:root{
  --ink:#16202b; --ink2:#3a4654; --paper:#f6f3e8; --grid:#e1dbc6; --grid2:#cfc7ab;
  --panel:#fffdf7; --accent:#0d4f8b; --accent-ink:#ffffff; --line:#cfc8b3; --focus:#c2410c;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color:var(--ink); background:var(--paper);
}
*{box-sizing:border-box}
html,body{margin:0;height:100%}
body{line-height:1.45}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}
.skip{position:absolute;left:-999px;top:0;background:var(--ink);color:#fff;padding:.5rem .8rem;z-index:10}
.skip:focus{left:.5rem;top:.5rem}
:focus-visible{outline:3px solid var(--focus);outline-offset:2px}

.top{display:flex;align-items:center;justify-content:space-between;gap:1rem;padding:.55rem 1rem;border-bottom:2px solid var(--ink);background:var(--panel)}
.title{display:flex;align-items:baseline;gap:.6rem;flex-wrap:wrap}
.fig{font-family:"Courier New",Courier,monospace;font-weight:700;letter-spacing:.08em;background:var(--ink);color:#fff;padding:.1rem .45rem;border-radius:3px}
h1{font-family:"Courier New",Courier,monospace;text-transform:uppercase;letter-spacing:.12em;font-size:1.35rem;margin:0}
.sub{color:var(--ink2);font-size:.95rem}
.toggles{display:flex;gap:.6rem;align-items:center;flex-wrap:wrap}
.toggles button,.btn{font:inherit;font-size:.9rem;border:2px solid var(--ink);background:#fff;color:var(--ink);border-radius:6px;padding:.3rem .7rem;cursor:pointer}
.toggles button[aria-pressed="true"]{background:var(--ink);color:#fff}
.rm{font-size:.9rem;display:flex;gap:.35rem;align-items:center;cursor:pointer}
.rm input{width:1.1rem;height:1.1rem;accent-color:var(--accent)}

.layout{display:grid;grid-template-columns:minmax(0,1fr) 410px;grid-template-rows:minmax(0,1fr) auto;
  grid-template-areas:"stage panel" "stats panel";height:calc(100vh - 58px);min-height:560px}
.stage{grid-area:stage;position:relative;overflow:hidden;
  background-color:var(--paper);
  background-image:
    linear-gradient(var(--grid2) 1px,transparent 1px),linear-gradient(90deg,var(--grid2) 1px,transparent 1px),
    linear-gradient(var(--grid) 1px,transparent 1px),linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:100px 100px,100px 100px,20px 20px,20px 20px}
#scene{display:block;width:100%;height:100%;touch-action:none;cursor:grab}
#scene:active{cursor:grabbing}
.hint{position:absolute;right:.6rem;top:.4rem;margin:0;font-size:.8rem;color:var(--ink2);background:rgba(255,253,247,.85);padding:.15rem .45rem;border-radius:4px}
.scale-note{position:absolute;left:.6rem;bottom:.4rem;margin:0;font-size:.75rem;color:var(--ink2);background:rgba(255,253,247,.85);padding:.1rem .4rem;border-radius:4px}
#partinfo{position:absolute;left:.6rem;top:.5rem;max-width:min(330px,70%);background:var(--ink);color:#fff;padding:.5rem .7rem;border-radius:6px;font-size:.9rem;box-shadow:0 3px 10px rgba(0,0,0,.2)}
#partinfo b{display:block;font-size:1rem;margin-bottom:.1rem}
#partinfo .chip{display:inline-block;width:.8rem;height:.8rem;border-radius:2px;margin-right:.35rem;vertical-align:-1px;border:1px solid #fff}
#flash{position:absolute;left:50%;top:12%;transform:translateX(-50%);font-family:"Courier New",monospace;font-weight:700;font-size:2.2rem;letter-spacing:.2em;color:var(--ink);opacity:0;transition:opacity .5s;pointer-events:none}
#flash.on{opacity:.9;transition:none}

