/* ──────────────────────────────────────────────────────────────────
   Xiaobo · pretext notebook — minimalist print + dynamic typography
   ────────────────────────────────────────────────────────────────── */

:root {
  --paper:        #fafaf7;
  --paper-soft:   #f3f1ea;
  --ink:          #1a1a1a;
  --muted:        #6b6b67;
  --rule:         #d8d2bf;
  --rule-soft:    #ece7d4;
  --accent:       #b34a36;
  --accent-soft:  #d6826f;
  --gold:         #c8a85b;

  --serif:  "Source Serif 4", "Source Serif Pro", "EB Garamond",
            "Iowan Old Style", Cambria, Georgia, serif;
  --display: "Fraunces", "Source Serif 4", "EB Garamond",
             "Iowan Old Style", Georgia, serif;
  --sans:   Inter, -apple-system, system-ui, "Segoe UI", Helvetica, Arial,
            sans-serif;
  --mono:   "JetBrains Mono", "SF Mono", Menlo, Consolas, monospace;

  --col:  66ch;
  --gut:  8vw;
  --line: 1.65;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper:       #16140f;
    --paper-soft:  #1f1c14;
    --ink:         #ece6d3;
    --muted:       #a09a86;
    --rule:        #3a352a;
    --rule-soft:   #2a261c;
    --accent:      #d6826f;
    --accent-soft: #b34a36;
    --gold:        #d8b86b;
  }
  .post__body pre,
  .code-block pre { filter: invert(0.92) hue-rotate(180deg); }
  .figure img { box-shadow: 0 1px 3px rgba(0, 0, 0, 0.4); }
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  line-height: var(--line);
  font-size: clamp(15px, 0.55vw + 13px, 18px);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  font-feature-settings: "kern", "liga", "onum";
}

a {
  color: inherit;
  text-decoration: underline;
  text-decoration-color: var(--rule);
  text-decoration-thickness: 0.06em;
  text-underline-offset: 0.2em;
  transition: text-decoration-color 0.2s ease;
}
a:hover { text-decoration-color: var(--accent); }

.skip {
  position: absolute;
  left: -10000px;
  top: auto;
  width: 1px;
  height: 1px;
  overflow: hidden;
}
.skip:focus {
  left: 1rem;
  top: 1rem;
  width: auto;
  height: auto;
  padding: 0.5rem 0.8rem;
  background: var(--ink);
  color: var(--paper);
  z-index: 9999;
}

/* ───────── masthead ───────── */
.masthead {
  max-width: 1100px;
  margin: 4vh auto 0;
  padding: 0 var(--gut);
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.18em;
  color: var(--muted);
  text-transform: uppercase;
}
.masthead__rule {
  height: 1px;
  background: var(--rule);
  transform-origin: left;
  animation: ruleIn 1.2s cubic-bezier(0.2, 0.7, 0.3, 1) forwards;
}
.masthead__author {
  display: block;
  font-family: var(--display);
  font-weight: 460;
  text-transform: none;
  letter-spacing: 0.02em;
  font-size: 1.1rem;
  color: var(--ink);
  text-decoration: none;
  text-align: center;
  padding: 1.1rem 0 0.9rem;
  font-variation-settings: "opsz" 60, "SOFT" 30;
}
.masthead__meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 0 1rem;
}
.masthead__meta .vol { color: var(--muted); }
.lang-toggle a {
  color: var(--muted);
  text-decoration: none;
  margin-left: 0.4em;
}
.lang-toggle a:hover { color: var(--accent); }

@keyframes ruleIn {
  from { transform: scaleX(0); }
  to   { transform: scaleX(1); }
}

