/* ---------- theme ---------- */
:root{
  --font-sans:"Inter",ui-sans-serif,system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  --background:#fbfbfc;--foreground:#1b1c22;
  --card:#ffffff;--popover:#ffffff;
  --muted:#f1f2f5;--muted-foreground:#676b78;
  --border:#e3e5ea;--radius:10px;
  --primary:#1b1c22;--primary-foreground:#fafafa;
  --secondary:#f1f2f5;--secondary-foreground:#1b1c22;
  --accent:#5b5bd6;--accent-surface:#5b5bd612;--accent-surface-foreground:#1b1c22;
  --destructive:#e5484d;
  /* particle colours, shared by every diagram */
  --up:#e5484d;--dn:#3e8ef7;--el:#d4a106;--pos:#d6409f;--nu:#2f9e66;--w:#8e4ec6;--ph:#0aa2c0;--pr:#e5484d;--ne:#8b8d98;--gl:#9a9aa6;--al:#f76b15;
  --side-w:264px;--top-h:56px;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){
  :root:not([data-theme=light]){
    --background:#111217;--foreground:#ecedf1;--card:#191b22;--popover:#191b22;
    --muted:#20232b;--muted-foreground:#9a9fac;--border:#2b2f39;
    --primary:#ecedf1;--primary-foreground:#111217;--secondary:#242833;--secondary-foreground:#ecedf1;
    --accent:#8d8dff;--accent-surface:#8d8dff1c;--accent-surface-foreground:#ecedf1;
    color-scheme:dark;
  }
}
:root[data-theme=dark]{
  --background:#111217;--foreground:#ecedf1;--card:#191b22;--popover:#191b22;
  --muted:#20232b;--muted-foreground:#9a9fac;--border:#2b2f39;
  --primary:#ecedf1;--primary-foreground:#111217;--secondary:#242833;--secondary-foreground:#ecedf1;
  --accent:#8d8dff;--accent-surface:#8d8dff1c;--accent-surface-foreground:#ecedf1;
  color-scheme:dark;
}

/* ---------- base ---------- */
*,*::before,*::after{box-sizing:border-box}
html{scroll-padding-top:calc(var(--top-h) + 16px);-webkit-text-size-adjust:100%}
body{margin:0;background:var(--background);color:var(--foreground);font-family:var(--font-sans);font-size:16px;line-height:1.65;-webkit-font-smoothing:antialiased}
a{color:var(--accent);text-underline-offset:2px}
.skip{position:absolute;left:-999px;top:8px;background:var(--card);padding:6px 12px;border-radius:6px;z-index:100}
.skip:focus{left:8px}

/* ---------- top bar ---------- */
.topbar{position:sticky;top:0;z-index:30;height:var(--top-h);display:flex;align-items:center;gap:10px;padding:0 16px;
  background:color-mix(in srgb,var(--background) 86%,transparent);backdrop-filter:saturate(1.4) blur(10px);border-bottom:1px solid var(--border)}
.brand{display:flex;align-items:center;gap:10px;min-width:0;white-space:nowrap;overflow:hidden;font-weight:650;color:var(--foreground);text-decoration:none;letter-spacing:-.01em;font-size:15.5px}
.logo{width:22px;height:22px;position:relative;flex:none}
.logo::before,.logo::after{content:"";position:absolute;width:12px;height:12px;border-radius:50%}
.logo::before{left:1px;top:2px;background:var(--pr);box-shadow:9px 0 0 var(--ne)}
.logo::after{left:5px;top:9px;background:var(--pr);box-shadow:0 0 0 1.5px var(--background)}
.topbar .ibtn{font:inherit;width:36px;height:36px;display:grid;place-items:center;border-radius:8px;border:1px solid transparent;background:none;color:var(--foreground);cursor:pointer;font-size:18px;padding:0}
.topbar .ibtn:hover{background:var(--muted)}
.topbar .theme{margin-left:auto}
.topbar .menu{display:none}
.theme .moon{display:none}
:root[data-theme=dark] .theme .sun{display:none}:root[data-theme=dark] .theme .moon{display:inline}
@media (prefers-color-scheme:dark){:root:not([data-theme=light]) .theme .sun{display:none}:root:not([data-theme=light]) .theme .moon{display:inline}}