.stats{grid-area:stats;border-top:2px solid var(--ink);background:var(--panel)}
.stats dl{display:grid;grid-template-columns:repeat(6,minmax(0,1fr));margin:0}
.stats dl>div{padding:.45rem .7rem;border-right:1px solid var(--line);min-width:0}
.stats dl>div:last-child{border-right:0}
.stats dt{font-size:.72rem;text-transform:uppercase;letter-spacing:.06em;color:var(--ink2);font-weight:600}
.stats dd{margin:0;font-family:"Courier New",monospace;font-weight:700;font-size:1.15rem;white-space:nowrap;font-variant-numeric:tabular-nums}
.stats .unit{font-size:.72rem;color:var(--ink2);display:block;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}

.panel{grid-area:panel;border-left:2px solid var(--ink);background:var(--panel);overflow-y:auto;padding:.8rem 1rem 1.2rem}
.steps{list-style:none;margin:0 0 .8rem;padding:0;display:grid;grid-template-columns:1fr 1fr;gap:.4rem}
.steps button{width:100%;text-align:left;font:inherit;font-size:.9rem;display:flex;gap:.45rem;align-items:center;border:2px solid var(--ink);background:#fff;color:var(--ink);border-radius:6px;padding:.32rem .5rem;cursor:pointer;min-height:2.4rem}
.steps button .n{font-family:"Courier New",monospace;font-weight:700;background:var(--ink);color:#fff;border-radius:50%;width:1.5rem;height:1.5rem;display:inline-flex;align-items:center;justify-content:center;flex:none;font-size:.85rem}
.steps button[aria-current="step"]{background:var(--accent);border-color:var(--accent);color:var(--accent-ink)}
.steps button[aria-current="step"] .n{background:#fff;color:var(--accent)}
.steps button:hover{background:#eef3f8}
.steps button[aria-current="step"]:hover{background:#0b467c}
#step-panel h2{margin:.2rem 0 .4rem;font-size:1.2rem}
#step-text p{margin:.3rem 0 .6rem}
.formula{font-family:"Times New Roman",Times,serif;font-size:1.25rem;font-style:italic;background:#fff;border:1px dashed var(--line);padding:.2rem .5rem;display:inline-block;border-radius:4px}
.ctl{margin:.6rem 0;padding:.6rem;border:1px solid var(--line);border-radius:6px;background:#fff}
.ctl label{display:flex;justify-content:space-between;font-weight:600;font-size:.92rem}
.ctl input[type=range]{width:100%;accent-color:var(--accent);height:1.6rem}
.ctl output,.mono{font-family:"Courier New",monospace;font-weight:700}
.readout{font-size:.9rem;margin:.25rem 0 0}
.btn{margin:.3rem .3rem 0 0}
.btn:disabled{opacity:.5;cursor:default}
table.ratios{border-collapse:collapse;width:100%;font-size:.88rem;margin:.4rem 0;background:#fff}
table.ratios th,table.ratios td{border:1px solid var(--line);padding:.25rem .4rem;text-align:left}
table.ratios td.r{font-family:"Courier New",monospace;font-weight:700;white-space:nowrap}
table.ratios caption{text-align:left;font-weight:700;margin-bottom:.2rem}
.parts h3{font-size:.85rem;margin:.6rem 0 .2rem;text-transform:uppercase;letter-spacing:.05em;color:var(--ink2)}
.parts ul{list-style:none;padding:0;margin:0;display:flex;flex-wrap:wrap;gap:.3rem}
.parts button{font:inherit;font-size:.82rem;border:1px solid var(--ink2);background:#fff;color:var(--ink);border-radius:4px;padding:.15rem .4rem;cursor:pointer}
.parts button .chip{display:inline-block;width:.7rem;height:.7rem;border-radius:2px;margin-right:.3rem;border:1px solid var(--ink)}
.parts button[aria-pressed="true"]{background:var(--ink);color:#fff}
.bigidea{margin-top:1rem;border-top:2px solid var(--ink);padding-top:.5rem}
.bigidea h2{font-size:1.05rem;margin:.2rem 0;font-family:"Courier New",monospace;text-transform:uppercase;letter-spacing:.08em}
.bigidea p{margin:.35rem 0;font-size:.93rem}
.noscript{padding:1rem}