/* ───────── hero ───────── */
.hero {
  max-width: 1100px;
  margin: 0 auto;
  padding: 9vh var(--gut) 5vh;
  text-align: center;
}
.eyebrow {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.32em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 1.4rem;
}
.hero__title {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2.4rem, 8.5vw, 6rem);
  letter-spacing: 0.05em;
  line-height: 1.02;
  margin: 0 auto;
  text-rendering: geometricPrecision;
}
.hero__tagline {
  font-family: var(--serif);
  font-style: italic;
  font-size: clamp(1.05rem, 1.6vw, 1.4rem);
  color: var(--muted);
  margin: 1.8rem auto 0;
  line-height: 1.45;
  max-width: 36ch;
}
.hero__hairline {
  width: 0;
  height: 1px;
  background: var(--accent);
  margin: 3.2rem auto 0;
  animation: drawIn 1.4s 0.4s cubic-bezier(0.2, 0.7, 0.3, 1) forwards;
}
@keyframes drawIn {
  from { width: 0; }
  to   { width: 4rem; }
}

/* ───────── home table-of-contents ───────── */
.toc {
  max-width: 56rem;
  margin: 0 auto;
  padding: 5vh var(--gut) 8vh;
}
.toc__h {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.32em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 2rem;
  display: flex;
  justify-content: space-between;
  align-items: baseline;
}
.toc__h .count { color: var(--rule); }
.toc__list { list-style: none; margin: 0; padding: 0; }
.toc__item {
  padding: 1.8rem 0 1.6rem;
  border-top: 1px solid var(--rule);
}
.toc__item:last-child { border-bottom: 1px solid var(--rule); }

/* Scroll-in stagger. Only applied when JS marks the list with .is-armed —
   without JS the items render at rest, so reduced-motion or no-JS is fine. */
.toc__list.is-armed .toc__item {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 700ms cubic-bezier(0.2, 0.7, 0.3, 1),
              transform 700ms cubic-bezier(0.2, 0.7, 0.3, 1);
}
.toc__list.is-armed .toc__item.is-in {
  opacity: 1;
  transform: none;
}
@media (prefers-reduced-motion: reduce) {
  .toc__list.is-armed .toc__item,
  .toc__list.is-armed .toc__item.is-in {
    opacity: 1;
    transform: none;
    transition: none;
  }
}
.toc__link {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: baseline;
  gap: 1.5rem;
  text-decoration: none;
}
.toc__title {
  font-family: var(--display);
  font-size: clamp(1.35rem, 2.45vw, 1.9rem);
  font-weight: 450;
  letter-spacing: -0.012em;
  line-height: 1.18;
  /* Fraunces has these optional features; the variable axis SOFT relaxes
     the contrast, opsz adapts shape to size, ss01 enables the alternative
     g with the curled descender. Browsers without support quietly ignore. */
  font-variation-settings: "opsz" 96, "SOFT" 40;
  font-feature-settings: "kern" 1, "liga" 1, "dlig" 1, "ss01" 1;
  color: var(--ink);
  background-image: linear-gradient(var(--accent), var(--accent));
  background-size: 0% 1px;
  background-position: 0 100%;
  background-repeat: no-repeat;
  transition: background-size 0.45s cubic-bezier(0.2, 0.7, 0.3, 1);
  display: inline;
}
.toc__link:hover .toc__title { background-size: 100% 1px; }
.toc__leader { display: none; }
.toc__date {
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  color: var(--muted);
  white-space: nowrap;
}
.toc__summary {
  margin: 0.8rem 0 0;
  font-style: italic;
  color: var(--muted);
  font-size: 1rem;
}
.toc__tags { margin: 0.5rem 0 0; }
.tag {
  font-family: var(--mono);
  font-size: 0.66rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  padding-right: 0.9rem;
}
.tag::before {
  content: "·";
  padding-right: 0.35rem;
  color: var(--rule);
}
.toc__empty { color: var(--muted); padding: 1.2rem 0; }

.colophon {
  max-width: 36rem;
  margin: 4vh auto 8vh;
  padding: 0 var(--gut);
  font-style: italic;
  color: var(--muted);
  text-align: center;
  font-size: 0.95rem;
}

