/* Bolyai-triunghi: chalk and ink in a geometer's notebook. */
@font-face{font-family:"Newsreader";font-style:normal;font-weight:400 700;font-display:swap;
  src:url("fonts/newsreader-latin.woff2?v=725d78a558") format("woff2");unicode-range:U+0000-00FF,U+2013-2014,U+2018-201D,U+201E,U+2212;}
@font-face{font-family:"Newsreader";font-style:normal;font-weight:400 700;font-display:swap;
  src:url("fonts/newsreader-latin-ext.woff2?v=aed527cdc1") format("woff2");unicode-range:U+0100-024F,U+1E00-1EFF,U+20AC;}
@font-face{font-family:"Atkinson";font-style:normal;font-weight:400 700;font-display:swap;
  src:url("fonts/atkinson-latin.woff2?v=18b2a1a39a") format("woff2");unicode-range:U+0000-00FF,U+2013-2014,U+2018-201D,U+201E,U+2212;}
@font-face{font-family:"Atkinson";font-style:normal;font-weight:400 700;font-display:swap;
  src:url("fonts/atkinson-latin-ext.woff2?v=7dae0c6c66") format("woff2");unicode-range:U+0100-024F,U+1E00-1EFF;}
@font-face{font-family:"PlexMono";font-style:normal;font-weight:400 600;font-display:swap;
  src:url("fonts/plexmono-latin.woff2?v=08949f728d") format("woff2");unicode-range:U+0000-00FF,U+2013-2014,U+2018-201D,U+201E,U+2212;}
@font-face{font-family:"PlexMono";font-style:normal;font-weight:400 600;font-display:swap;
  src:url("fonts/plexmono-latin-ext.woff2?v=6bc0f226a5") format("woff2");unicode-range:U+0100-024F;}
:root{
  --paper:#f5f0e3;--surface:#ece3cf;--card:#fffdf4;--ink:#20242c;--ink-2:#565b66;
  --line-soft:#d6cbb0;--brass:#7a5410;--brass-ink:#7a5410;
  --stage:#111927;--sea:#172535;--land:#31465c;--land-edge:#4c6379;
  --chalk:#f5f1e6;--hud-bg:rgba(13,19,30,.9);--hud-ink:#f5f1e6;
  --serif:"Newsreader",Georgia,serif;--sans:"Atkinson",system-ui,sans-serif;
  --mono:"PlexMono",ui-monospace,monospace;
}
:root[data-theme="dark"]{
  --paper:#0e141d;--surface:#161e2a;--card:#141b27;--ink:#e9e6dc;--ink-2:#a9afbb;
  --line-soft:#2b3648;--brass:#f2c35b;--brass-ink:#f2c35b;
  --stage:#0b1119;--sea:#13202e;--land:#2b4056;--land-edge:#46586e;
  --chalk:#f5f1e6;--hud-bg:rgba(9,13,20,.92);--hud-ink:#f5f1e6;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --paper:#0e141d;--surface:#161e2a;--card:#141b27;--ink:#e9e6dc;--ink-2:#a9afbb;
  --line-soft:#2b3648;--brass:#f2c35b;--brass-ink:#f2c35b;
  --stage:#0b1119;--sea:#13202e;--land:#2b4056;--land-edge:#46586e;
  --chalk:#f5f1e6;--hud-bg:rgba(9,13,20,.92);--hud-ink:#f5f1e6;}}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
section[id]{scroll-margin-top:3.75rem}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--serif);
  font-size:1.125rem;line-height:1.65;-webkit-font-smoothing:antialiased}
.wrap{max-width:66ch;margin:0 auto;padding:0 1.25rem}
.wrap-wide{max-width:72rem;margin:0 auto;padding:0 1.25rem}
.sr-status{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.skip{position:absolute;left:.5rem;top:-3rem;background:var(--ink);color:var(--paper);padding:.5rem 1rem;z-index:99}
.skip:focus{top:.5rem}
/* topbar */
.topbar{position:sticky;top:0;z-index:50;display:flex;align-items:center;gap:.75rem;
