="prev"]::before { content: "\2190"; }
.station-link[data-dir="next"]::after { content: "\2192"; }

/* ============================================================
   4. Components
   ============================================================ */

.panel {
  padding: var(--space-3) var(--space-3) var(--space-3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow);
}

.panel[data-tone] { border-top: 4px solid var(--tone); }
.panel-title { margin-bottom: var(--space-2); }
.panel-subtitle { margin: var(--space-4) 0 var(--space-2); }
.lede { font-size: 1.1rem; }

.card-grid {
  display: grid;
  gap: var(--space-3);
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 21rem), 1fr));
}

.card {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  min-width: 0;
  padding: var(--space-3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
}

.card[data-tone] { border-left: 4px solid var(--tone); }

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  min-height: var(--tap);
  padding: 0 var(--space-3);
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
  font-weight: 600;
  line-height: 1.2;
  text-align: center;
  text-decoration: none;
  cursor: pointer;
}

.btn:hover { background: var(--surface-2); }
.btn:active { transform: translateY(1px); }
.btn[disabled], .btn[aria-disabled="true"] { opacity: 0.55; cursor: not-allowed; transform: none; }
.btn-primary { border-color: var(--accent); background: var(--accent); color: var(--on-accent); }
.btn-primary:hover { background: var(--accent); filter: brightness(1.12); }
.btn-quiet { border-color: transparent; background: transparent; }
.btn-quiet:hover { border-color: var(--border-strong); }

/* Chips: modes, presets, problem links. Pressed or active chips get a tinted fill. */
.chips { display: flex; flex-wrap: wrap; gap: var(--space-2); margin: 0; padding: 0; list-style: none; }

.chip {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  min-height: 2.25rem;
  padding: 0.1rem 0.85rem;
  border: 1.5px solid var(--tone, var(--border-strong));
  border-radius: 999px;
  background: var(--surface);
  color: var(--text);
  font-size: 0.95rem;
  line-height: 1.2;
  text-decoration: none;
  cursor: pointer;
}

button.chip { min-height: var(--tap); }
.chip:hover { background: var(--surface-2); }

.chip[aria-pressed="true"],
.chip[aria-selected="true"],
.chip[aria-current="true"],
.chip.is-active {
  border-color: var(--tone, var(--accent));
  background: var(--surface-2);
  box-shadow: inset 0 0 0 1px var(--tone, var(--accent));
  font-weight: 700;
}

@supports (background: color-mix(in srgb, currentColor 10%, transparent)) {
  .chip[aria-pressed="true"],
  .chip[aria-selected="true"],
  .chip[aria-current="true"],
  .chip.is-active {
    background: color-mix(in srgb, var(--tone, var(--accent)) 16%, var(--surface));
  }
}

/* A chip that answers a question: solid border for yes, dashed for no (shape, not just colour). */
.chip[data-answer="yes"] { border-color: var(--ok); border-style: solid; }
.chip[data-answer="no"] { border-color: var(--text-muted); border-style: dashed; }

.problem-chip { min-height: 2rem; font-family: var(--font-mono); font-size: 0.88rem; }

/* Sliders: label, range, value */
.step-control {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) 6.2rem;
  gap: 0.35rem 0.6rem;
  align-items: center;
  margin: var(--space-2) 0 0;
  padding: 0;
  border: 0;
  min-width: 0;
  max-width: 100%;
}
.step-control .step-label {
  font-weight: 600;
  padding: 0;
}
.step-control input[type="range"] {
  width: 100%;
  min-width: 0;
  margin: 0;
}
.step-control input[type="text"] {
  width: 100%;
  min-width: 0;
  font-family: var(--font-mono);
}
.step-readout {
  grid-column: 1 / -1;
  font-family: var(--font-mono);
  color: var(--text-muted);
  font-size: max(0.94rem, 15px);
}
.step-hint {
  grid-column: 1 / -1;
  margin: 0;
  color: var(--polar);
  font-size: max(0.94rem, 15px);
}
.step-hint[hidden] { display: none; }
.step-control .btn { grid-column: 1 / -1; justify-self: start; }
@media (max-width: 26rem) {
  .step-control { grid-template-columns: minmax(0, 1fr) 6.2rem; }
  .step-control .step-label { grid-column: 1 / -1; }
}

.matrix-board { display: grid; gap: var(--space-4); min-width: 0; }
.matrix-row { min-width: 0; }
.matrix-row-title { margin: 0 0 var(--space-1); font-size: 1.05rem; }
.matrix-row-note { margin: 0 0 var(--space-2); color: var(--text-muted); font-size: max(0.94rem, 15px); }
.matrix-row .chips { margin: 0; }

.slider-row {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: var(--space-1) var(--space-3);
  min-height: var(--tap);
}

.slider-row > label { font-weight: 600; }

.slider-row input[type="range"] {
  width: 100%;
  min-width: 0;
  height: var(--tap);
  margin: 0;
  accent-color: var(--tone, var(--accent));
  cursor: pointer;
}

.slider-row output,
.slider-row .slider-value {
  min-width: 3.5em;
  color: var(--text-muted);
  font-family: var(--font-mono);
  font-size: 0.92rem;
  text-align: right;
}

@media (max-width: 30rem) {
  .slider-row { grid-template-columns: minmax(0, 1fr) auto; }
  .slider-row input[type="range"] { grid-column: 1 / -1; grid-row: 2; }
}