/* ───────── post page ───────── */
.post {
  max-width: 70rem;
  margin: 0 auto;
  padding: 0 var(--gut) 4vh;
}
.post__head {
  text-align: center;
  padding: 4vh 0 3vh;
}
.post__eyebrow {
  font-family: var(--mono);
  font-size: 0.68rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--muted);
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 0 auto 4rem;
  max-width: 56rem;
}
.post__eyebrow .back { text-decoration: none; }
.post__eyebrow .post__langs a {
  margin-left: 0.6rem;
  text-decoration: none;
}
.post__title {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(1.85rem, 4.6vw, 3.4rem);
  line-height: 1.08;
  letter-spacing: -0.005em;
  margin: 0 auto;
}
.post__summary {
  font-family: var(--serif);
  font-style: italic;
  color: var(--muted);
  font-size: clamp(1rem, 1.4vw, 1.2rem);
  line-height: 1.5;
  margin: 1.8rem auto 0;
}
.post__meta {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 1.8rem 0 0;
}
.post__meta .dot { padding: 0 0.45em; color: var(--rule); }
.post__hairline {
  width: 4rem;
  height: 1px;
  background: var(--accent);
  margin: 2.8rem auto 0;
}

/* ── post hero stagger ──
   The header doesn't have its own animation — it just lifts into place
   as the page renders. Each row fires slightly later than the one above
   it so the eye reads top-to-bottom. */
@keyframes postRise {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: none; }
}
.page-post .post__eyebrow { animation: postRise 0.7s cubic-bezier(0.2,0.7,0.3,1) 0.05s both; }
.page-post .post__title   { animation: postRise 0.85s cubic-bezier(0.2,0.7,0.3,1) 0.18s both; }
.page-post .post__summary { animation: postRise 0.85s cubic-bezier(0.2,0.7,0.3,1) 0.34s both; }
.page-post .post__meta    { animation: postRise 0.7s cubic-bezier(0.2,0.7,0.3,1) 0.5s both; }
.page-post .post__head .post__hairline {
  width: 0;
  animation: drawIn 1.4s cubic-bezier(0.2,0.7,0.3,1) 0.65s forwards;
}
.page-post .post__toc { animation: postRise 0.85s cubic-bezier(0.2,0.7,0.3,1) 0.78s both; }

/* ── post body scroll reveal ──
   JS marks `.post__body` with `.is-armed`. From there, h2/h3/pre/figure
   /display-math start translucent and lifted; the IntersectionObserver
   adds `.is-in` as each lands in view. Items already on screen at boot
   get `.is-in` immediately so nothing pops behind the reader. */
.post__body.is-armed > h2,
.post__body.is-armed > h3,
.post__body.is-armed > pre,
.post__body.is-armed > .code-block,
.post__body.is-armed > figure,
.post__body.is-armed > .katex-display,
.post__body.is-armed > blockquote {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 720ms cubic-bezier(0.2,0.7,0.3,1),
              transform 720ms cubic-bezier(0.2,0.7,0.3,1);
  will-change: opacity, transform;
}
.post__body.is-armed > .is-in {
  opacity: 1;
  transform: none;
}

/* hairline accent that sweeps under the active TOC entry */
.post__toc a.is-current {
  color: var(--ink);
  background-image: linear-gradient(var(--accent), var(--accent));
  background-repeat: no-repeat;
  background-position: 0 100%;
  background-size: 100% 1px;
}

@media (prefers-reduced-motion: reduce) {
  .page-post .post__eyebrow,
  .page-post .post__title,
  .page-post .post__summary,
  .page-post .post__meta,
  .page-post .post__toc {
    animation: none;
  }
  .page-post .post__head .post__hairline {
    animation: none;
    width: 4rem;
  }
  .post__body.is-armed > h2,
  .post__body.is-armed > h3,
  .post__body.is-armed > pre,
  .post__body.is-armed > .code-block,
  .post__body.is-armed > figure,
  .post__body.is-armed > .katex-display,
  .post__body.is-armed > blockquote {
    opacity: 1;
    transform: none;
    transition: none;
  }
}