  height:3rem;padding:0 .9rem;background:var(--paper);border-bottom:1px solid var(--line-soft)}
.topbar .home{display:flex;align-items:center;gap:.45rem;color:var(--ink);text-decoration:none;
  font-family:var(--sans);font-size:.95rem}
.topbar .home svg{width:1.1rem;height:1.1rem;color:var(--brass)}
.topnav{display:flex;gap:.15rem;overflow-x:auto;font-family:var(--sans);font-size:.85rem}
.topnav a{color:var(--ink-2);text-decoration:none;padding:.3rem .5rem;white-space:nowrap}
.topnav a:hover{color:var(--brass-ink)}
.mobile-nav{display:none;font-family:var(--sans);font-size:.9rem}
.spacer{flex:1}
.chip{font-family:var(--sans);font-size:.85rem;color:var(--ink);text-decoration:none;
  border:1px solid var(--line-soft);border-radius:999px;padding:.2rem .7rem}
.icon-btn{background:none;border:1px solid var(--line-soft);border-radius:999px;color:var(--ink);
  width:2.2rem;height:2.2rem;display:inline-flex;align-items:center;justify-content:center;cursor:pointer}
/* progress */
.progress{position:sticky;top:3rem;z-index:49;height:3px;background:transparent}
.progress i{display:block;height:100%;width:100%;background:var(--line-soft);transform-origin:0 50%;transform:scaleX(0)}
.progress #pstamp{position:absolute;top:-9px;left:0;width:1.1rem;height:1.1rem;color:var(--brass)}
.progress #pstamp svg{width:100%;height:100%}
/* rail */
.rail{display:none}
@media(min-width:80rem){.rail{display:flex;flex-direction:column;gap:.55rem;position:fixed;right:1.1rem;top:30vh;z-index:40}}
.rail a{width:.7rem;height:.7rem;border-radius:50%;background:var(--line-soft);position:relative}
.rail a[aria-current="true"]{background:var(--brass)}
.rail a span{position:absolute;right:1.2rem;top:50%;transform:translateY(-50%);white-space:nowrap;
  font-family:var(--sans);font-size:.8rem;background:var(--surface);color:var(--ink);
  padding:.1rem .5rem;border-radius:.4rem;border:1px solid var(--line-soft);display:none}
.rail a:hover span,.rail a:focus-visible span{display:block}
/* hero: the hall, full-bleed, with the question over it */
.hero{position:relative;display:grid;grid-template-rows:1fr auto auto;min-height:min(96svh,60rem);margin:0}
.hero img{position:absolute;inset:0;width:100%;height:100%;object-fit:cover;display:block}
.hero .scrim{position:absolute;inset:0;
  background:linear-gradient(180deg,rgba(8,11,17,.28) 0%,rgba(8,11,17,.06) 34%,rgba(8,11,17,.78) 78%,rgba(8,11,17,.92) 100%)}
.hero-fig{position:relative;z-index:1;grid-row:1;align-self:end;justify-self:center;margin:3.2rem 0 0;width:min(92vw,22rem);color:#f7f3e8;text-align:center}
.hero-fig svg{display:block;width:100%;height:auto;max-height:30svh}
.hero-fig figcaption{font-family:var(--sans);font-size:.95rem;text-shadow:0 1px 6px rgba(0,0,0,.8);margin-top:.2rem}
.hero-text{position:relative;z-index:1;grid-row:2;max-width:66ch;margin:0 auto;
  padding:2rem 1.25rem 1.2rem;width:100%;color:#f7f3e8}
.hero-text h1{font-size:clamp(1.85rem,4.6vw,3rem);line-height:1.1;margin:.2rem 0 1rem;max-width:24ch;
  text-shadow:0 2px 14px rgba(0,0,0,.75)}
.hero-text .deck{font-size:1.2rem;line-height:1.55;margin:0 0 1.2rem;max-width:54ch;