@media (max-width: 860px){
  .layout{display:block;height:auto;min-height:0}
  .stage{height:50vh;min-height:300px}
  .stats dl{grid-template-columns:repeat(3,minmax(0,1fr))}
  .stats dl>div{border-bottom:1px solid var(--line);padding:.35rem .5rem}
  .stats dl>div:nth-child(3n){border-right:0}
  .stats dd{font-size:1rem}
  .panel{border-left:0;border-top:2px solid var(--ink);overflow:visible}
  .top{padding:.45rem .6rem;flex-wrap:wrap;gap:.4rem}
  .title{flex-wrap:nowrap}
  h1{font-size:1.05rem}
  .sub{display:none}
  .hint{font-size:.72rem}
  .scale-note{font-size:.68rem;right:.6rem}
}
@media (max-width: 420px){
  .toggles button{font-size:.8rem;padding:.25rem .45rem}
  .rm{font-size:.8rem}
  .stats dt{font-size:.66rem}
}
@media (prefers-reduced-motion: reduce){ #flash{transition:none} }

/* FIG. 2 additions */
#labels{position:absolute;inset:0;pointer-events:none;overflow:hidden}
#labels span{position:absolute;transform:translate(-50%,-50%);font-size:.74rem;font-weight:700;color:var(--ink);background:rgba(255,253,247,.9);border:1px solid var(--ink2);border-radius:4px;padding:.05rem .35rem;white-space:nowrap}
#labels span.dim{opacity:0}
.scale-note{max-width:calc(100% - 1.2rem)}
.btnrow{display:flex;flex-wrap:wrap;gap:.3rem;margin-top:.3rem}
.btnrow .btn{margin:0}
.warn{font-size:.88rem;background:#fff4e5;border:1px solid #e3b26b;border-radius:4px;padding:.3rem .5rem}
@media (max-width: 860px){ #labels span{font-size:.64rem;padding:0 .25rem} .scale-note{font-size:.62rem} }
/* four-stroke engine additions */
#flash{color:#b8860b}
#labels span.flow{font-size:.8rem;color:#fff;border:0;padding:.1rem .45rem}
#labels span.fi{background:rgba(43,111,208,.92)}
#labels span.fe{background:rgba(196,82,30,.92)}
.t-i{color:#2b6fd0;font-weight:700}
.t-e{color:#c4521e;font-weight:700}
.chart{margin:.6rem 0;padding:0}
.chart svg{width:100%;height:auto;display:block;background:#fffdf7;border:1px solid var(--line);border-radius:4px;font-family:"Courier New",monospace}
.chart figcaption{font-size:.82rem;margin-top:.3rem;line-height:1.45}
.key{display:inline-block;width:1.4em;height:.3em;vertical-align:middle;margin:0 .25em 0 .5em;border-radius:2px}
.key.k-i{background:#2b6fd0}.key.k-e{background:#e0662a}.key.k-r{background:repeating-linear-gradient(90deg,#55606b 0 6px,transparent 6px 9px)}
.persec{display:grid;grid-template-columns:1fr 1fr;gap:.4rem;margin:.6rem 0}
.persec>div{border:1px solid var(--line);border-radius:4px;padding:.35rem .5rem;background:#fffdf7}
.persec dt{font-size:.75rem;color:var(--ink2)}
.persec dd{margin:0;font-family:"Courier New",monospace;font-weight:700;font-size:1.1rem}
@media (max-width: 860px){ #labels span.flow{font-size:.66rem} }
/* bicycle drivetrain additions */
#flash{color:var(--accent);font-size:1.8rem;letter-spacing:.1em}
.shiftbar{display:flex;flex-wrap:wrap;align-items:center;gap:.35rem .45rem;padding:.4rem .7rem;border-top:1px solid var(--line)}
.shiftbar .btn{margin:0;min-height:2.3rem;min-width:4.6rem}
.shiftbar .btn[aria-pressed="true"]{background:var(--ink);color:#fff}
.shiftbar output{font-size:1.05rem;min-width:4.6rem;text-align:center}
.sb-label{font-size:.72rem;text-transform:uppercase;letter-spacing:.06em;color:var(--ink2);font-weight:600;margin-left:.3rem}
.stats dd.warn{color:#b3261e;background:none;border:0;padding:0;font-size:1.15rem}
.t-hi{color:#0e8fab;font-weight:700}
.tablewrap{overflow-x:auto;margin:.5rem 0}
#gear-table{border-collapse:collapse;width:100%;font-size:.8rem;background:#fff;font-variant-numeric:tabular-nums}
#gear-table caption{text-align:left;font-weight:700;margin-bottom:.2rem;font-size:.85rem}
#gear-table th,#gear-table td{border:1px solid var(--line);padding:.12rem .25rem;text-align:right;white-space:nowrap}
#gear-table thead th{text-align:center;font-size:.72rem}
#gear-table td.r2{background:#f6f8fa}
#gear-table td button{font:inherit;font-weight:700;border:0;background:none;color:var(--accent);cursor:pointer;padding:0;text-decoration:underline}
#gear-table td.x button{color:#b3261e}
#gear-table td.cur{outline:3px solid var(--accent);outline-offset:-3px}
#gear-table tr.now th{background:#e8eef5}
.note{font-size:.8rem;color:var(--ink2)}
@media (max-width: 860px){ .shiftbar{padding:.35rem .5rem} .shiftbar .btn{min-width:3.8rem;font-size:.85rem} }
.sb-group{display:inline-flex;align-items:center;gap:.4rem;margin-right:.6rem}
.sb-group .sb-label{margin-left:0}
/* printing press additions */
#flash{color:#5a3a1a}
.shiftbar .btn:disabled{opacity:.45;cursor:not-allowed}
.shiftbar .now-out{font-size:.9rem;min-width:12rem;text-align:left}
#run-table,table.small{border-collapse:collapse;width:100%;font-size:.84rem;background:#fff;font-variant-numeric:tabular-nums}
#run-table caption,table.small caption{text-align:left;font-weight:700;margin-bottom:.2rem;font-size:.85rem}
#run-table th,#run-table td,table.small th,table.small td{border:1px solid var(--line);padding:.15rem .35rem;text-align:left}
#run-table tr.now,#gov-table tr.now{background:#fff1c7}
#run-table tr.now td{font-weight:700}
#run-table tr.total td{font-weight:700}
#step-text ol{padding-left:1.3rem}
@media (max-width: 860px){ .shiftbar .now-out{min-width:0;font-size:.8rem} }

