/* ==========================================================================
   Siyuan Code — shared stylesheet
   A DNA-storage codec (Nature Communications). Promotional site.
   ========================================================================== */

/* ---------- design tokens ---------- */
:root{
  color-scheme: light;
  --paper:#f6f7f5;
  --surface:#ffffff;
  --surface-2:#eef1ef;
  --ink:#0d1b24;
  --ink-2:#3f515c;
  --muted:#6b7a84;
  --line:#e2e7e5;
  --line-strong:#cbd5d1;

  --brand:#0c8068;
  --brand-ink:#0a6a57;
  --brand-soft:#e0f0ea;
  --blue:#2a78d6;
  --amber:#b9850b;

  --nA:#2e9e5b; --nT:#d64545; --nC:#3b82c4; --nG:#e0a321;

  --shadow:0 1px 2px rgba(13,27,36,.05), 0 14px 34px -20px rgba(13,27,36,.20);
  --shadow-lg:0 2px 6px rgba(13,27,36,.06), 0 28px 60px -30px rgba(13,27,36,.30);
  --serif:"Source Serif 4", Georgia, "Times New Roman", serif;
  --sans:"Inter", system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono:ui-monospace, "SFMono-Regular", "JetBrains Mono", "Cascadia Code", Consolas, monospace;
  --maxw:1160px;
  --measure:66ch;
  --gutter:clamp(20px, 4vw, 40px);
  --radius:16px;
}
@media (prefers-color-scheme: dark){
  :root:where(:not([data-theme="light"])){
    color-scheme: dark;
    --paper:#0d0f11;
    --surface:#15191b;
    --surface-2:#1d2225;
    --ink:#eef2f1;
    --ink-2:#b8c2c4;
    --muted:#8b989e;
    --line:#272d30;
    --line-strong:#3b4448;
    --brand:#24b894;
    --brand-ink:#6fd6bc;
    --brand-soft:#102f28;
    --blue:#5b9be0;
    --amber:#e0b13c;
    --nA:#3ec47a; --nT:#e36868; --nC:#5a9fdf; --nG:#f0b93c;
    --shadow:0 1px 2px rgba(0,0,0,.4), 0 16px 40px -20px rgba(0,0,0,.7);
    --shadow-lg:0 2px 6px rgba(0,0,0,.5), 0 30px 70px -30px rgba(0,0,0,.85);
  }
}
:root[data-theme="dark"]{
  color-scheme: dark;
  --paper:#0d0f11;
  --surface:#15191b;
  --surface-2:#1d2225;
  --ink:#eef2f1;
  --ink-2:#b8c2c4;
  --muted:#8b989e;
  --line:#272d30;
  --line-strong:#3b4448;
  --brand:#24b894;
  --brand-ink:#6fd6bc;
  --brand-soft:#102f28;
  --blue:#5b9be0;
  --amber:#e0b13c;
  --nA:#3ec47a; --nT:#e36868; --nC:#5a9fdf; --nG:#f0b93c;
  --shadow:0 1px 2px rgba(0,0,0,.4), 0 16px 40px -20px rgba(0,0,0,.7);
  --shadow-lg:0 2px 6px rgba(0,0,0,.5), 0 30px 70px -30px rgba(0,0,0,.85);
}

/* ---------- reset / base ---------- */
*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  margin:0;font-family:var(--sans);font-size:16px;line-height:1.65;
  color:var(--ink);background:var(--paper);
  -webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility;
}
img,svg{max-width:100%;display:block}
a{color:var(--brand-ink);text-decoration-thickness:1px;text-underline-offset:3px}
a:hover{color:var(--brand)}
h1,h2,h3,h4{font-family:var(--serif);font-weight:600;line-height:1.12;margin:0;letter-spacing:-.015em}
p{margin:0}
strong{color:var(--ink)}
::selection{background:var(--brand-soft);color:var(--brand-ink)}
.skip{position:absolute;left:-9999px;top:0;background:var(--ink);color:var(--paper);padding:10px 16px;border-radius:0 0 8px 0;z-index:100;text-decoration:none}
.skip:focus{left:0}

.container{max-width:var(--maxw);margin:0 auto;padding:0 var(--gutter)}

/* bilingual show / hide */
html[data-lang="en"] [lang="zh"]{display:none}
html[data-lang="zh"] [lang="en"]{display:none}