  text-shadow:0 1px 8px rgba(0,0,0,.8)}
.hero-text .deck b{color:#f2c35b;font-weight:600}
.picker{display:flex;flex-wrap:wrap;align-items:center;gap:.6rem .8rem;
  background:rgba(10,14,21,.62);border:1px solid rgba(245,241,230,.28);border-radius:.7rem;
  padding:.8rem .9rem;backdrop-filter:blur(3px)}
.picker label{font-family:var(--sans);font-size:.92rem}
.picker select{font-family:var(--sans);font-size:1rem;min-height:44px;max-width:100%;
  background:#f7f3e8;color:#1c2029;border:1px solid #f7f3e8;border-radius:.45rem;padding:.45rem .6rem}
.picker .btn{min-height:44px}
.hero-links{display:flex;flex-wrap:wrap;gap:.4rem 1.2rem;margin:.9rem 0 0;font-family:var(--sans);font-size:.95rem}
.hero-links a{color:#f2c35b;text-shadow:0 1px 6px rgba(0,0,0,.8)}
.hero-text .near{font-family:var(--sans);font-size:.9rem;margin:.7rem 0 0;color:rgba(247,243,232,.85);text-shadow:0 1px 6px rgba(0,0,0,.8)}
.hero-cap{position:relative;z-index:1;grid-row:3;max-width:66ch;margin:0 auto;width:100%;padding:0 1.25rem 1.4rem;
  font-family:var(--sans);font-size:.8rem;color:rgba(247,243,232,.85)}
.hero-cap a{color:inherit}
.btn{font-family:var(--sans);font-size:.95rem;padding:.6rem 1.1rem;min-height:44px;border-radius:.45rem;
  border:1px solid var(--line-soft);background:var(--surface);color:var(--ink);cursor:pointer}
.btn.primary{background:var(--brass);border-color:var(--brass);color:#fff}
:root[data-theme="dark"] .btn.primary{color:#14100a}
.hint{text-align:center;font-family:var(--sans);color:var(--ink-2);margin:1.2rem 0 2rem}
/* scrolly + stage */
.scrolly{position:relative}
.stage{position:sticky;top:3.2rem;height:100lvh;max-height:100lvh;background:var(--stage);
  overflow:hidden;border-top:1px solid var(--line-soft);border-bottom:1px solid var(--line-soft)}
.stage canvas{position:absolute;inset:0;width:100%;height:100%;display:block}
.hud{position:absolute;left:0;right:0;top:0;padding:.7rem 1rem .8rem;background:var(--hud-bg);color:var(--hud-ink);
  font-family:var(--sans);font-size:.95rem;border-bottom:1px solid rgba(245,241,230,.14)}
.hud .hud-line{margin:0}
.hud .hud-line b{color:#f2c35b;font-weight:600}
.hud .hud-sub{display:flex;justify-content:space-between;gap:1rem;margin:.25rem 0 0;font-size:.8rem;
  color:rgba(245,241,230,.78)}
.hud .hud-sub .agree{color:#9fe6a8}
.vlabels{position:absolute;inset:0;pointer-events:none}
.vlab{position:absolute;transform:translate(-50%,-130%);font-family:var(--sans);font-size:.85rem;
  color:var(--chalk);background:rgba(10,14,21,.72);border:1px solid rgba(245,241,230,.25);
  border-radius:.4rem;padding:.15rem .5rem;white-space:nowrap;pointer-events:auto;cursor:pointer}
.vlab small{color:#f2c35b;font-family:var(--mono);font-size:.72rem}
.vlab[hidden]{display:none}
.beat-chip{position:absolute;right:.8rem;bottom:.8rem;font-family:var(--mono);font-size:.78rem;
  color:rgba(245,241,230,.85);background:rgba(10,14,21,.66);border:1px solid rgba(245,241,230,.2);
  border-radius:.4rem;padding:.2rem .55rem}
.scalebar{position:absolute;left:1rem;bottom:.9rem;font-family:var(--mono);font-size:.75rem;color:var(--chalk)}
