/* Size Reduction Lab: shared styles. Colour tokens follow the gvisualizer study site (night default, day theme). */
:root{
  --night:#0C1A2B; --panel:#14263C; --panel-2:#1C3450; --edge:#2A4767; --ink:#EAF3FF; --dim:#8EA6C2;
  --flow:#3FD0E0; --heat:#FF8B5E; --gold:#FFC93F; --gold-deep:#A87B10; --good:#58DE8C; --bad:#FF5C7A; --violet:#B79CFF;
  --gold-soft:#3A3320; --shadow:#07111D; --gold-ink:#FFC93F; --on-accent:#0C1A2B; --bad-soft:#3D1A27; --rep-soft:#1E2F45; --good-soft:#15392A;
  /* chart series (validated for colour-vision deficiency against the panel surface) */
  --s1:#14A3B8; --s2:#E5653A; --s3:#9178E8; --s4:#C08A1C;
  --steel:#9FB3C8; --steel-dark:#5B6F86; --rock:#B49A7A; --rock-dark:#7A634A;
  --f-display:"Fredoka","Trebuchet MS",system-ui,sans-serif;
  --f-body:"Nunito",system-ui,-apple-system,"Segoe UI",sans-serif;
  --r:12px; --head-h:64px;
  color-scheme:dark;
}
:root[data-theme="light"]{
  --night:#F3F6FA; --panel:#FFFFFF; --panel-2:#E8EEF6; --edge:#C8D4E2; --ink:#14223A; --dim:#55667D;
  --flow:#0B7C8C; --heat:#C8481F; --gold:#F2B52E; --gold-deep:#B98612; --good:#1E8A4C; --bad:#C42A4A; --violet:#6A4FC9;
  --gold-soft:#FFF3D6; --shadow:#C3CFDD; --gold-ink:#8A6100; --on-accent:#14223A; --bad-soft:#FBE3E8; --rep-soft:#E2F2F5; --good-soft:#E3F5EA;
  --s1:#0089A0; --s2:#C8481F; --s3:#6A4FC9; --s4:#B98612;
  --steel:#7F93A8; --steel-dark:#4A5C70; --rock:#A0835F; --rock-dark:#6B5236;
  color-scheme:light;
}
*,*::before,*::after{box-sizing:border-box}
[hidden]{display:none!important}
html,body{background:var(--night);color:var(--ink);margin:0}
body{font-family:var(--f-body);font-size:16px;line-height:1.6;overflow-x:clip;background:radial-gradient(1200px 600px at 50% -10%,var(--panel-2),var(--night) 70%) fixed,var(--night)}
a{color:var(--flow)}
button,input,select{font:inherit;color:inherit}
:focus-visible{outline:3px solid var(--gold);outline-offset:2px}
.wrap{max-width:1240px;margin:0 auto;padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px));padding-block:0 24px}

/* header */
.top{position:sticky;top:0;z-index:30;display:flex;align-items:center;gap:6px 12px;min-height:var(--head-h);padding:8px 0;background:var(--panel)}
.top::before{content:'';position:absolute;top:0;bottom:0;left:50%;width:100vw;transform:translateX(-50%);background:var(--panel);border-bottom:1px solid var(--edge);z-index:-1}
.logo{display:inline-flex;align-items:center;gap:9px;text-decoration:none;color:var(--ink);font-family:var(--f-display);font-weight:700;font-size:19px;letter-spacing:-.01em;flex:none}
.logo .mark{display:grid;place-items:center;width:34px;height:34px;border-radius:10px;background:var(--gold);color:var(--on-accent)}
.logo .mark svg{display:block}
.tabs{display:flex;align-items:stretch;gap:2px;margin-right:auto;overflow-x:auto;scrollbar-width:none;align-self:stretch;min-width:0}
.tabs::-webkit-scrollbar{display:none}
.tabs a{display:flex;align-items:center;padding:8px 12px 5px;font-weight:600;font-size:15px;color:var(--dim);text-decoration:none;border-bottom:3px solid transparent;white-space:nowrap;margin-bottom:-8px}
.tabs a:hover{color:var(--ink)}
.tabs a.on{color:var(--ink);border-bottom-color:var(--gold)}
.iconbtn{display:inline-grid;place-items:center;width:38px;height:38px;padding:0;border-radius:999px;background:transparent;border:1px solid var(--edge);color:var(--ink);cursor:pointer;flex:none}
.iconbtn:hover{background:var(--panel-2)}
.iconbtn svg{display:block}
@media (max-width:820px){
  .top{gap:4px 8px;flex-wrap:wrap;padding:8px 0 0}
  .logo{font-size:17px}
  .themebtn{margin-left:auto}
  .tabs{order:10;flex:1 0 100%;margin:0;height:42px}
  .tabs a{padding:6px 10px 3px;font-size:14.5px;margin-bottom:0}
}