/* in-post table of contents */
.post__toc {
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.04em;
  color: var(--muted);
  max-width: 38rem;
  margin: 3rem auto 0;
  padding: 0.8rem 1.5rem;
  border-left: 1px solid var(--rule);
}
.post__toc-h {
  text-transform: uppercase;
  letter-spacing: 0.25em;
  font-size: 0.62rem;
  margin: 0 0 0.8rem;
  color: var(--rule);
}
.post__toc ol { list-style: none; padding: 0; margin: 0; }
.post__toc li { margin: 0.3rem 0; }
.post__toc li.d2 { padding-left: 1.2rem; }
.post__toc a { color: var(--muted); text-decoration: none; }
.post__toc a:hover { color: var(--accent); }

.post__body {
  max-width: var(--col);
  margin: 4vh auto 0;
}
.post__body h1,
.post__body h2,
.post__body h3 {
  font-family: var(--serif);
  font-weight: 400;
  letter-spacing: 0.005em;
}
.post__body h1 { font-size: 1.55rem; margin: 3rem 0 1rem; }
.post__body h2 { font-size: 1.3rem;  margin: 2.4rem 0 0.9rem; }
.post__body h3 { font-size: 1.1rem;  margin: 1.8rem 0 0.6rem; }
.post__body h1::before,
.post__body h2::before {
  content: "";
  display: block;
  width: 1.4rem;
  height: 1px;
  background: var(--accent);
  margin-bottom: 0.6rem;
}
.post__body p { margin: 1rem 0; }
.post__body a.anchor {
  color: var(--rule);
  text-decoration: none;
  font-size: 0.7em;
  margin-right: 0.4em;
  opacity: 0;
  transition: opacity 0.2s ease, color 0.2s ease;
}
.post__body :is(h1, h2, h3):hover a.anchor { opacity: 1; }
.post__body a.anchor:hover { color: var(--accent); }

.post__body code {
  font-family: var(--mono);
  font-size: 0.86em;
  background: rgba(179, 74, 54, 0.08);
  padding: 0.05em 0.35em;
  border-radius: 2px;
  color: var(--accent);
}
.post__body pre,
.code-block pre {
  font-family: var(--mono);
  font-size: 0.84rem;
  line-height: 1.55;
  background: var(--paper-soft) !important;
  padding: 1.1rem 1.2rem;
  margin: 1.6rem -0.5rem;
  border-left: 2px solid var(--accent);
  overflow-x: auto;
}
.post__body pre code,
.code-block pre code {
  background: transparent;
  color: inherit;
  padding: 0;
}
.code-block { position: relative; }
.code-block::after {
  content: attr(data-lang);
  position: absolute;
  top: 0.7rem;
  right: 0.9rem;
  font-family: var(--mono);
  font-size: 0.6rem;
  color: var(--muted);
  letter-spacing: 0.22em;
  text-transform: uppercase;
  pointer-events: none;
}

