/* A dark working sheet, coloured by a heat scale from deep red to pale amber. */
:root {
  color-scheme: dark;
  --ground: #140c10;
  --ground-soft: rgba(20, 12, 16, 0.84);
  --panel: #1d1217;
  --text: #f1e9e0;
  --muted: #b5a8a3;
  --rule: rgba(241, 233, 224, 0.16);
  --ember: #f08a4b;
  --hot: #ffd9a0;
  --deep: #8e1f2d;
  --display: "Newsreader", Georgia, serif;
  --body: "Geist", "Helvetica Neue", Arial, sans-serif;
  --mono: "JetBrains Mono", Menlo, monospace;
  --gutter: clamp(16px, 3.4vw, 56px);
}

:root:lang(ru) { --display: "Literata", Georgia, serif; }
:root:lang(zh-Hans) {
  --display: "Noto Serif SC", "Songti SC", serif;
  --body: "Geist", "Noto Sans SC", "PingFang SC", sans-serif;
  --mono: "JetBrains Mono", "Noto Sans SC", "PingFang SC", monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 72px; }
body {
  position: relative;
  margin: 0;
  overflow-x: hidden;
  background: var(--ground);
  color: var(--text);
  font: 400 16px/1.55 var(--body);
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; }
:focus-visible { outline: 2px solid var(--ember); outline-offset: 3px; }
h1, h2, h3 { margin: 0; font-weight: 400; text-wrap: balance; }
p { margin: 0; }
ul, ol { margin: 0; padding: 0; list-style: none; }
.label { color: var(--ember); font: 400 12px/1.4 var(--mono); }
main, .nav, .contact, .footer { position: relative; z-index: 1; }

/* Formula field */
.field { position: absolute; inset: 0; z-index: 0; overflow: hidden; pointer-events: none; }
.filters { position: absolute; }
.field-layer { position: absolute; inset: 0; color: var(--text); opacity: 0.24; }
.field-lantern {
  color: var(--hot);
  opacity: 0.8;
  -webkit-mask-image: radial-gradient(circle 240px at var(--mx, -999px) var(--my, -999px), #000 0%, transparent 100%);
  mask-image: radial-gradient(circle 240px at var(--mx, -999px) var(--my, -999px), #000 0%, transparent 100%);
}
.field-item { position: absolute; white-space: nowrap; font-size: 21px; transform-origin: left center; filter: url(#hand); } /* Filtered per formula: browsers limit how large a filtered area can be. */
.field-item small { margin-left: 14px; font: 500 15px "Caveat", cursive; }
/* Letters and digits switch to a handwriting face; symbols it lacks stay in KaTeX and rely on the wobble filter. */
.field-item .mathnormal, .field-item .mord:not(:has(*)), .field-item .text, .field-item .text .mord, .field-item .mop { font-family: "Caveat", cursive; font-style: normal; font-weight: 500; }
.field-item .katex .base > * { display: inline-block; }

/* Navigation */
.nav {
  position: sticky;
  top: 0;
  z-index: 5;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding-block: 12px;
  padding-inline: var(--gutter);
  border-bottom: 1px solid var(--rule);
  background: var(--ground-soft);
  backdrop-filter: blur(12px);
}
.wordmark { font: 400 23px/1 var(--display); text-decoration: none; }
.wordmark em { color: var(--ember); }
.nav nav { display: flex; align-items: center; gap: 24px; font-size: 14px; }
.nav nav a { text-decoration: none; }
.nav nav a:hover { color: var(--ember); }
.nav .nav-cta { padding: 5px 12px; border: 1px solid var(--rule); }

.nav-right { display: flex; flex-wrap: wrap; align-items: center; justify-content: flex-end; gap: 8px 24px; min-width: 0; }
.nav .langs { gap: 10px; padding-left: 20px; border-left: 1px solid var(--rule); color: var(--muted); font: 400 12px var(--mono); }
.nav .langs [aria-current] { color: var(--hot); }

