/* Fourier Pen. Ledger house style: see DESIGN_STANDARDS.md. Self-hosted fonts, square
   corners, no shadows, no transitions, two accents with fixed jobs. */

@font-face{font-family:"Source Serif 4";src:url("fonts/SourceSerif4-400.woff2")format("woff2");font-weight:400;font-style:normal;font-display:swap}
@font-face{font-family:"Source Serif 4";src:url("fonts/SourceSerif4-600.woff2")format("woff2");font-weight:600;font-style:normal;font-display:swap}
@font-face{font-family:"IBM Plex Sans";src:url("fonts/IBMPlexSans-400.woff2")format("woff2");font-weight:400;font-style:normal;font-display:swap}
@font-face{font-family:"IBM Plex Sans";src:url("fonts/IBMPlexSans-600.woff2")format("woff2");font-weight:600;font-style:normal;font-display:swap}
@font-face{font-family:"IBM Plex Mono";src:url("fonts/IBMPlexMono-400.woff2")format("woff2");font-weight:400;font-style:normal;font-display:swap}

:root{
  --paper:#EDEDE7; --panel:#F5F5F0; --ink:#1C1E1B; --ink-2:#52564E;
  --rule:#C6C7BF; --edge:#767A70; --signal:#8C3A1E; --signal-2:#2C5852;
  --font-head:"Source Serif 4","Iowan Old Style","Palatino Linotype",Palatino,serif;
  --font-body:"IBM Plex Sans","Helvetica Neue",Helvetica,Arial,sans-serif;
  --font-mono:"IBM Plex Mono","SF Mono",Menlo,Consolas,monospace;
  --s1:8px; --s2:16px; --s3:24px; --s4:40px; --s5:64px; --s6:96px;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --paper:#191B18; --panel:#212420; --ink:#E6E6DE; --ink-2:#A2A69B;
  --rule:#3B3F38; --edge:#6A6F66; --signal:#D8825C; --signal-2:#74AFA5; color-scheme:dark;}}
:root[data-theme="dark"]{
  --paper:#191B18; --panel:#212420; --ink:#E6E6DE; --ink-2:#A2A69B;
  --rule:#3B3F38; --edge:#6A6F66; --signal:#D8825C; --signal-2:#74AFA5; color-scheme:dark;}

*,*::before,*::after{box-sizing:border-box;border-radius:0}
[hidden]{display:none !important}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--font-body);
  font-size:15px;line-height:1.5;-webkit-font-smoothing:antialiased;
  padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px));
  padding-bottom:var(--s2)}
/* Desktop: the stage and the panel share one height, sized so the whole page fits the viewport.
   220px is the writeup bar, header, note, footer and gaps. */
:root{--fit:clamp(420px,calc(100vh - 220px),1400px)}
a{color:var(--signal);text-underline-offset:2px}
a:hover{color:var(--ink)}
a:focus-visible,button:focus-visible,input:focus-visible,select:focus-visible,[tabindex]:focus-visible,.drop:focus-within{
  outline:2px solid var(--signal);outline-offset:2px}
.skip-link{position:absolute;left:-9999px}
.skip-link:focus{left:var(--s2);top:var(--s2);background:var(--panel);border:1px solid var(--edge);padding:var(--s1);z-index:10}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}

.writeup-bar{display:block;margin:0 calc(-1 * max(16px,env(safe-area-inset-left,0px))) 0 calc(-1 * max(16px,env(safe-area-inset-right,0px)));
  background:var(--ink);color:var(--paper);text-align:center;padding:10px 18px;
  font:600 14px/1.4 var(--font-body);text-decoration:none}
.writeup-bar:hover{color:var(--paper);text-decoration:underline}