/* ── collapsible long code blocks ──
   JS adds .is-collapsible (and initially .is-collapsed) when a block
   exceeds the threshold. Collapsed state caps the <pre> height via the
   custom property `--cb-collapsed-max` (set per-block from JS), then
   draws a fade gradient + a click-to-expand pill at the bottom. The
   gradient color matches the visible <pre> background, including
   under dark mode where the <pre> is filter-inverted. */
.code-block.is-collapsible { padding-bottom: 2.4rem; }
.code-block.is-collapsible.is-collapsed > pre {
  max-height: var(--cb-collapsed-max, 18em);
  overflow: hidden;
}
.code-block.is-collapsible.is-collapsed::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: 2.2rem;
  height: 6rem;
  background: linear-gradient(
    to bottom,
    color-mix(in srgb, var(--paper-soft) 0%, transparent),
    var(--paper-soft) 78%
  );
  pointer-events: none;
  z-index: 1;
  transition: opacity 320ms cubic-bezier(0.2, 0.7, 0.3, 1);
}
@media (prefers-color-scheme: dark) {
  /* the <pre> behind us is filter-inverted, so invert the overlay too
     to keep its color a visual match. */
  .code-block.is-collapsible.is-collapsed::before {
    filter: invert(0.92) hue-rotate(180deg);
  }
}
.code-block__toggle {
  position: absolute;
  left: 50%;
  bottom: 0.3rem;
  transform: translateX(-50%);
  font-family: var(--mono);
  font-size: 0.62rem;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--muted);
  background: var(--paper);
  border: 1px solid var(--rule);
  border-radius: 999px;
  padding: 0.4rem 1rem;
  cursor: pointer;
  z-index: 2;
  transition: color 220ms cubic-bezier(0.2, 0.7, 0.3, 1),
              border-color 220ms cubic-bezier(0.2, 0.7, 0.3, 1),
              transform 220ms cubic-bezier(0.2, 0.7, 0.3, 1);
}
.code-block__toggle:hover,
.code-block__toggle:focus-visible {
  color: var(--accent);
  border-color: var(--accent);
  outline: none;
  transform: translateX(-50%) translateY(-1px);
}
@media (prefers-reduced-motion: reduce) {
  .code-block.is-collapsible.is-collapsed::before { transition: none; }
  .code-block__toggle { transition: none; }
}

.math-display {
  margin: 1.8rem 0;
  overflow-x: auto;
  text-align: center;
}
.math-error {
  color: var(--accent);
  font-family: var(--mono);
  font-size: 0.85em;
  background: rgba(179, 74, 54, 0.08);
}

.figure {
  margin: 2.5rem auto;
  text-align: center;
}
.figure img {
  max-width: 100%;
  height: auto;
  border-radius: 1px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}
.figure figcaption {
  font-family: var(--serif);
  font-style: italic;
  font-size: 0.9rem;
  color: var(--muted);
  margin-top: 0.8rem;
}

blockquote {
  border-left: 2px solid var(--accent);
  margin: 1.5rem 0;
  padding-left: 1.2rem;
  color: var(--muted);
  font-style: italic;
}

ul, ol { padding-left: 1.4rem; }
ul li, ol li { margin: 0.35rem 0; }

.post__foot { margin-top: 6vh; text-align: center; }
.post__sig {
  font-family: var(--mono);
  font-size: 0.7rem;
  letter-spacing: 0.32em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 2rem 0 0;
}

/* ───────── footer ───────── */
.footer {
  max-width: 1100px;
  margin: 8vh auto 3rem;
  padding: 0 var(--gut);
  font-family: var(--mono);
  font-size: 0.66rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--muted);
}
.footer__rule {
  height: 1px;
  background: var(--rule);
  margin-bottom: 1rem;
}
.footer__row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.5rem;
}

/* ───────── reading progress (post page) ───────── */
.reading-progress {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: 2px;
  z-index: 100;
  pointer-events: none;
}
.reading-progress > span {
  display: block;
  height: 100%;
  background: linear-gradient(to right, var(--accent), var(--gold));
  transform-origin: left;
  transform: scaleX(0);
  transition: transform 0.08s linear;
}

/* pretext attaches `data-balanced="1"` once it has applied a max-width */
[data-pretext="balance"][data-balanced="1"] {
  transition: max-width 0.25s ease;
}

@media (max-width: 640px) {
  :root { --gut: 5vw; }
  .post__eyebrow { margin-bottom: 2.5rem; }
  .toc__link { grid-template-columns: 1fr; }
  .toc__date { margin-top: 0.4rem; }
}

/* ──────────────────────────────────────────────────────────────────
   Dark viz hero — the animated transformer
   Scoped token overrides so the rest of the page keeps warm paper.
   ────────────────────────────────────────────────────────────────── */