/* ---------- nav ---------- */
.nav{position:sticky;top:0;z-index:50;background:color-mix(in srgb, var(--paper) 84%, transparent);backdrop-filter:blur(11px);-webkit-backdrop-filter:blur(11px);border-bottom:1px solid var(--line)}
.nav-inner{display:flex;align-items:center;justify-content:space-between;height:64px;gap:16px}
.wordmark{display:flex;align-items:center;gap:11px;font-weight:700;font-size:16.5px;letter-spacing:-.01em;color:var(--ink);text-decoration:none;white-space:nowrap}
.wordmark:hover{color:var(--ink)}
.wordmark .dot{width:30px;height:30px;border-radius:9px;flex:0 0 auto;background:linear-gradient(135deg,var(--brand),var(--blue));display:grid;place-items:center;color:#fff;font-family:var(--serif);font-weight:700;font-size:15px}
.wordmark small{font-weight:500;color:var(--muted);font-size:12.5px}
.parent-brand{display:inline-flex;align-items:center;font-size:13px;font-weight:600;color:var(--muted);text-decoration:none;margin-right:14px;white-space:nowrap}
.parent-brand:hover{color:var(--brand-ink)}
@media (max-width:960px){.wordmark small{display:none}}
.nav-links{display:flex;align-items:center;gap:22px}
.nav-links a{color:var(--ink-2);text-decoration:none;font-size:14px;font-weight:500}
.nav-links a:hover{color:var(--ink)}
.nav-tools{display:flex;align-items:center;gap:10px}
.lang-btn{
  cursor:pointer;font:inherit;font-size:13px;font-weight:600;color:var(--ink-2);
  background:var(--surface);border:1px solid var(--line-strong);border-radius:999px;padding:7px 13px;
}
.lang-btn:hover{color:var(--ink);border-color:var(--brand)}
.nav-cta{display:inline-flex;align-items:center;gap:7px;background:var(--ink);color:var(--paper)!important;padding:8px 16px;border-radius:999px;font-size:14px;font-weight:600;text-decoration:none}
.nav-cta:hover{background:var(--brand);color:#fff!important}

/* ---------- hero ---------- */
.hero{position:relative;overflow:hidden}
.hero::before{content:"";position:absolute;inset:0;background:radial-gradient(52% 62% at 78% 14%, var(--brand-soft) 0%, transparent 62%),radial-gradient(46% 55% at 10% 92%, color-mix(in srgb, var(--blue) 9%, transparent) 0%, transparent 60%);pointer-events:none}
.hero-inner{position:relative;display:grid;grid-template-columns:minmax(0,1.12fr) minmax(0,.88fr);gap:clamp(20px,5vw,60px);align-items:center;padding:clamp(52px,9vw,104px) 0 clamp(44px,7vw,84px)}
.eyebrow{display:inline-flex;align-items:center;gap:9px;font-size:12.5px;font-weight:600;letter-spacing:.06em;text-transform:uppercase;color:var(--brand-ink);background:var(--brand-soft);padding:7px 13px;border-radius:999px}
.eyebrow .tag{width:7px;height:7px;border-radius:50%;background:var(--brand)}
.hero h1{font-size:clamp(40px,6.6vw,78px);margin:20px 0 8px;font-weight:700;line-height:1.04}
.hero .subtitle{font-family:var(--serif);font-style:italic;font-size:clamp(18px,2.5vw,26px);color:var(--ink-2);font-weight:400}
.hero .lede{margin:16px 0 0;max-width:58ch;color:var(--ink-2);font-size:16.5px}
.hero-ctas{display:flex;flex-wrap:wrap;gap:12px;margin-top:26px}
.btn{display:inline-flex;align-items:center;gap:9px;text-decoration:none;padding:13px 22px;border-radius:12px;font-weight:600;font-size:15px;border:1px solid transparent;transition:transform .12s ease,background .12s ease,border-color .12s ease,color .12s ease;cursor:pointer}
.btn:hover{transform:translateY(-1px)}
.btn-primary{background:var(--ink);color:var(--paper)}
.btn-primary:hover{background:var(--brand);color:#fff}
.btn-ghost{background:transparent;color:var(--ink);border-color:var(--line-strong)}
.btn-ghost:hover{border-color:var(--brand);color:var(--brand)}
.btn .arr{transition:transform .12s ease}
.btn:hover .arr{transform:translate(1px,-1px)}
.hero-meta{display:flex;flex-wrap:wrap;gap:6px 18px;margin-top:24px;color:var(--muted);font-size:13.5px}
.hero-meta b{color:var(--ink);font-weight:600}
.hero-meta .lab{display:inline-flex;align-items:center;gap:6px}