.app{max-width:1400px;margin:0 auto;display:grid;gap:var(--s2);padding-top:var(--s2)}
header.top{display:grid;grid-template-columns:auto minmax(0,1fr) auto;gap:var(--s1) var(--s3);align-items:center;
  border-bottom:2px solid var(--ink);padding-bottom:var(--s1)}
h1{font-family:var(--font-head);font-weight:600;font-size:clamp(1.6rem,2.6vw,2.2rem);line-height:1.1;margin:0;letter-spacing:-.01em;white-space:nowrap}
.tagline{margin:0;color:var(--ink-2);max-width:78ch;font-size:13px;line-height:1.4;text-wrap:pretty}

.layout{display:grid;grid-template-columns:minmax(0,1fr) 360px;gap:var(--s2);align-items:start}
@media (max-width:880px){.layout{grid-template-columns:minmax(0,1fr)}}

/* Stage */
.stage-wrap{display:grid;gap:var(--s1)}
.stage{position:relative;width:100%;height:var(--fit);background:var(--panel);border:1px solid var(--rule);overflow:hidden}
@media (max-width:880px){.stage{height:auto;aspect-ratio:1/1}}
#stage{position:absolute;inset:0;width:100%;height:100%;display:block;touch-action:none}
.stage-bar{position:absolute;top:var(--s1);right:var(--s1);left:var(--s1);display:flex;justify-content:space-between;gap:var(--s1);pointer-events:none}
.stage-bar>*{pointer-events:auto}
.btn-row{display:flex;gap:6px;flex-wrap:wrap;justify-content:flex-end}
.readout{position:absolute;left:12px;bottom:8px;right:12px;font:12px/1.4 var(--font-mono);color:var(--ink-2);pointer-events:none}
.readout b{color:var(--signal);font-weight:400}
.status{position:absolute;inset:0;display:grid;place-items:center;padding:var(--s3);pointer-events:none}
.status>div{background:var(--paper);border:1px solid var(--edge);padding:var(--s2);max-width:34ch;text-align:center;font-size:14.5px;pointer-events:auto}
.progress{position:absolute;left:0;right:0;bottom:0;height:4px;background:var(--rule)}
.progress>i{display:block;height:100%;width:0;background:var(--signal)}
.stage-note{margin:0;font-size:12px;color:var(--ink-2);line-height:1.4}

/* Panel */
.panel{background:var(--panel);border:1px solid var(--rule);display:grid;align-content:start;min-width:0;overflow-x:hidden}
@media (min-width:881px){.panel{height:var(--fit);overflow-y:auto;grid-template-rows:auto 1fr}}
.tabs{display:grid;grid-template-columns:repeat(5,1fr);border-bottom:1px solid var(--rule);background:var(--paper)}
.tab{font:600 12.5px/1 var(--font-body);color:var(--ink-2);background:var(--paper);border:0;border-right:1px solid var(--rule);padding:12px 4px;cursor:pointer;text-align:center}
.tab:last-child{border-right:0}
.tab:hover{color:var(--ink)}
.tab[aria-selected="true"]{background:var(--panel);color:var(--ink);border-bottom:2px solid var(--ink);margin-bottom:-1px}
.tab:focus-visible{outline-offset:-2px}
.more{border:1px solid var(--rule);background:var(--paper)}
.more summary{cursor:pointer;padding:8px 10px;font-size:13px;font-weight:600;list-style:none;display:flex;justify-content:space-between}
.more summary::after{content:"Show";font-weight:400;color:var(--ink-2);font-size:12.5px}
.more[open] summary::after{content:"Hide"}
.more summary::-webkit-details-marker{display:none}
.more-body{display:grid;gap:12px;padding:0 10px 12px;border-top:1px solid var(--rule);padding-top:12px}
.group{padding:var(--s2);display:grid;gap:11px;align-content:start;min-width:0}
.group h2{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap} /* the tab is the visible label */
.drop{display:grid;gap:2px;padding:14px;border:1px dashed var(--edge);text-align:center;cursor:pointer;background:var(--paper)}
.drop strong{font-weight:600}
.drop span{color:var(--ink-2);font-size:12.5px}
.drop:hover,.drop.over{border-color:var(--ink);border-style:solid}
.prompt-row{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:6px}
.samples{display:flex;flex-wrap:wrap;gap:6px;align-items:center}
.samples>span{color:var(--ink-2);font-size:12.5px;margin-right:2px}
.chip{font:500 12.5px/1 var(--font-body);color:var(--ink);background:var(--panel);border:1px solid var(--edge);padding:7px 10px;cursor:pointer}
.chip:hover{border-color:var(--ink)}
.chip[aria-pressed="true"]{background:var(--ink);color:var(--paper);border-color:var(--ink)}
.previews{display:grid;grid-template-columns:1fr 1fr;gap:var(--s1)}
.previews figure{margin:0;display:grid;gap:4px}
.prev-box{position:relative}
.previews canvas{width:100%;max-width:100%;aspect-ratio:1;background:var(--paper);border:1px solid var(--rule);display:block}
.prev-skel{position:absolute;inset:0;height:auto;margin:0}
.previews figcaption{font-size:12px;color:var(--ink-2)}