.hero--viz {
  /* self-contained palette — ignores prefers-color-scheme */
  --paper:      #0b0d12;
  --paper-soft: #14171f;
  --ink:        #ece6d3;
  --muted:      #7a8596;
  --rule:       #2a3142;
  --rule-soft:  #1b2030;
  --accent:     #5eead4;
  --accent-soft:#a78bfa;
  --gold:       #f59e0b;

  /* tviz-specific tokens (used by the SVG) */
  --tviz-fwd:    #5eead4;
  --tviz-fwd2:   #7dd3fc;
  --tviz-q:      #5eead4;
  --tviz-k:      #7dd3fc;
  --tviz-v:      #a78bfa;
  --tviz-bwd:    #ef4444;
  --tviz-bwd2:   #f59e0b;
  --tviz-rule:   #2a3142;
  --tviz-grid:   #1b2030;

  /* full-bleed */
  width: 100vw;
  margin-left: calc(50% - 50vw);
  margin-right: calc(50% - 50vw);
  max-width: none;

  background:
    radial-gradient(1200px 500px at 50% 5%, rgba(94, 234, 212, 0.06), transparent 70%),
    radial-gradient(900px 500px at 80% 110%, rgba(167, 139, 250, 0.06), transparent 70%),
    var(--paper);
  color: var(--ink);
  padding: 7vh var(--gut) 5.5vh;
  text-align: center;
  position: relative;
  isolation: isolate;
  border-bottom: 1px solid var(--rule-soft);
}
.hero--viz::before {
  /* thin top rule in the forward color */
  content: "";
  position: absolute;
  left: 0; right: 0; top: 0;
  height: 1px;
  background: linear-gradient(90deg,
    transparent, var(--tviz-fwd) 20%, var(--tviz-v) 50%, var(--tviz-bwd) 80%, transparent);
  opacity: 0.6;
}

.tviz {
  max-width: 1180px;
  margin: 0 auto;
  padding-bottom: 2.2rem;
}
.tviz__svg {
  display: block;
  width: 100%;
  height: auto;
  max-height: min(64vh, 560px);
  margin: 0 auto;
  overflow: visible;
  /* Decorative. Without this the browser hit-tests hundreds of SVG cells on
     every mousemove pixel, contending with the rAF animation. */
  pointer-events: none;
}
.tviz__caption {
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.18em;
  text-transform: lowercase;
  color: var(--muted);
  min-height: 1.6em;
  margin: 1.6rem auto 0;
  padding: 0 1rem;
  max-width: 58ch;
  transition: opacity 0.35s cubic-bezier(0.2, 0.7, 0.3, 1);
  pointer-events: none;
}
.tviz__scrub {
  list-style: none;
  display: flex;
  justify-content: center;
  gap: 0.45rem;
  padding: 0;
  margin: 1.2rem 0 0;
  pointer-events: none;
}
.tviz__dot {
  width: 14px;
  height: 2px;
  background: var(--rule);
  border-radius: 1px;
  transition: background 0.3s ease, width 0.3s ease, box-shadow 0.3s ease;
}
.tviz__dot.is-past     { background: color-mix(in oklab, var(--tviz-fwd) 40%, var(--rule)); }
.tviz__dot.is-past.is-bwd { background: color-mix(in oklab, var(--tviz-bwd) 40%, var(--rule)); }
.tviz__dot.is-current {
  width: 28px;
  background: var(--tviz-fwd);
  box-shadow: 0 0 10px color-mix(in oklab, var(--tviz-fwd) 60%, transparent);
}
.tviz__dot.is-current.is-bwd {
  background: var(--tviz-bwd);
  box-shadow: 0 0 10px color-mix(in oklab, var(--tviz-bwd) 60%, transparent);
}