/* page heading */
h1{font-family:var(--f-display);font-weight:700;font-size:clamp(26px,3.8vw,36px);line-height:1.15;letter-spacing:-.01em;margin:22px 0 6px;text-wrap:balance}
h2{font-family:var(--f-display);font-weight:700;font-size:22px;letter-spacing:-.01em;margin:0 0 8px}
h3{font-family:var(--f-display);font-weight:600;font-size:18px;margin:0 0 6px}
.lede{color:var(--dim);margin:0 0 18px;max-width:78ch}
.kicker{font-weight:700;font-size:12px;letter-spacing:.09em;text-transform:uppercase;color:var(--flow);margin:22px 0 0}

/* lab layout: stage (canvas + results) and control panel */
.lab{display:grid;grid-template-columns:minmax(0,1fr) 340px;gap:18px;align-items:start}
.lab.wide-ctl{grid-template-columns:minmax(0,1fr) 380px}
@media (max-width:980px){ .lab,.lab.wide-ctl{grid-template-columns:minmax(0,1fr)} }
.card{background:var(--panel);border:1px solid var(--edge);border-radius:var(--r);padding:16px 18px;min-width:0;max-width:100%}
.card + .card{margin-top:14px}
.stage{padding:0;overflow:hidden}
.stage-bar{display:flex;flex-wrap:wrap;align-items:center;gap:8px;padding:10px 12px;border-bottom:1px solid var(--edge);background:var(--panel-2)}
.stage-bar .title{font-weight:700;font-size:15px;margin-right:auto}
.canvas-box{position:relative;width:100%;background:var(--panel)}
.canvas-box canvas{display:block;width:100%;height:100%;touch-action:pan-y}
.legend-row{display:flex;flex-wrap:wrap;gap:6px 14px;padding:8px 12px 10px;font-size:13px;color:var(--dim);border-top:1px solid var(--edge)}
.legend-row i{display:inline-block;width:12px;height:12px;border-radius:3px;margin-right:5px;vertical-align:-1px}
.legend-row i.line{height:3px;border-radius:2px;vertical-align:3px;width:16px}
.legend-row i.dash{height:0;border-top:2px dashed currentColor;background:none!important;width:16px;vertical-align:3px;border-radius:0}

/* controls */
.ctl{display:grid;gap:14px}
.ctl-group{display:grid;gap:12px}
.ctl-group + .ctl-group{border-top:1px solid var(--edge);padding-top:12px}
.ctl-group > .gt{font-weight:700;font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:var(--dim);margin:0}
.slider{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:2px 10px;align-items:center}
.slider label{font-weight:600;font-size:14.5px;line-height:1.3}
.slider label small{display:block;font-weight:400;color:var(--dim);font-size:12.5px}
.numbox{display:inline-flex;align-items:center;gap:4px;background:var(--panel-2);border:1px solid var(--edge);border-radius:8px;padding:2px 8px 2px 4px}
.numbox input{width:74px;background:transparent;border:0;text-align:right;font-weight:700;font-variant-numeric:tabular-nums;padding:3px 2px;outline:none;-moz-appearance:textfield}
.numbox input::-webkit-outer-spin-button,.numbox input::-webkit-inner-spin-button{-webkit-appearance:none;margin:0}
.numbox:focus-within{border-color:var(--gold)}
.numbox .u{color:var(--dim);font-size:13px;white-space:nowrap}
.slider input[type=range]{grid-column:1/-1;width:100%;margin:4px 0 0;accent-color:var(--gold);height:22px;cursor:pointer}
.field{display:grid;gap:4px}
.field label{font-weight:600;font-size:14.5px}
select.sel{width:100%;background:var(--panel-2);border:1px solid var(--edge);border-radius:8px;padding:8px 10px}
.seg{display:inline-flex;flex-wrap:wrap;gap:4px;padding:3px;background:var(--panel-2);border-radius:999px;max-width:100%}
.seg button{background:transparent;border:none;padding:6px 12px;border-radius:999px;font-weight:600;font-size:14px;cursor:pointer;color:var(--dim);white-space:nowrap}
.seg button.on{background:var(--gold);color:var(--on-accent)}
.check{display:flex;gap:8px;align-items:center;font-size:14.5px;cursor:pointer}
.check input{accent-color:var(--gold);width:17px;height:17px}
.btn{font-weight:700;font-size:14.5px;padding:8px 16px;border-radius:999px;background:var(--gold);color:var(--on-accent);border:1px solid var(--gold);text-decoration:none;display:inline-flex;align-items:center;gap:6px;cursor:pointer;line-height:1.3}
.btn:hover{background:var(--gold-deep);border-color:var(--gold-deep)}
.btn.ghost{background:transparent;color:var(--ink);border:1px solid var(--edge)}
.btn.ghost:hover{background:var(--panel-2)}
.btn.sm{font-size:13.5px;padding:5px 12px}
.btn svg{display:block}
.btnrow{display:flex;flex-wrap:wrap;gap:8px}