/* Hero: copy and network share one sheet, with the network running to the page edge */
.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.05fr);
  gap: clamp(24px, 3vw, 48px);
  align-items: center;
  padding-block: 40px 28px;
  padding-left: var(--gutter);
}
.hero-copy { display: grid; gap: 20px; min-width: 0; padding: 16px; margin-left: -16px; background: var(--ground-soft); box-shadow: 0 0 26px 20px var(--ground-soft); }
h1 { font: 300 clamp(40px, 4.7vw, 72px)/1.02 var(--display); letter-spacing: -0.022em; }
h1 em { color: var(--hot); }
:lang(ru) h1 { font-size: clamp(36px, 4vw, 62px); line-height: 1.08; letter-spacing: -0.015em; }
:lang(zh-Hans) h1 { line-height: 1.2; letter-spacing: 0; }
:lang(zh-Hans) em { font-style: normal; white-space: nowrap; }
.subhead { max-width: 28em; font: 400 clamp(21px, 1.9vw, 27px)/1.25 var(--display); }
.lede { max-width: 35em; color: var(--muted); font-size: 18px; line-height: 1.5; }
.actions { display: flex; flex-wrap: wrap; align-items: center; gap: 20px; }
.button { padding: 11px 18px; background: var(--ember); color: var(--ground); font-weight: 500; text-decoration: none; transition: background 150ms ease; }
.button:hover { background: var(--hot); }
.text-link { text-underline-offset: 4px; }
.network { display: grid; gap: 6px; min-width: 0; margin: 0; }
.network canvas { display: block; width: 100%; height: clamp(320px, 42vw, 560px); background: radial-gradient(closest-side, var(--ground) 72%, transparent); }
.network figcaption { background: var(--ground-soft); display: flex; flex-wrap: wrap; justify-content: space-between; gap: 6px 20px; padding-right: var(--gutter); color: var(--muted); font: 400 11.5px/1.45 var(--mono); }
.network figcaption b { color: var(--text); font-weight: 500; }
.scale { display: inline-flex; align-items: center; gap: 8px; white-space: nowrap; }
.scale i { display: inline-block; width: 72px; height: 7px; background: linear-gradient(90deg, #5e1725, #c9392f, #f08a4b, #ffe7bd); }

/* Blocks run in a continuous two-column sheet: heading in the margin, content beside it */
.block {
  display: grid;
  grid-template-columns: minmax(180px, 0.27fr) minmax(0, 1fr);
  gap: clamp(20px, 3vw, 56px);
  padding-block: 32px;
  padding-inline: var(--gutter);
  border-top: 1px solid var(--rule);
}
.block-head { display: grid; align-content: start; gap: 8px; align-self: start; position: sticky; top: 72px; padding: 6px; margin: -6px; background: var(--ground-soft); box-shadow: 0 0 14px 10px var(--ground-soft); }
.block-head h2 { font: 300 30px/1.1 var(--display); letter-spacing: -0.01em; }
.block-head p { color: var(--muted); font-size: 14px; line-height: 1.45; }

/* Problems */
.problems { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 1px; background: var(--rule); border: 1px solid var(--rule); }
.problems li { display: grid; align-content: start; gap: 5px; min-width: 0; padding: 16px 18px; background: var(--panel); transition: background 150ms ease; }
.problems h3 { font: 400 23px/1.15 var(--display); }
.problems p { color: var(--muted); font-size: 14.5px; line-height: 1.45; }

/* Results ledger */
.ledger { background: var(--panel); border: 1px solid var(--rule); }
.ledger li {
  display: grid;
  grid-template-columns: 6.2rem minmax(0, 1fr) 9.5rem;
  gap: 20px;
  align-items: baseline;
  padding: 15px 18px;
  transition: background 150ms ease;
}
.ledger li + li { border-top: 1px solid var(--rule); }
.ledger li:hover { background: rgba(240, 138, 75, 0.07); }
.figure { color: var(--hot); font: 300 37px/1 var(--display); font-variant-numeric: lining-nums tabular-nums; }
.ledger h3 { margin-bottom: 3px; font: 500 16px/1.35 var(--body); }
.ledger p { max-width: 62ch; color: var(--muted); font-size: 14.5px; line-height: 1.5; }
.source { color: var(--ember); font: 400 12px/1.4 var(--mono); text-align: right; text-underline-offset: 3px; }
.source:hover { color: var(--hot); }

/* Services */
.services { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1px; background: var(--rule); border: 1px solid var(--rule); }
.services article { display: grid; grid-template-rows: auto 1fr auto; gap: 8px; min-width: 0; padding: 18px; background: var(--panel); }
.services h3 { font: 400 23px/1.15 var(--display); }
.services p { color: var(--muted); font-size: 14.5px; }
.tex { min-width: 0; overflow-x: auto; overflow-y: hidden; }
.services .tex { padding-top: 8px; color: var(--hot); font-size: 16px; }