.top .fig{white-space:nowrap}
@media (max-width: 860px){ .top h1{font-size:1rem} }

/* steam engine additions */
#labels span.hot{background:rgba(196,110,30,.94)}
#labels span.cold{background:rgba(43,101,190,.94)}
table.small tr.total td,table.small tr.total th{font-weight:700}
.safety{margin:.7rem 0;padding:.6rem .75rem;border:2px solid #b5452a;border-radius:6px;background:#fff6f0}
.safety h3{margin:.1rem 0 .3rem;font-size:1rem;color:#8e2f17}
.safety ul{margin:.3rem 0;padding-left:1.2rem}
.safety li{margin:.2rem 0}
.ctl .btn[aria-pressed=true],.shiftbar .btn[aria-pressed=true]{background:var(--accent);color:#fff}
#flash{white-space:nowrap}
@media (max-width: 860px){ #flash{font-size:1.05rem;letter-spacing:.05em} }

/* pyramids of Giza additions */
#labels span.sec{background:rgba(255,253,247,.94);border-color:var(--ink)}
#labels span.fr{background:rgba(179,38,30,.92)}
#labels span.fe{background:rgba(201,110,25,.94)}
.shiftbar .range{display:inline-flex;align-items:center;gap:.4rem;flex:1 1 14rem;min-width:12rem}
.shiftbar .range input{flex:1;accent-color:var(--accent);height:1.6rem;min-width:6rem}
.shiftbar .range output{min-width:5.6rem;font-size:.9rem;text-align:left}
.shiftbar .range input:disabled{opacity:.45}
.chart svg text{font-family:system-ui,sans-serif}
@media (max-width: 860px){ .shiftbar .range{flex-basis:100%} }
/* FIG. 2 additions */
#sig-table tr.now th,#sig-table tr.now td{background:#fde7c4}

/* verdicts (FIG. 4) */
.persec dd.good { color: #2d6a2d; font-weight: 600; }
.persec dd.bad { color: #b0281a; font-weight: 600; }
.xsec { display: block; width: 150px; height: 150px; margin: 8px auto 4px; }
.key-c { color: #b03224; }
.key-t { color: #1f5fa8; }
@media (max-width: 860px){ #partinfo:not([hidden]) ~ .hint{visibility:hidden} }