/* ── identity block below the viz ── */
.hero__identity {
  margin: 1.8rem auto 0;
  max-width: 1100px;
}
.hero--viz .eyebrow { color: color-mix(in oklab, var(--tviz-fwd) 40%, var(--muted)); }
.hero--viz .hero__title {
  font-family: var(--display);
  font-weight: 460;
  color: var(--ink);
  letter-spacing: -0.015em;
  font-size: clamp(2.2rem, 6.8vw, 4.4rem);
  text-shadow: 0 0 24px color-mix(in oklab, var(--tviz-fwd) 20%, transparent);
  font-variation-settings: "opsz" 144, "SOFT" 50;
  font-feature-settings: "kern" 1, "liga" 1, "dlig" 1, "ss01" 1;
}
.hero--viz .hero__tagline {
  color: color-mix(in oklab, var(--ink) 65%, var(--muted));
}
.hero__tagline--rotating {
  transition: opacity 460ms cubic-bezier(0.2, 0.7, 0.3, 1),
              transform 460ms cubic-bezier(0.2, 0.7, 0.3, 1),
              max-width 460ms cubic-bezier(0.2, 0.7, 0.3, 1);
  will-change: opacity, transform;
}
.hero__tagline--rotating.is-fading {
  opacity: 0;
  transform: translateY(-4px);
}
.hero--viz .hero__hairline {
  background: linear-gradient(90deg, var(--tviz-fwd), var(--tviz-v));
}

/* ── tv-* internals: cells, connectors, labels ──
   Performance note: cell fill colors are precomputed in JS and set via the
   `fill` attribute at build time. Nothing in this section touches color-mix
   on the hot path — per-frame work is only opacity on overlay rects. */

.tv-mat__label {
  font-family: var(--mono);
  font-size: 11.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  fill: var(--muted);
}

.tv-cell__base {
  /* static — fill + stroke set via attributes in JS */
}
.tv-cell__fwd,
.tv-cell__bwd {
  will-change: opacity;
}
.tv-cell__val {
  font-family: var(--mono);
  font-size: 9.5px;
  letter-spacing: 0.01em;
  fill: var(--ink);
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum";
  pointer-events: none;
}

/* tokens */
.tv-token__bg {
  fill: var(--tviz-grid);
  stroke: var(--tviz-fwd);
  stroke-opacity: 0.45;
  stroke-width: 1;
}
.tv-token__bg--bwd {
  fill: #3a1a1a;
  stroke: var(--tviz-bwd);
  stroke-opacity: 0.7;
}
.tv-token__txt {
  font-family: var(--mono);
  font-size: 13px;
  letter-spacing: 0.22em;
  fill: var(--ink);
  text-transform: uppercase;
}

/* connectors */
.tv-conn {
  fill: none;
  stroke: var(--tviz-rule);
  stroke-width: 1.1;
  stroke-linecap: round;
  pointer-events: none;
}
.tv-conn--fwd {
  stroke: var(--tviz-fwd);
  stroke-opacity: 0.9;
  stroke-width: 1.5;
  filter: drop-shadow(0 0 3px rgba(94, 234, 212, 0.55));
}
.tv-conn--bwd {
  stroke: var(--tviz-bwd);
  stroke-opacity: 0.95;
  stroke-width: 1.5;
  filter: drop-shadow(0 0 3px rgba(239, 68, 68, 0.6));
}
.tv-conn--q { stroke: var(--tviz-q); filter: drop-shadow(0 0 3px rgba(94, 234, 212, 0.5)); }
.tv-conn--k { stroke: var(--tviz-k); filter: drop-shadow(0 0 3px rgba(125, 211, 252, 0.5)); }
.tv-conn--v { stroke: var(--tviz-v); filter: drop-shadow(0 0 3px rgba(167, 139, 250, 0.55)); }
.tv-conn--a { stroke: var(--tviz-fwd); filter: drop-shadow(0 0 3px rgba(94, 234, 212, 0.5)); }

/* leading-edge tip of a ray */
.tv-conn__tip {
  fill: #f5efe0;
  pointer-events: none;
  filter: drop-shadow(0 0 6px rgba(94, 234, 212, 0.95));
  will-change: opacity, cx, cy;
}
.tv-conn__tip--bwd {
  filter: drop-shadow(0 0 6px rgba(239, 68, 68, 0.95));
}