/* Step cost model */
.model-grid { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 0.92fr); gap: 1px; background: var(--rule); border: 1px solid var(--rule); }
.stepper, .formulation { display: grid; align-content: start; gap: 12px; min-width: 0; padding: 18px; background: var(--panel); }
.stepper svg { display: block; width: 100%; height: auto; }
.stepper text { fill: var(--muted); font: 400 11px var(--mono); }
.dial { display: grid; grid-template-columns: auto minmax(0, 1fr) 2.4em; gap: 12px; align-items: center; color: var(--muted); font: 400 12px var(--mono); }
.dial input { width: 100%; min-width: 0; accent-color: var(--ember); }
.dial output { color: var(--text); text-align: right; font-variant-numeric: tabular-nums; }
.readout { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; margin: 0; }
.readout div { display: flex; flex-direction: column; justify-content: space-between; gap: 3px; }
.readout dt { color: var(--muted); font: 400 11px/1.3 var(--mono); }
.readout dd { margin: 0; color: var(--hot); font: 300 26px/1.1 var(--display); font-variant-numeric: lining-nums tabular-nums; }
.note { color: var(--muted); font: 400 11.5px var(--mono); }
.eq { display: grid; gap: 4px; padding-block: 12px; border-top: 1px solid var(--rule); }
.eq .tex { font-size: 15.5px; }
.eq span { color: var(--muted); font-size: 13.5px; }

/* Process */
.steps { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); border-block: 1px solid var(--rule); background: var(--ground-soft); counter-reset: step; }
.steps li { display: grid; align-content: start; gap: 5px; padding: 14px 16px 16px; counter-increment: step; }
.steps li + li { border-left: 1px solid var(--rule); }
.steps li::before { content: counter(step); color: var(--ember); font: 400 12px var(--mono); }
.steps h3 { font: 400 21px/1.15 var(--display); }
.steps p { color: var(--muted); font-size: 14px; line-height: 1.45; }

/* Papers */
.papers { background: var(--ground-soft); }
.papers li { display: grid; grid-template-columns: 3.4rem minmax(0, 1fr) 14rem; gap: 14px; align-items: baseline; padding-block: 8px; border-bottom: 1px solid var(--rule); font-size: 14.5px; line-height: 1.4; }
.papers li:first-child { padding-top: 0; }
.year, .by { color: var(--muted); font: 400 12px/1.4 var(--mono); }
.papers a { text-decoration: none; }
.papers a:hover { color: var(--ember); text-decoration: underline; text-underline-offset: 3px; }

/* Contact */
.contact {
  display: grid;
  grid-template-columns: minmax(0, 1.3fr) minmax(0, 0.7fr);
  gap: 32px;
  align-items: end;
  padding-block: 40px;
  padding-inline: var(--gutter);
  background: var(--ember);
  color: var(--ground);
}
.contact h2 { margin-bottom: 8px; font: 300 clamp(36px, 4.6vw, 64px)/1.03 var(--display); letter-spacing: -0.02em; }
.contact p { max-width: 36em; font-size: 16.5px; }
.contact-action { display: flex; flex-wrap: wrap; align-items: center; gap: 12px 16px; min-width: 0; }
.email { overflow-wrap: anywhere; font: 400 clamp(21px, 2vw, 28px)/1.15 var(--display); text-underline-offset: 5px; }
.copy { padding: 7px 12px; border: 1px solid var(--ground); background: transparent; color: var(--ground); font: 500 13px var(--body); cursor: pointer; }
.copy:hover { background: var(--ground); color: var(--ember); }
.footer { padding-block: 14px; padding-inline: var(--gutter); color: var(--muted); font: 400 12px var(--mono); }

@media (max-width: 1040px) {
  .hero { grid-template-columns: minmax(0, 1fr); padding-right: var(--gutter); }
  .network figcaption { padding-right: 0; }
  .network canvas { height: clamp(280px, 64vw, 480px); }
  .block { grid-template-columns: minmax(0, 1fr); }
  .block-head { position: static; }
  .model-grid { grid-template-columns: minmax(0, 1fr); }
  .problems { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 680px) {
  .nav .main-nav { display: none; }
  .nav .langs { padding-left: 0; border-left: 0; }
  .ledger li { grid-template-columns: minmax(0, 1fr); gap: 6px; padding: 14px; }
  .source { text-align: left; }
  .services, .problems { grid-template-columns: minmax(0, 1fr); }
  .steps { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .steps li:nth-child(3) { border-left: 0; }
  .steps li:nth-child(n+3) { border-top: 1px solid var(--rule); }
  .papers li { grid-template-columns: 3rem minmax(0, 1fr); }
  .papers .by { grid-column: 2; }
  .contact { grid-template-columns: minmax(0, 1fr); }
  .dial { grid-template-columns: minmax(0, 1fr) 2.4em; }
  .dial span { grid-column: 1 / -1; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .button, .ledger li { transition: none; }
}