.field{display:grid;gap:4px}
.field-head{display:flex;justify-content:space-between;gap:var(--s1);align-items:baseline}
.field label,.lbl{font-weight:600;font-size:13.5px}
.field output{font:12px var(--font-mono);color:var(--ink-2);font-variant-numeric:tabular-nums}
.hint{font-size:12.5px;color:var(--ink-2)}
input[type="range"]{width:100%;accent-color:var(--signal);margin:2px 0}
select,input[type="text"],input[type="number"]{font:inherit;color:var(--ink);background:var(--paper);border:1px solid var(--edge);padding:6px 8px;width:100%;min-width:0}
input[type="color"]{width:100%;height:34px;padding:2px;background:var(--paper);border:1px solid var(--edge);cursor:pointer}
.seg{display:grid;grid-template-columns:1fr 1fr;border:1px solid var(--edge)}
.seg label{position:relative;display:block;text-align:center;padding:7px 6px;cursor:pointer;font-weight:500;font-size:12.5px;line-height:1.25}
.seg label+label{border-left:1px solid var(--edge)}
.seg input{position:absolute;opacity:0;inset:0;margin:0;cursor:pointer}
.seg label:has(input:checked){background:var(--ink);color:var(--paper)}
.seg label:has(input:focus-visible){outline:2px solid var(--signal);outline-offset:-2px}
.toggles{display:grid;gap:6px}
.toggles label{display:flex;gap:var(--s1);align-items:center;cursor:pointer;font-size:13.5px}
.toggles input{accent-color:var(--signal);width:16px;height:16px;margin:0}
.row2{display:grid;grid-template-columns:1fr 1fr;gap:var(--s1);align-items:end}

.formula{font-family:var(--font-head);font-size:18px;font-style:italic;text-align:center;padding:2px 0 0;overflow-x:auto;white-space:nowrap}
.formula .frac{display:inline-flex;flex-direction:column;vertical-align:middle;font-size:13px;line-height:1.15;margin:0 2px}
.formula .frac span:first-child{border-bottom:1px solid currentColor;padding:0 2px}
.formula sub,.formula sup{font-size:.62em}
.small{margin:0;font-size:12.5px;color:var(--ink-2);text-wrap:pretty}
.eq{font:12px/1.7 var(--font-mono);color:var(--ink);background:var(--paper);border:1px solid var(--rule);padding:8px 10px;overflow-x:auto;white-space:nowrap}
.eq sup{font-size:.8em}
.tbl-wrap{overflow-x:auto}
table.coef{width:100%;border-collapse:collapse;font-size:12px}
table.coef th{text-align:left;font-weight:600;color:var(--ink-2);font-size:11px;text-transform:uppercase;letter-spacing:.06em;padding:4px 6px 4px 0;border-bottom:2px solid var(--ink);white-space:nowrap}
table.coef td{padding:2px 6px 2px 0;border-bottom:1px solid var(--rule);vertical-align:top}
table.coef th.num,table.coef td.num{font-family:var(--font-mono);text-align:right;font-variant-numeric:tabular-nums}
table.coef td:first-child{color:var(--ink-2)}
table.coef td .bar{display:inline-block;height:6px;background:var(--signal-2);vertical-align:middle;margin-right:6px}
dl.stats{display:grid;grid-template-columns:1fr auto;gap:2px 12px;margin:0;font-size:12.5px}
dl.stats dt{color:var(--ink-2)}
dl.stats dd{margin:0;text-align:right;font:12px var(--font-mono);font-variant-numeric:tabular-nums;white-space:nowrap}
dl.stats-2{grid-template-columns:1fr auto}

