/* Lambda Lab · Physics Hub (uses the Chemistry Hub design tokens from chemistry.css) */
:root{--gridc:rgba(100,116,139,.16);--tilebg:rgba(255,255,255,.78);--tilebrd:rgba(255,255,255,.95)}
:root[data-theme="dark"]{--gridc:rgba(148,163,184,.1);--tilebg:rgba(30,38,62,.8);--tilebrd:rgba(255,255,255,.08)}
/* ---------- home ---------- */
.phero{border-radius:var(--r-l);padding:24px 28px;display:flex;flex-wrap:wrap;gap:16px;justify-content:space-between;align-items:flex-end}
.phero h1{margin:0;font-size:42px;letter-spacing:-.03em;background:linear-gradient(90deg,#1d4ed8,#7c3aed 55%,#db2777);-webkit-background-clip:text;background-clip:text;color:transparent}
.phero p{margin:6px 0 0;color:var(--ink2);font-size:15.5px}
.phero-r{display:flex;flex-wrap:wrap;gap:10px;align-items:center}
.psearch{display:flex;align-items:center;gap:8px;padding:9px 14px;border-radius:999px;background:var(--glass2);border:1px solid var(--glass-brd);min-width:280px}
.psearch input{border:0;background:transparent;font:inherit;color:var(--ink);outline:none;flex:1}
.pcont{background:linear-gradient(135deg,rgba(34,197,94,.18),rgba(34,197,94,.08));font-weight:750;color:var(--ink)}
.pres{margin-top:12px;border-radius:20px;padding:12px;display:flex;flex-wrap:wrap;gap:8px}
.pcards{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:16px;margin-top:16px}
.pcard{position:relative;display:grid;align-content:start;text-align:start;border-radius:24px;padding:14px 16px;color:inherit;font:inherit;cursor:pointer;transition:transform .25s cubic-bezier(.2,.8,.2,1),box-shadow .25s}
.pcard:hover{transform:translateY(-4px);box-shadow:0 18px 40px rgba(47,84,235,.18)}
.pcard svg{width:100%;height:132px;margin:6px 0 2px}.pcard h3{margin:0;font-size:18px}.pcard p{margin:4px 0 0;font-size:12.5px;color:var(--ink2);line-height:1.45}
.pnum{justify-self:start;font-size:12px;font-weight:800;color:#2f54eb;background:#e8efff;padding:3px 9px;border-radius:8px}
.pcount{position:absolute;top:16px;inset-inline-end:16px;font-size:12px;color:var(--ink3);font-weight:700}
.pcard.soon{opacity:.72}.pcard.soon .pcount{background:rgba(148,163,184,.2);padding:2px 8px;border-radius:99px}
.popen{margin-top:10px;justify-self:start;font-weight:800;font-size:13px;color:#fff;background:linear-gradient(135deg,var(--accent),var(--accent2));padding:6px 14px;border-radius:999px}
:root[data-theme="dark"] .pnum{background:rgba(99,102,241,.22);color:#c7d2fe}
@media (max-width:1100px){.pcards{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media (max-width:640px){.pcards{grid-template-columns:1fr}.phero h1{font-size:32px}.psearch{min-width:0;flex:1}}
/* ---------- electricity lab layout ---------- */
.elab{display:grid;grid-template-columns:290px minmax(0,1fr) 320px;gap:14px;align-items:start}
.eside,.einfo{position:sticky;top:84px;max-height:calc(100vh - 100px);overflow:auto;scrollbar-width:thin}
.ecenter{border-radius:var(--r-l);padding:8px;display:grid;grid-template-rows:minmax(0,1fr) auto;height:calc(100vh - 110px);min-height:540px;min-width:0}
.ebench{position:relative;border-radius:20px;overflow:hidden;background:linear-gradient(180deg,#f8fafc,#e9eef6);touch-action:none}
:root[data-theme="dark"] .ebench{background:linear-gradient(180deg,#141a2e,#0d1222)}
.ebench svg{width:100%;height:100%;display:block;cursor:grab;user-select:none;-webkit-user-select:none}
.ebench svg:active{cursor:grabbing}
.ehint{position:absolute;left:12px;right:12px;bottom:10px;text-align:center;font-size:12px;color:var(--ink3);pointer-events:none}
.etools{display:flex;flex-wrap:wrap;align-items:center;gap:8px;padding:10px 6px 4px}.etools .btn{padding:8px 12px;font-size:13px}.esp{flex:1}