/* Form fields */
.field { display: inline-flex; flex-direction: column; gap: var(--space-1); min-width: 0; }
.field > label, .field-label { color: var(--text-muted); font-size: 0.88rem; font-weight: 600; }

input:not([type="range"]):not([type="checkbox"]):not([type="radio"]),
select,
textarea {
  min-height: var(--tap);
  max-width: 100%;
  padding: 0 var(--space-2);
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text);
}

textarea { padding: var(--space-2); }
input[type="number"], input.num { width: 7.5rem; font-family: var(--font-mono); }
input[type="checkbox"], input[type="radio"] { width: 1.25rem; height: 1.25rem; margin: 0; accent-color: var(--accent); }

.check {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  min-height: var(--tap);
  cursor: pointer;
}

/* Readout: the plain-text line interaction scripts read. Monospace, wraps, never overflows. */
.readout {
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface-2);
  color: var(--text);
  font-family: var(--font-mono);
  font-size: 0.92rem;
  line-height: 1.5;
  overflow-wrap: anywhere;
  white-space: pre-wrap;
}

/* Two planes: two columns when the view is at least 760px wide, stacked below. */
.two-planes {
  display: grid;
  gap: var(--space-3);
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 23.25rem), 1fr));
}

.two-planes > * { min-width: 0; }

/* Callouts and badges */
.callout {
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--border);
  border-left: 4px solid var(--tone, var(--accent));
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  background: var(--surface);
}

.callout > :last-child { margin-bottom: 0; }

.badge {
  display: inline-block;
  padding: 0 0.5rem;
  border: 1.5px solid var(--tone, var(--border-strong));
  border-radius: 4px;
  color: var(--text);
  font-size: 0.78rem;
  font-weight: 700;
  line-height: 1.5;
  letter-spacing: 0.03em;
}

/* Math fallbacks and wide formulas scroll inside their own box, never the page. */
.tex-error { color: var(--danger); font-family: var(--font-mono); }
.katex-display { max-width: 100%; overflow-x: auto; overflow-y: hidden; padding: 0.15em 0; }
.tex-scroll { max-width: 100%; overflow-x: auto; }

/* An exponent set by prose() (katex.js) or the menu: readable inside chips, buttons and links, and it never stretches the line. */
sup.prose-sup { font-size: 0.85em; line-height: 0; }

/* Router states */
.loading {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-4) 0;
  color: var(--text-muted);
}

.spinner {
  width: 1.1rem;
  height: 1.1rem;
  border: 3px solid var(--border-strong);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: mv-spin 0.9s linear infinite;
}

@keyframes mv-spin { to { transform: rotate(360deg); } }

.under-construction { border-left: 6px solid var(--warn); }
.fatal { border-left: 6px solid var(--danger); }
.error-details { margin-top: var(--space-3); }
.error-details summary { min-height: var(--tap); display: flex; align-items: center; cursor: pointer; }

.route-token { overflow-wrap: anywhere; }

.place-list { margin: 0; padding: 0; list-style: none; display: grid; gap: var(--space-2) var(--space-4); grid-template-columns: repeat(auto-fit, minmax(min(100%, 22rem), 1fr)); }
.place-list li { min-width: 0; padding-bottom: var(--space-2); border-bottom: 1px solid var(--border); }
.place-link { display: flex; gap: var(--space-2); align-items: baseline; color: var(--text); font-weight: 700; text-decoration: none; }
.place-link:hover .place-title { text-decoration: underline; }
.place-num { flex: none; min-width: 1.6em; color: var(--text-muted); font-family: var(--font-mono); font-size: 0.85rem; text-align: right; }
.place-summary { display: block; margin-left: calc(1.6em + var(--space-2)); color: var(--text-muted); font-size: 0.9rem; line-height: 1.4; }

/* ---------------------------------------------------------------- film panel (js/core/film.js)
   A 1280 x 720 HyperFrames page. At 835px and wider the stage scales design rows 0 to 600
   (content above 548, one cite at 560). 835 keeps the 23px cite at 15px. Under 835px the
   page stacks: plane, then staircase or lines, and the stage grows to that height.
   Nothing scrolls sideways. Text in either layout stays at 15px or more. */
.film-block { display: grid; gap: var(--space-4, 16px); margin: var(--space-4, 16px) 0; min-width: 0; }
.film { min-width: 0; }
[data-film-slot] { min-width: 0; }
.film-stage {
  position: relative;
  width: 100%;
  max-width: 100%;
  min-width: 0;
  aspect-ratio: 1280 / 600;
  overflow: hidden;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--bg);
}
.film-scaler { position: relative; height: 100%; overflow: hidden; }
.film-frame {
  position: absolute;
  left: 0;
  top: 0;
  width: 1280px;
  height: 720px;
  border: 0;
  transform-origin: 0 0;
  pointer-events: none;
}
.film-wait { position: absolute; inset: auto 0 0 0; margin: 0; padding: 8px 12px; color: var(--text-muted); }
.film-controls { grid-template-columns: auto minmax(0, 1fr) auto; }
.film-controls output { font-variant-numeric: tabular-nums; min-width: 13ch; text-align: right; white-space: nowrap; }
.film-readout { white-space: pre-line; font-variant-numeric: tabular-nums; min-height: 3.2em; }
.film-readout:empty { display: none; }
.film-lede { max-width: 70ch; }
@media (max-width: 30rem) {
  .film-controls.slider-row { grid-template-columns: minmax(0, 1fr) auto; }
  .film-controls.slider-row .film-play { grid-column: 1; grid-row: 1; justify-self: start; }
  .film-controls.slider-row output { grid-column: 2; grid-row: 1; }
  .film-controls.slider-row input[type="range"] { grid-column: 1 / -1; grid-row: 2; }
}