/* loss badge */
.tv-loss { pointer-events: none; }
.tv-loss__ring {
  fill: none;
  stroke: var(--tviz-bwd);
  stroke-width: 1.3;
  stroke-dasharray: 4 4;
}
.tv-loss__big {
  font-family: var(--serif);
  font-style: italic;
  font-size: 22px;
  fill: var(--tviz-bwd);
}
.tv-loss__sub {
  font-family: var(--mono);
  font-size: 9px;
  letter-spacing: 0.1em;
  fill: var(--muted);
}

/* depth silhouettes — suggest layer stack */
.tv-depth { pointer-events: none; }

/* ── floating math-glyph atmosphere ──
   Absolutely positioned spans inside .hero--viz, drifting on their own
   randomized animation timings. JS seeds each glyph's position, duration,
   and travel vector via CSS custom properties. */
.tv-glyphs {
  position: absolute;
  inset: 0;
  pointer-events: none;
  overflow: hidden;
  z-index: 0;
}
.tv-glyph {
  position: absolute;
  font-family: var(--mono);
  color: var(--tviz-fwd);
  white-space: nowrap;
  user-select: none;
  letter-spacing: 0.02em;
  opacity: 0;
  text-shadow: 0 0 8px rgba(94, 234, 212, 0.35);
  animation-name: tv-glyph-drift;
  animation-iteration-count: infinite;
  animation-timing-function: linear;
  will-change: transform, opacity;
}
.tv-glyph--sky    { color: var(--tviz-k); text-shadow: 0 0 8px rgba(125, 211, 252, 0.35); }
.tv-glyph--violet { color: var(--tviz-v); text-shadow: 0 0 8px rgba(167, 139, 250, 0.35); }

@keyframes tv-glyph-drift {
  0%   { transform: translate(0, 0); opacity: 0; }
  12%  { opacity: var(--tv-max-op, 0.1); }
  88%  { opacity: var(--tv-max-op, 0.1); }
  100% { transform: translate(var(--tv-dx, 0), var(--tv-dy, 0)); opacity: 0; }
}
@media (prefers-reduced-motion: reduce) {
  .tv-glyph { animation: none; opacity: 0.04; }
}

/* keep the active scene above the glyph backdrop */
.hero--viz .tviz,
.hero--viz .hero__identity {
  position: relative;
  z-index: 1;
}

/* ── training telemetry strip ──
   Mono dim line at the top of the hero. Values update ~7fps from JS,
   tied to the transformer's cycle counter so they feel coherent. */
.tv-telemetry {
  position: relative;
  z-index: 2;
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: baseline;
  gap: 0.45rem;
  font-family: var(--mono);
  font-size: 0.66rem;
  letter-spacing: 0.18em;
  text-transform: lowercase;
  color: color-mix(in oklab, var(--tviz-fwd) 35%, var(--muted));
  margin: 0 auto 1.6rem;
  padding: 0.35rem 0.9rem;
  pointer-events: none;
  max-width: 980px;
  font-variant-numeric: tabular-nums;
  font-feature-settings: "tnum";
}
.tv-telemetry [data-tele] {
  white-space: nowrap;
  transition: color 0.2s ease;
}
.tv-telemetry__dot { color: var(--tviz-rule); }
@media (max-width: 640px) {
  .tv-telemetry {
    font-size: 0.6rem;
    letter-spacing: 0.12em;
    gap: 0.3rem;
  }
}

/* ── reduced motion ── */
@media (prefers-reduced-motion: reduce) {
  .tviz__scrub { display: none; }
}

/* ── responsive tweaks ── */
@media (max-width: 780px) {
  .hero--viz {
    padding: 5vh var(--gut) 4vh;
  }
  .tviz__caption {
    font-size: 0.72rem;
    letter-spacing: 0.12em;
  }
  .tviz__svg {
    max-height: none;
  }
  .hero--viz .hero__title { font-size: clamp(1.8rem, 9vw, 2.8rem); }
}