/* results */
.results{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:10px}
.res{background:var(--panel-2);border:1px solid var(--edge);border-radius:10px;padding:10px 12px;min-width:0}
.res .k{font-size:12.5px;font-weight:700;color:var(--dim);letter-spacing:.02em;line-height:1.3}
.res .v{font-family:var(--f-display);font-weight:600;font-size:28px;line-height:1.15;font-variant-numeric:tabular-nums;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.res .v small{font-family:var(--f-body);font-size:14px;font-weight:600;color:var(--dim);margin-left:4px}
.res .s{font-size:12.5px;color:var(--dim);line-height:1.35}
.res.hl{border-color:var(--gold);background:var(--gold-soft)}
.res.good{border-color:var(--good);background:var(--good-soft)}
.res.bad{border-color:var(--bad);background:var(--bad-soft)}
.badge{display:inline-flex;align-items:center;gap:6px;font-weight:700;font-size:13px;padding:3px 10px;border-radius:999px;background:var(--panel);border:1px solid var(--edge)}
.badge.good{color:var(--good);border-color:var(--good)}
.badge.bad{color:var(--bad);border-color:var(--bad)}
.badge.warn{color:var(--gold-ink);border-color:var(--gold)}
.badge.info{color:var(--flow);border-color:var(--flow)}

/* explanation sections */
.sections{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:14px;margin-top:14px}
@media (max-width:980px){ .sections{grid-template-columns:minmax(0,1fr)} }
.prose p{margin:0 0 10px}
.prose ul,.prose ol{margin:0 0 10px;padding-left:22px}
.prose li{margin-bottom:5px}
.try{list-style:none;padding:0;margin:0;display:grid;gap:10px;counter-reset:t}
.try li{counter-increment:t;display:grid;grid-template-columns:28px minmax(0,1fr);gap:4px 10px;align-items:start;background:var(--panel-2);border:1px solid var(--edge);border-radius:10px;padding:10px 12px}
.try li::before{content:counter(t);display:grid;place-items:center;width:26px;height:26px;border-radius:999px;background:var(--gold);color:var(--on-accent);font-weight:800;font-size:14px}
.try li p{margin:0 0 6px;font-size:15px}
.try li .btn{justify-self:start}
.examples{margin-top:14px}
.ex{border:1px solid var(--edge);border-radius:var(--r);background:var(--panel);margin-top:12px;overflow:hidden}
.ex > summary{list-style:none;cursor:pointer;display:flex;flex-wrap:wrap;align-items:center;gap:8px 12px;padding:14px 18px;background:var(--panel-2)}
.ex > summary::-webkit-details-marker{display:none}
.ex > summary::after{content:'';width:9px;height:9px;border-right:2px solid var(--dim);border-bottom:2px solid var(--dim);transform:rotate(45deg);margin-left:auto;transition:transform .15s}
.ex[open] > summary::after{transform:rotate(225deg)}
.ex .exn{font-weight:800;color:var(--gold-ink);font-size:14px}
.ex .ext{font-weight:700;font-size:16px;flex:1 1 260px;min-width:0}
.ex .src{font-size:12.5px;color:var(--dim);flex-basis:100%}
.ex-body{padding:14px 18px 16px}
.ex-body .q{background:var(--rep-soft);border-left:4px solid var(--flow);border-radius:0 10px 10px 0;padding:10px 14px;margin:0 0 12px}
.steps{list-style:none;padding:0;margin:0;display:grid;gap:8px;counter-reset:s}
.steps li{counter-increment:s;position:relative;padding:8px 12px 8px 44px;border:1px solid var(--edge);border-radius:10px;background:var(--panel)}
.steps li::before{content:counter(s);position:absolute;left:10px;top:9px;width:24px;height:24px;border-radius:999px;display:grid;place-items:center;font-weight:800;font-size:13px;background:var(--panel-2);color:var(--ink);border:1px solid var(--edge)}
.steps li p{margin:0 0 4px}
.answer{margin:12px 0 0;background:var(--good-soft);border:1px solid color-mix(in srgb,var(--good) 45%,transparent);border-left:5px solid var(--good);border-radius:var(--r);padding:10px 14px}
.answer b.k{display:block;font-weight:800;font-size:12px;letter-spacing:.08em;text-transform:uppercase;color:var(--good)}
.note{border-left:4px solid var(--gold);background:var(--gold-soft);border-radius:0 10px 10px 0;padding:8px 12px;margin:10px 0;font-size:14.5px}
.note p{margin:0}
.mathbox{overflow-x:auto;overflow-y:hidden;max-width:100%;padding:2px 0}
.katex-display{margin:8px 0!important;overflow-x:auto;overflow-y:hidden;padding:2px 0}
.katex{font-size:1.06em}
.tw{overflow-x:auto;max-width:100%}
table.tbl{border-collapse:collapse;font-size:14px;width:100%}
table.tbl th,table.tbl td{border:1px solid var(--edge);padding:5px 8px;text-align:right;white-space:nowrap}
table.tbl th{background:var(--panel-2);font-weight:700;text-align:center}
table.tbl td:first-child,table.tbl th:first-child{text-align:left}
table.tbl input{width:78px;background:var(--panel-2);border:1px solid var(--edge);border-radius:6px;padding:3px 6px;text-align:right;font-variant-numeric:tabular-nums}
table.tbl input.lab-in{width:70px;text-align:left}
table.tbl tfoot td{font-weight:700;background:var(--panel-2)}