.helix-wrap{position:relative;display:grid;place-items:center;min-height:300px}
.helix-wrap svg{width:min(100%,440px);height:auto;overflow:visible}
.hero-stat{position:absolute;left:0;bottom:4%;background:var(--surface);border:1px solid var(--line);border-radius:14px;box-shadow:var(--shadow);padding:13px 17px;min-width:150px}
.hero-stat .v{font-family:var(--sans);font-weight:800;font-size:30px;letter-spacing:-.03em;color:var(--ink);line-height:1}
.hero-stat .v .u{font-size:.5em;font-weight:700;color:var(--brand-ink)}
.hero-stat .k{font-size:11.5px;font-weight:600;letter-spacing:.05em;text-transform:uppercase;color:var(--muted);margin-top:5px}

/* ---------- stats band ---------- */
.stats{padding:clamp(40px,6vw,72px) 0}
.stats-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:14px}
.stat{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:22px 20px;box-shadow:var(--shadow)}
.stat .k{font-size:11.5px;font-weight:600;letter-spacing:.05em;text-transform:uppercase;color:var(--muted)}
.stat .v{font-family:var(--sans);font-weight:750;font-size:clamp(28px,3.8vw,38px);letter-spacing:-.03em;margin:7px 0 3px;color:var(--ink);line-height:1.05}
.stat .v em{font-style:normal}
.stat .v .u{font-size:.52em;font-weight:650;color:var(--brand-ink)}
.stat .s{font-size:13px;color:var(--ink-2)}
.compare-strip{margin-top:14px;background:linear-gradient(120deg,var(--brand-soft),color-mix(in srgb, var(--blue) 8%, var(--surface)));border:1px solid var(--line);border-radius:var(--radius);padding:18px 22px;display:flex;flex-wrap:wrap;gap:8px 30px;align-items:baseline}
.compare-strip .lead{font-weight:600;color:var(--ink);font-size:15px}
.compare-strip span{font-size:14px;color:var(--ink-2)}
.compare-strip b{color:var(--brand-ink);font-weight:700}

/* ---------- sections ---------- */
.section{padding:clamp(46px,6.5vw,84px) 0;border-top:1px solid var(--line)}
.kicker{font-size:12.5px;font-weight:600;letter-spacing:.09em;text-transform:uppercase;color:var(--brand-ink)}
.section h2{font-size:clamp(27px,4.2vw,42px);margin:12px 0 14px;font-weight:600}
.lead{color:var(--ink-2);font-size:17px;max-width:var(--measure)}
.section-head{max-width:var(--measure)}

/* ---------- cards ---------- */
.grid{display:grid;gap:16px;margin-top:30px}
.grid-3{grid-template-columns:repeat(3,1fr)}
.grid-2{grid-template-columns:repeat(2,1fr)}
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:26px 24px;box-shadow:var(--shadow)}
.card .ico{width:42px;height:42px;border-radius:12px;display:grid;place-items:center;margin-bottom:15px;background:var(--brand-soft);color:var(--brand-ink);font-weight:700;font-size:18px}
.card h3{font-size:20px;margin-bottom:8px}
.card p{color:var(--ink-2);font-size:15px}
.card .num{font-family:var(--serif);font-style:italic;color:var(--muted);font-size:14px;display:block;margin-bottom:7px}

/* story / narrative cards */
.story-card{position:relative;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:28px 26px;box-shadow:var(--shadow)}
.story-card h3{font-size:22px;margin-bottom:10px}
.story-card p{color:var(--ink-2);font-size:15.5px;max-width:var(--measure)}
.story-card .tagline{display:inline-block;font-family:var(--serif);font-style:italic;color:var(--brand-ink);font-size:16px;margin-top:14px}

.duo{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:30px}
.duo .pane{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:24px;box-shadow:var(--shadow)}
.duo .pane h3{font-size:19px;margin:12px 0 8px}
.duo .pane p{color:var(--ink-2);font-size:14.5px}
.duo .badge{display:inline-block;font-size:11.5px;font-weight:700;letter-spacing:.05em;text-transform:uppercase;padding:4px 10px;border-radius:999px}
.duo .badge.mech{background:color-mix(in srgb, var(--muted) 16%, transparent);color:var(--ink-2)}
.duo .badge.mol{background:var(--brand-soft);color:var(--brand-ink)}
.duo .ico{width:44px;height:44px;border-radius:12px;display:grid;place-items:center;font-size:21px}