.btn{font-family:var(--font-body);font-size:13.5px;line-height:1.2;padding:9px 12px;background:var(--panel);color:var(--ink);border:1px solid var(--edge);cursor:pointer;text-align:left}
.btn:hover:not(:disabled){background:var(--paper);border-color:var(--ink)}
.btn:disabled{color:var(--ink-2);border-color:var(--rule);cursor:not-allowed}
.btn-primary{background:var(--signal);color:var(--paper);border-color:var(--signal)}
.btn-primary:hover:not(:disabled){background:var(--ink);border-color:var(--ink);color:var(--paper)}
.btn-primary:disabled{background:var(--rule);border-color:var(--rule);color:var(--ink-2)}
.btn-small{font-size:12px;padding:6px 10px}
.btn[aria-pressed="true"]{background:var(--ink);color:var(--paper);border-color:var(--ink)}
.save-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:6px}
.btn.save{display:grid;gap:2px;text-align:center;padding:8px 4px}
.btn.save b{font-weight:600;font-size:13.5px}
.btn.save span{color:var(--ink-2);font-size:11.5px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.export-preview{margin:0;display:grid;gap:4px}
.export-preview canvas{display:block;max-width:200px;width:100%;height:auto;border:1px solid var(--rule);background:var(--paper)}
.export-preview figcaption{font-size:11.5px;color:var(--ink-2);font-family:var(--font-mono);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}

/* Skeleton: flat fill with an opacity pulse. Never a gradient sweep. */
.skeleton{background:var(--rule);height:14px;margin-bottom:var(--s1)}
@media (prefers-reduced-motion:no-preference){
  .skeleton{animation:ledger-sk 1.6s ease-in-out infinite}
  @keyframes ledger-sk{0%,100%{opacity:1}50%{opacity:.55}}}

.site-footer{margin-top:0;padding-top:var(--s1);border-top:1px solid var(--rule);font-size:12px;color:var(--ink-2);display:flex;flex-wrap:wrap;gap:var(--s1) var(--s2)}

/* Document pages (privacy, terms) */
body.doc{padding-bottom:var(--s6)}
body.doc .wrap{max-width:68ch;margin:0 auto;padding:var(--s5) 0}
body.doc h1{font-size:2.44rem;margin:0 0 var(--s2)}
body.doc h2{font-family:var(--font-head);font-weight:600;font-size:1.56rem;line-height:1.15;margin:var(--s4) 0 var(--s2);padding-bottom:var(--s1);border-bottom:2px solid var(--ink)}
body.doc p{margin:0 0 var(--s2);max-width:68ch;font-size:16px;line-height:1.6}
body.doc .meta{font-size:.8rem;text-transform:uppercase;letter-spacing:.06em;color:var(--ink-2);margin-bottom:var(--s1)}
body.doc .lede{font-family:var(--font-head);font-size:1.25rem;color:var(--ink-2)}
body.doc .site-footer a{margin-right:var(--s2)}

@media (max-width:880px){header.top{grid-template-columns:1fr auto}header.top .tagline{grid-column:1 / -1}header.top .btn{justify-self:end}h1{white-space:normal}}
@media (max-width:600px){
  .row2{grid-template-columns:1fr}
  .save-grid{grid-template-columns:repeat(2,1fr)}
}