.scalebar i{display:block;height:3px;background:var(--chalk);margin-bottom:.15rem}
.step{min-height:72vh;display:flex;flex-direction:column;justify-content:center;padding:1.5rem 0}
.step .card{background:var(--card);border:1px solid var(--line-soft);border-radius:.7rem;padding:1.1rem 1.2rem}
.step .yr-tag{font-family:var(--mono);font-size:.82rem;color:var(--brass-ink);margin:0 0 .3rem}
.step h3{font-size:1.35rem;margin:.2rem 0 .5rem;line-height:1.25}
.step p{margin:.3rem 0}
.step p b{color:var(--brass-ink)}
.steps{padding:2rem 0}
#scara{padding-left:1.25rem;padding-right:1.25rem}
.stage-fallback{display:none}
/* paper sections */
.paper{padding:0 0 1rem}
.block{padding:2.5rem 0;border-top:1px solid var(--line-soft)}
.block h2{font-size:1.7rem;margin:0 0 .8rem;line-height:1.2}
.block h2 .anchor{color:inherit;text-decoration:none}
.block h3{font-size:1.25rem;margin:1.8rem 0 .5rem}
.lede{color:var(--ink-2)}
.fig{margin:2rem auto;max-width:60rem}
.fig img{width:100%;height:auto;display:block;border-radius:.4rem}
.fig figcaption{font-family:var(--sans);font-size:.85rem;color:var(--ink-2);margin-top:.5rem}
.wide-fig{max-width:60rem}
.table-scroll{display:block;width:100%;min-width:0;max-width:100%;overflow-x:auto;overscroll-behavior-inline:contain}
.table-scroll:focus-visible{outline:2px solid var(--brass-ink);outline-offset:2px}
table.ledger,table.prag{border-collapse:collapse;width:100%;margin:1.2rem 0;font-family:var(--sans);font-size:.92rem}
table.ledger caption,table.prag caption{text-align:left;font-family:var(--sans);font-size:.85rem;
  color:var(--ink-2);margin-bottom:.4rem}
table.ledger th,table.ledger td,table.prag th,table.prag td{border:1px solid var(--line-soft);
  padding:.45rem .6rem;text-align:left;vertical-align:top}
table.ledger thead th,table.prag thead th{background:var(--surface)}
table.ledger td.num,table.prag td.num{font-family:var(--mono);font-size:.82rem;white-space:nowrap}
.figsvg{width:100%;height:auto;display:block}
.figsvg text{font-family:var(--sans)}
.figsvg .t-panel{font-size:22px;font-weight:700;fill:var(--ink)}
.figsvg .t-sum{font-family:var(--mono);font-size:26px;fill:var(--brass-ink)}
.figsvg .t-note{font-size:16px;fill:var(--ink-2)}
.figsvg .tri-edge{stroke:var(--brass-ink);stroke-width:3;fill:none}
.figsvg .tri-fill{fill:var(--surface);stroke:var(--line-soft)}
details.what{margin:1.2rem 0;border:1px solid var(--line-soft);border-radius:.5rem;padding:.7rem 1rem}
details.what summary{font-family:var(--sans);cursor:pointer;min-height:44px}
/* instrument */
.tri-grid{display:grid;gap:.8rem;margin:1.2rem 0}
.tri-grid label{font-family:var(--sans);font-size:.9rem;display:grid;gap:.3rem}
.tri-grid select{font-family:var(--sans);font-size:1rem;min-height:44px;background:var(--card);
  color:var(--ink);border:1px solid var(--line-soft);border-radius:.45rem;padding:.45rem .6rem;max-width:100%}
.t-ans{font-size:1.15rem;border-left:4px solid var(--brass);padding:.4rem 0 .4rem .9rem;margin:1rem 0}
.method-note{font-size:.95rem;color:var(--ink-2)}