/* callout */
.callout{margin-top:26px;padding:22px 26px;border-left:3px solid var(--brand);background:var(--surface);border-radius:0 var(--radius) var(--radius) 0;box-shadow:var(--shadow)}
.callout p{color:var(--ink-2);font-size:15.5px;max-width:74ch}
.callout strong{color:var(--ink)}

/* ---------- pipeline flow ---------- */
.flow-wrap{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);overflow:hidden;margin-top:30px}
.flow{display:grid;grid-template-columns:repeat(5,1fr);counter-reset:step}
.fstep{position:relative;padding:22px 18px 22px 22px}
.fstep::before{counter-increment:step;content:counter(step);position:absolute;top:20px;left:20px;width:26px;height:26px;border-radius:8px;background:var(--brand);color:#fff;display:grid;place-items:center;font-size:13px;font-weight:700;font-family:var(--sans)}
.fstep .t{font-weight:600;font-size:15px;color:var(--ink);margin:36px 0 6px}
.fstep p{font-size:13.5px;color:var(--ink-2)}
.fstep::after{content:"";position:absolute;top:27px;right:-9px;width:15px;height:15px;border-top:2px solid var(--line-strong);border-right:2px solid var(--line-strong);transform:rotate(45deg)}
.fstep:last-child::after{display:none}

/* ---------- results panels ---------- */
.panel{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:26px 24px;box-shadow:var(--shadow)}
.panel h3{font-size:21px;margin-bottom:6px}
.panel .sub{color:var(--muted);font-size:12px;font-weight:600;letter-spacing:.05em;text-transform:uppercase;margin-bottom:14px}
.panel p{color:var(--ink-2);font-size:15px}
.check{list-style:none;margin:16px 0 0;padding:0;display:grid;gap:9px}
.check li{position:relative;padding-left:26px;color:var(--ink-2);font-size:14.5px}
.check li::before{content:"✓";position:absolute;left:0;top:0;color:var(--brand-ink);font-weight:700}
.check b{color:var(--ink);font-weight:600}

/* ---------- figures ---------- */
.fig{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:16px;box-shadow:var(--shadow);margin-top:26px}
.fig img{width:100%;height:auto;border-radius:9px}
.fig figcaption{font-size:13px;color:var(--muted);margin-top:12px;line-height:1.5}
.fig figcaption b{color:var(--ink-2);font-weight:600}
.fig .fig-label{display:inline-block;font-family:var(--serif);font-weight:700;color:var(--brand-ink);margin-right:6px}
.math-body .fig-wide{max-width:none;width:min(calc(var(--maxw) - 2*var(--gutter)), calc(100vw - 2*var(--gutter)))}

/* ---------- comparison table + chart ---------- */
.table-wrap{overflow-x:auto;margin-top:26px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow)}
table.cmp{border-collapse:collapse;width:100%;min-width:720px;font-size:13.5px}
table.cmp th,table.cmp td{padding:11px 12px;text-align:center;border-bottom:1px solid var(--line);vertical-align:top}
table.cmp thead th{font-weight:600;font-size:12.5px;color:var(--ink-2);background:var(--surface-2);position:sticky;top:0}
table.cmp th.rowhead{text-align:left;font-weight:500;color:var(--muted);font-size:12.5px;width:150px}
table.cmp td.hi,table.cmp th.hi{background:var(--brand-soft);color:var(--brand-ink);font-weight:700}
table.cmp td.hi{color:var(--ink)}
table.cmp tbody tr:last-child td{border-bottom:none}