/* derivation stepper */
.deriv-steps{display:grid;gap:8px}
.dstep{border:1px solid var(--edge);border-radius:10px;padding:10px 14px;background:var(--panel-2)}
.dstep .dn{font-weight:800;color:var(--gold-ink);font-size:13px;letter-spacing:.04em;text-transform:uppercase}
.deriv-grid{display:grid;grid-template-columns:260px minmax(0,1fr);gap:16px;align-items:start}
@media (max-width:760px){ .deriv-grid{grid-template-columns:minmax(0,1fr)} .deriv-grid svg{max-width:280px;margin:0 auto} }

/* hub */
.hero{display:grid;grid-template-columns:minmax(0,1.2fr) minmax(0,1fr);gap:24px;align-items:center;margin:10px 0 6px}
@media (max-width:860px){ .hero{grid-template-columns:minmax(0,1fr)} }
.hero-art{background:var(--panel);border:1px solid var(--edge);border-radius:18px;padding:10px;min-width:0}
.hero-art canvas{display:block;width:100%;aspect-ratio:16/10}
.modgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(270px,1fr));gap:14px;margin-top:18px}
.mod{display:flex;flex-direction:column;gap:8px;background:var(--panel);border:1px solid var(--edge);border-radius:16px;padding:16px;text-decoration:none;color:var(--ink);transition:border-color .15s,transform .15s}
.mod:hover{border-color:var(--gold);transform:translateY(-2px)}
.mod svg{width:100%;height:auto;max-height:130px;display:block;background:var(--panel-2);border-radius:12px}
.mod h3{margin:4px 0 0;font-size:19px}
.mod p{margin:0;color:var(--dim);font-size:14.5px}
.chips{display:flex;flex-wrap:wrap;gap:6px;margin-top:auto}
.chip{font-weight:600;font-size:12px;padding:2px 9px;border-radius:999px;background:var(--panel-2);color:var(--dim);border:1px solid var(--edge)}
.featlist{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:12px;margin-top:14px}
.feat{background:var(--panel);border:1px solid var(--edge);border-radius:var(--r);padding:12px 14px}
.feat b{display:block;font-size:15px}
.feat span{color:var(--dim);font-size:14px}

/* footer */
.foot{margin-top:34px;padding:16px 0 8px;border-top:1px solid var(--edge);color:var(--dim);font-size:13.5px;display:flex;flex-wrap:wrap;gap:6px 18px;justify-content:space-between}
.foot a{color:var(--dim)}

/* small screens */
@media (max-width:980px){
  /* phone and tablet: animation first, then its controls, then the results */
  .lab > div{display:contents}
  .lab > div > .stage{order:1}
  .lab > aside{order:2}
  .lab > div > .card:not(.stage){order:3}
  .lab > div > .card + .card{margin-top:0}
}
@media (max-width:520px){
  .card{padding:14px}
  .card.stage{padding:0}
  .res .v{font-size:23px}
  .ex > summary{padding:12px 14px}
  .ex-body{padding:12px 14px}
  .steps li{padding-left:40px}
  .numbox input{width:64px}
}
@media (prefers-reduced-motion:reduce){ *{scroll-behavior:auto!important} .mod{transition:none} }
section[id],.card[id],h2[id]{scroll-margin-top:calc(var(--head-h) + 14px)}
@media (max-width:820px){ section[id],.card[id],h2[id]{scroll-margin-top:112px} }

.alllabs{display:inline-grid;place-items:center;width:36px;height:36px;border-radius:999px;border:1px solid var(--edge);color:var(--ink);text-decoration:none;margin-right:8px;flex:none}
.alllabs:hover{background:var(--panel-2)}