/* ---------- layout ---------- */
.layout{display:flex;min-height:calc(100vh - var(--top-h))}
.side{position:sticky;top:var(--top-h);align-self:flex-start;width:var(--side-w);flex:none;height:calc(100vh - var(--top-h));overflow-y:auto;
  padding:18px 12px 24px;border-right:1px solid var(--border);font-size:14.5px}
.side ol{list-style:none;margin:6px 0 0;padding:0}
.side a{display:flex;align-items:center;gap:10px;padding:7px 10px;border-radius:8px;color:var(--foreground);text-decoration:none;line-height:1.3}
.side a:hover{background:var(--muted)}
.side a.on{background:var(--accent-surface);color:var(--foreground);font-weight:600}
.side a.home{color:var(--muted-foreground);font-weight:500}
.side a.home.on{color:var(--foreground)}
.side-legend{margin:22px 10px 0;padding-top:16px;border-top:1px solid var(--border)}
.side-h{font-size:11.5px;letter-spacing:.07em;text-transform:uppercase;color:var(--muted-foreground);font-weight:600;margin-bottom:8px}
.side .legend{flex-direction:column;gap:5px;font-size:13px}
.scrim{display:none}

.sym{--c:var(--accent);display:inline-grid;place-items:center;flex:none;min-width:26px;height:26px;padding:0 4px;border-radius:7px;
  font-weight:700;font-size:13.5px;color:var(--c);background:color-mix(in srgb,var(--c) 14%,transparent);line-height:1}
.sym.big{min-width:40px;height:40px;font-size:19px;border-radius:10px}

.content{flex:1;min-width:0;max-width:820px;margin:0 auto;padding:40px 32px 64px}

/* ---------- chapter typography ---------- */
.eyebrow{display:flex;align-items:center;gap:10px;font-size:13px;font-weight:600;color:var(--muted-foreground);letter-spacing:.02em;margin-bottom:10px}
.content h1{font-size:34px;line-height:1.15;letter-spacing:-.022em;margin:0 0 12px;font-weight:720;text-wrap:balance}
.content .lede{color:var(--muted-foreground);font-size:17.5px;line-height:1.6;margin:0}
.content h2.sec{font-size:25px;letter-spacing:-.015em;line-height:1.25;margin:56px 0 10px;padding-top:28px;border-top:1px solid var(--border)}
.content h3{font-size:20px;letter-spacing:-.01em;line-height:1.3;margin:44px 0 8px}
.content p{margin:10px 0}
.content .body{margin-top:8px}
.content .body > svg,.content .body > div > svg{margin:10px 0}

.tldr{margin:28px 0 8px;padding:16px 20px 14px;border:1px solid var(--border);border-left:4px solid var(--accent);border-radius:var(--radius);background:var(--card)}
.tldr-h{font-size:12px;letter-spacing:.08em;text-transform:uppercase;font-weight:700;color:var(--accent);margin-bottom:6px}
.tldr ul{margin:0;padding-left:20px}
.tldr li{margin:5px 0;line-height:1.55}
.tldr li::marker{color:var(--muted-foreground)}

/* chapter chrome buttons: page styles define a bare `button{}` for the step-through controls */
.pager{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-top:64px;padding-top:24px;border-top:1px solid var(--border)}
.pager a{display:flex;flex-direction:column;gap:2px;padding:14px 16px;border:1px solid var(--border);border-radius:var(--radius);text-decoration:none;color:var(--foreground);font-weight:600;background:var(--card)}
.pager a:hover{border-color:var(--accent)}
.pager small{font-weight:500;color:var(--muted-foreground);font-size:12.5px}
.pager .nx{text-align:right;grid-column:2}

/* ---------- legend ---------- */
.legend{display:flex;flex-wrap:wrap;gap:8px 18px;font-size:14px}
.lg{display:inline-flex;align-items:center;gap:8px;white-space:nowrap}
.lg svg{display:inline-block;flex:none;height:14px;width:14px;overflow:visible}
.lg.dash svg,.lg.wave svg{width:22px}