.chart{margin-top:26px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:26px 24px;box-shadow:var(--shadow)}
.chart h3{font-size:18px;margin-bottom:4px}
.chart .chart-sub{font-size:13px;color:var(--muted);margin-bottom:20px}
.chart-plot{position:relative}
.chart-row{display:grid;grid-template-columns:132px 1fr;gap:14px;align-items:center;margin-bottom:12px}
.chart-label{font-size:13px;color:var(--ink-2);text-align:right;line-height:1.2}
.chart-label .y{color:var(--muted);font-size:11.5px;display:block}
.chart-track{position:relative;height:26px;border-radius:6px}
.chart-track .bar{position:absolute;left:0;top:0;bottom:0;border-radius:6px;display:flex;align-items:center}
.chart-track .bar.gray{background:color-mix(in srgb, var(--muted) 26%, transparent)}
.chart-track .bar.accent{background:linear-gradient(90deg,var(--brand),color-mix(in srgb, var(--brand) 72%, var(--blue)))}
.chart-track .bar .val{position:absolute;right:-6px;top:50%;transform:translate(100%,-50%);font-size:13px;font-weight:600;color:var(--ink);font-variant-numeric:tabular-nums;white-space:nowrap}
.chart-gridlines{position:absolute;inset:0;pointer-events:none}
.chart-gridlines i{position:absolute;top:0;bottom:0;width:1px;background:var(--line)}
.chart-axis{display:flex;justify-content:space-between;font-size:11.5px;color:var(--muted);margin-top:8px;padding-left:146px;font-variant-numeric:tabular-nums}
.chart-note{font-size:12px;color:var(--muted);margin-top:14px}

/* ---------- author ---------- */
.author{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:28px 28px;box-shadow:var(--shadow);display:flex;gap:22px;align-items:flex-start;margin-top:16px}
.subhead{margin-top:34px;font-family:var(--sans);font-size:13px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--muted)}
.author .avatar{width:74px;height:74px;border-radius:50%;flex:0 0 auto;background:linear-gradient(135deg,var(--brand),var(--blue));display:grid;place-items:center;color:#fff;font-family:var(--serif);font-weight:700;font-size:26px}
.author h3{font-size:21px}
.author h3 a{color:var(--ink);text-decoration:none}
.author h3 a:hover{color:var(--brand-ink)}
.author .role{font-size:12.5px;font-weight:600;letter-spacing:.05em;text-transform:uppercase;color:var(--brand-ink);margin:2px 0 10px}
.author p{color:var(--ink-2);font-size:14.5px;max-width:var(--measure)}
.author .creds{margin-top:10px;display:flex;flex-wrap:wrap;gap:6px}
.author .creds span{font-size:12px;color:var(--ink-2);background:var(--surface-2);border:1px solid var(--line);border-radius:999px;padding:4px 11px}

/* ---------- availability ---------- */
.links{display:grid;grid-template-columns:repeat(2,1fr);gap:14px;margin-top:30px}
.link{display:flex;align-items:center;gap:14px;background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:18px 18px;text-decoration:none;box-shadow:var(--shadow);transition:border-color .12s ease,transform .12s ease}
.link:hover{border-color:var(--brand);transform:translateY(-1px)}
.link .li{width:38px;height:38px;border-radius:10px;flex:0 0 auto;background:var(--brand-soft);color:var(--brand-ink);display:grid;place-items:center;font-weight:700;font-size:15px}
.link .lt{font-weight:600;font-size:15px;color:var(--ink)}
.link .ls{font-size:12.5px;color:var(--muted);font-family:var(--mono)}

/* ---------- citation ---------- */
.cite{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:24px 26px;box-shadow:var(--shadow);margin-top:26px;position:relative}
.cite pre{margin:0;font-family:var(--serif);font-size:15.5px;line-height:1.6;color:var(--ink);white-space:pre-wrap;word-break:break-word}
.cite .copy{position:absolute;top:14px;right:14px;cursor:pointer;font:inherit;font-size:12.5px;font-weight:600;color:var(--ink-2);background:var(--surface-2);border:1px solid var(--line-strong);border-radius:8px;padding:6px 11px}
.cite .copy:hover{color:var(--ink);border-color:var(--brand)}

/* ---------- math pages (theory / derivation) ---------- */
.math-shell{padding:clamp(40px,6vw,72px) 0 clamp(56px,8vw,96px)}
.math-head{border-bottom:1px solid var(--line);padding-bottom:22px;margin-bottom:8px}
.math-head .crumb{font-size:13px;color:var(--muted);margin-bottom:8px}
.math-head .crumb a{color:var(--brand-ink);text-decoration:none}
.math-head h1{font-size:clamp(30px,4.6vw,46px);margin:6px 0 10px}
.math-body{max-width:var(--measure)}
.math-body h2{font-size:clamp(22px,3vw,30px);margin:44px 0 12px;padding-top:6px}
.math-body h3{font-size:19px;margin:30px 0 10px}
.math-body p{color:var(--ink-2);font-size:16px;margin:0 0 16px;max-width:var(--measure)}
.math-body ul,.math-body ol{margin:0 0 18px;padding-left:22px;color:var(--ink-2)}
.math-body li{margin-bottom:7px}
.math-body .lead{color:var(--ink-2)}