.privacy{font-family:var(--sans);font-size:.9rem;color:var(--ink-2)}
.share{--sr-acc:var(--brass-ink)}
ol.method{padding-left:1.3rem}
.method li{margin:.55rem 0}
.src-h{font-size:1.05rem;margin:1.4rem 0 .3rem}
.srcs{margin:.2rem 0 1rem;padding-left:1.2rem;font-size:.95rem}
.srcs li{margin:.3rem 0}
.srcs a{color:var(--brass-ink)}
.see-also{font-family:var(--sans)}
.foot{border-top:1px solid var(--line-soft);padding:1.5rem;display:flex;flex-wrap:wrap;align-items:center;gap:1rem;justify-content:space-between;
  font-family:var(--sans);font-size:.9rem;color:var(--ink-2)}
.foot a{color:var(--ink)}
.notfound{padding:4rem 1.25rem}
@media(max-width:59.99rem){
  .hud{font-size:.85rem;padding:.55rem .8rem .6rem}
  .hud .hud-sub{font-size:.74rem}
  .topnav{display:none}
  .mobile-nav{display:block}
  .mobile-nav nav{display:flex;flex-direction:column}
  .mobile-nav nav a{color:var(--ink-2);text-decoration:none;padding:.5rem 0}
  .mobile-nav{padding:.2rem 1rem}
  .mobile-nav summary{list-style:none;cursor:pointer;min-height:44px;display:flex;align-items:center}
  .mobile-nav summary::-webkit-details-marker{display:none}
  .stage{top:3rem;height:40svh}
  .step{min-height:54vh}
  .vlab{font-size:.95rem}
  .hero{min-height:100svh}
  .tri-grid{grid-template-columns:1fr}
}
@media(min-width:60rem){
  .tri-grid{grid-template-columns:repeat(3,1fr)}
}
@media(max-height:740px){.stage{height:36lvh}}
@media(min-width:60rem){
  .scrolly{display:grid;grid-template-columns:minmax(20rem,27rem) 1fr;gap:2rem;max-width:90rem;margin:0 auto}
  .stage{grid-column:2;grid-row:1;top:3.2rem;height:calc(100lvh - 3.2rem);align-self:start}
  #scara{grid-column:1;grid-row:1}
}
@media(min-width:60rem) and (max-height:740px){.stage{height:calc(100lvh - 3.2rem)}}
@media(prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *{animation:none!important;transition:none!important}
}
@media print{.topbar,.rail,.progress,.stage,.to-top,.share,.picker{display:none}}


/* share row (standards/v2/tools/share_row.py) */
.share-row{display:flex;flex-wrap:wrap;gap:.35rem;align-items:center}
.share-row .lab{font-size:.95rem;margin-inline-end:.3rem}
.share-row a,.share-row button{display:inline-grid;place-items:center;flex:none;width:2.5rem;height:2.5rem;padding:0;border-radius:50%;border:1px solid var(--sr-line,color-mix(in srgb,currentColor 28%,transparent));background:transparent;color:var(--sr-ink,inherit);text-decoration:none;cursor:pointer;font:inherit;transition:color .15s,border-color .15s}
.share-row a:hover,.share-row button:hover,.share-row a:focus-visible,.share-row button:focus-visible{color:var(--sr-acc,inherit);border-color:var(--sr-acc,currentColor)}
.share-row [hidden]{display:none}
@media (pointer:coarse){.share-row a,.share-row button{width:2.75rem;height:2.75rem}}
@media (max-width:30rem){.share-row .lab{flex-basis:100%;margin:0 0 .15rem}}
.share-status{font-size:.92rem;color:var(--sr-ok,inherit);min-height:1.2em;margin:.4rem 0 0}
.share-status:empty{display:none}
.share-field{display:block;width:100%;max-width:36rem;margin-top:.4rem;font:inherit;font-size:.9rem}