/* ---------- home ---------- */
.hero{padding:20px 0 8px}
.hero h1{font-size:44px}
.cta{display:flex;gap:10px;flex-wrap:wrap;margin-top:24px}
.btn{display:inline-flex;align-items:center;padding:10px 18px;border-radius:9px;border:1px solid var(--border);background:var(--card);color:var(--foreground);text-decoration:none;font-weight:600;font-size:15px}
.btn:hover{border-color:var(--accent)}
.btn.pri{background:var(--primary);color:var(--primary-foreground);border-color:transparent}
.qgrid{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:12px;margin-top:14px}
.qcard{background:var(--card);border:1px solid var(--border);border-radius:var(--radius);padding:16px 18px;display:flex;flex-direction:column}
.qcard .qq{font-weight:700;font-size:16px;margin-bottom:4px}
.qcard p{font-size:14.5px;line-height:1.55;color:var(--muted-foreground);margin:4px 0 10px;flex:1}
.qcard p b{color:var(--foreground)}
.qcard a{font-size:13.5px;font-weight:600;text-decoration:none}
.drows{display:flex;flex-direction:column;gap:8px;margin-top:14px}
.drow{display:grid;grid-template-columns:40px 120px 1fr 96px 64px;align-items:center;gap:14px;padding:12px 16px;background:var(--card);border:1px solid var(--border);border-radius:var(--radius);color:var(--foreground);text-decoration:none}
.drow:hover{border-color:var(--accent)}
.drow .dn{font-weight:700}
.drow .dd{font-size:14.5px;line-height:1.5;color:var(--muted-foreground)}
.drow .dq,.drow .dz{display:flex;flex-direction:column;font-weight:600;font-size:14px;line-height:1.3}
.drow small{font-weight:500;font-size:11px;letter-spacing:.06em;text-transform:uppercase;color:var(--muted-foreground)}
.cgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:12px;margin-top:14px}
.ccard{display:grid;grid-template-columns:40px 1fr;column-gap:12px;row-gap:6px;padding:16px;background:var(--card);border:1px solid var(--border);border-radius:var(--radius);text-decoration:none;color:var(--foreground)}
.ccard:hover{border-color:var(--accent)}
.cc-t{display:flex;flex-direction:column;font-weight:700;line-height:1.3;align-self:center}
.cc-t small{font-weight:500;color:var(--muted-foreground);font-size:12px}
.cc-b{grid-column:1/-1;font-size:14px;line-height:1.5;color:var(--muted-foreground)}
.mut{color:var(--muted-foreground)}.sm{font-size:13.5px}

/* ---------- FAQ ---------- */
.qa{padding:4px 0 6px}
.qa + .qa{border-top:1px solid var(--border);margin-top:22px}
.qa h3{margin-top:26px!important}
.qa ul{padding-left:22px;margin:8px 0}.qa li{margin:5px 0}

/* ---------- responsive ---------- */
@media (max-width:900px){
  .topbar .menu{display:grid}
  .side{position:fixed;left:0;top:var(--top-h);z-index:25;background:var(--background);transform:translateX(-100%);transition:transform .25s ease;box-shadow:none}
  body.nav-open .side{transform:none;box-shadow:0 10px 40px rgba(0,0,0,.25)}
  body.nav-open .scrim{display:block;position:fixed;inset:var(--top-h) 0 0 0;z-index:20;background:rgba(0,0,0,.3)}
  .content{padding:28px 20px 48px}
  .content h1{font-size:28px}.hero h1{font-size:34px}
  .drow{grid-template-columns:40px 1fr auto;row-gap:4px}
  .drow .dd{grid-column:1/-1;grid-row:2}
  .drow .dq{display:none}
}
@media (max-width:520px){
  .brand{font-size:14px;min-width:0;white-space:nowrap}
  .pager{grid-template-columns:1fr}.pager .nx{grid-column:1}
  .stp .hd .ttl{flex-basis:100%}
}
@media (prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}.side{transition:none}}

/* no fade-in of hidden diagram parts on first paint */
html:not(.ready) [data-s],html:not(.ready) [data-tf]{transition:none!important}