.toc{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:20px 24px;box-shadow:var(--shadow);margin-top:26px;max-width:var(--measure)}
.toc h4{font-family:var(--sans);font-size:12px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);margin-bottom:10px}
.toc ul{margin:0;padding:0;list-style:none;display:grid;gap:5px}
.toc a{font-size:14px;text-decoration:none}

.thm,.lem,.def,.cor{background:var(--surface);border:1px solid var(--line);border-left:3px solid var(--brand);border-radius:0 var(--radius) var(--radius) 0;padding:18px 22px;margin:22px 0;box-shadow:var(--shadow);max-width:var(--measure)}
.thm .tag,.lem .tag,.def .tag,.cor .tag{font-family:var(--sans);font-size:11.5px;font-weight:700;letter-spacing:.07em;text-transform:uppercase;color:var(--brand-ink);display:block;margin-bottom:8px}
.thm .body,.lem .body,.def .body,.cor .body{font-size:15.5px;color:var(--ink)}
.thm .body em,.lem .body em{color:var(--ink)}
.proof{margin:0 0 20px;padding:14px 18px;border-left:1px dashed var(--line-strong);color:var(--ink-2);font-size:14.5px;max-width:var(--measure)}
.proof .tag{font-family:var(--sans);font-weight:700;font-style:normal;color:var(--muted);font-size:12px;letter-spacing:.06em;text-transform:uppercase;margin-right:6px}

.algo{background:var(--surface-2);border:1px solid var(--line);border-radius:12px;padding:18px 20px;margin:20px 0;font-family:var(--mono);font-size:13px;line-height:1.7;color:var(--ink);overflow-x:auto;max-width:var(--measure)}
.algo .cap{font-family:var(--sans);font-size:12px;font-weight:600;color:var(--muted);margin-bottom:10px}
.algo .cm{color:var(--muted);font-style:italic}

/* KaTeX sizing */
.math-body .katex{font-size:1.04em}
.math-body .katex-display{margin:18px 0;overflow-x:auto;overflow-y:hidden;padding:2px 0}
.math-body .katex-display>.katex{white-space:normal}

/* ---------- footer ---------- */
.footer{border-top:1px solid var(--line);padding:46px 0 64px;background:var(--surface-2)}
.footer .container{display:flex;flex-wrap:wrap;gap:24px 48px;justify-content:space-between;align-items:flex-start}
.footer .brand{max-width:46ch}
.footer p{color:var(--muted);font-size:13.5px;max-width:62ch}
.footer .col h4{font-family:var(--sans);font-size:12.5px;font-weight:700;letter-spacing:.05em;text-transform:uppercase;color:var(--ink-2);margin-bottom:10px}
.footer .col a{display:block;color:var(--muted);text-decoration:none;font-size:13.5px;margin-bottom:7px}
.footer .col a:hover{color:var(--brand-ink)}

/* ---------- reveal ---------- */
.rv{opacity:0;transform:translateY(15px);transition:opacity .55s ease,transform .55s ease}
.rv.in{opacity:1;transform:none}
@media (prefers-reduced-motion: reduce){
  html{scroll-behavior:auto}
  .rv{opacity:1;transform:none;transition:none}
}

/* ---------- responsive ---------- */
@media (max-width:960px){
  .hero-inner{grid-template-columns:1fr}
  .helix-wrap{order:-1;min-height:200px;margin-bottom:-16px}
  .hero-stat{bottom:0}
  .stats-grid{grid-template-columns:repeat(2,1fr)}
  .grid-3,.grid-2,.duo,.links{grid-template-columns:1fr}
  .flow{grid-template-columns:1fr}
  .fstep::after{display:none}
  .fstep .t{margin-top:6px}
  .fstep{padding-left:56px}
  .fstep::before{top:16px;left:16px}
  .chart-row{grid-template-columns:104px 1fr}
  .chart-axis{padding-left:118px}
  .nav-links{display:none}
}
@media (max-width:480px){
  .stats-grid{grid-template-columns:1fr}
  .author{flex-direction:column}
}