.ewc{display:flex;gap:6px}.ewc button{width:24px;height:24px;border-radius:50%;border:2px solid var(--glass2);background:var(--c);box-shadow:0 0 0 1px rgba(15,23,42,.15);cursor:pointer}.ewc button.on{box-shadow:0 0 0 3px var(--accent)}
/* parts on the bench */
.part{cursor:move}.part .tile{fill:var(--tilebg);stroke:var(--tilebrd);stroke-width:1.5;filter:url(#fSh)}.part .tile.ghost{fill:transparent;stroke:none;filter:none}
.part.sel .tile{stroke:var(--accent);stroke-width:3}.part.sel .tile.ghost{stroke:var(--accent);stroke-dasharray:8 6}
.part .term{cursor:crosshair}.part .term:hover circle:first-child{filter:brightness(1.2)}
.part .hole{fill:#57534e;stroke:#d6d3c8;stroke-width:2;cursor:crosshair}.part .hole:hover{fill:#22c55e}
.part .hit{cursor:pointer}.part text{user-select:none;pointer-events:none}
.part.dead .tile{stroke:#ef4444;stroke-dasharray:6 5}
.smoke{animation:smoke 1.6s ease-in-out infinite alternate}@keyframes smoke{to{transform:translateY(-8px);opacity:.6}}
.wire{cursor:pointer}.wire path{fill:none;stroke-linecap:round;stroke-linejoin:round}
.wsh{stroke:#0f172a;stroke-opacity:.16;stroke-width:12;transform:translateY(5px)}.wbody{stroke-width:8}.whl{stroke:#fff;stroke-opacity:.35;stroke-width:2;transform:translate(-1px,-2px)}
.whit{stroke:transparent;stroke-width:22}.wire.sel .wbody{stroke-width:10;filter:drop-shadow(0 0 6px rgba(99,102,241,.8))}
.wflow{stroke:#fde047;stroke-width:4;stroke-dasharray:0 26;animation:flow 1s linear infinite}@keyframes flow{from{stroke-dashoffset:26}to{stroke-dashoffset:0}}
@media (prefers-reduced-motion:reduce){.wflow{animation:none}.smoke{animation:none}}
/* side panels */
.elist{display:grid;gap:6px}.elist button{display:flex;gap:10px;align-items:center;text-align:start;padding:9px 10px;border-radius:14px;border:1px solid var(--glass-brd);background:var(--glass2);color:inherit;font:inherit;cursor:pointer}
.elist button i{flex:none;width:24px;height:24px;border-radius:50%;display:grid;place-items:center;font-style:normal;font-size:12px;font-weight:800;background:rgba(148,163,184,.25)}
.elist button span{display:grid}.elist button b{font-size:13.5px}.elist button small{font-size:11.5px;color:var(--ink3)}
.elist button.on{background:var(--accent);color:#fff;border-color:transparent;box-shadow:0 6px 16px rgba(79,70,229,.3)}.elist button.on small{color:rgba(255,255,255,.8)}.elist button.on i{background:rgba(255,255,255,.25)}
.estep{margin-top:12px;padding:14px;border-radius:18px;background:linear-gradient(160deg,#111827,#1e293b);color:#fff}
.estep small{font-size:11.5px;font-weight:800;letter-spacing:.07em;text-transform:uppercase;color:#86efac}.estep p{margin:6px 0 4px;font-size:14.5px;line-height:1.5}
.estep input{flex:1;min-width:0;border-radius:12px;border:0;padding:9px 12px;font:inherit}
.ehint2{background:none;border:0;color:#fde68a;font:inherit;font-size:13px;font-weight:700;cursor:pointer;padding:4px 0}.ehtxt{font-size:13px!important;color:#fde68a}
.equiz{display:grid;gap:6px;margin-top:8px}.equiz button{text-align:start;padding:9px 12px;border-radius:12px;border:0;background:rgba(255,255,255,.12);color:#fff;font:inherit;cursor:pointer}.equiz .ok{background:#16a34a}.equiz .bad{background:#dc2626}
.etg{margin:10px 0 6px;font-size:12px;font-weight:750;color:var(--ink2)}
.etray{display:grid;grid-template-columns:repeat(3,1fr);gap:6px}.etray button{display:grid;justify-items:center;gap:2px;padding:8px 4px 6px;border-radius:14px;border:1px solid var(--glass-brd);background:var(--glass2);color:inherit;font:inherit;cursor:grab;touch-action:none;transition:transform .15s}
.etray button:hover{transform:translateY(-2px)}.etray small{font-size:11px;font-weight:650;line-height:1.2;text-align:center}.eico{display:grid;place-items:center;height:48px}
.enote{font-size:12.5px;color:var(--ink3);line-height:1.5;margin:0}
.esel{padding:12px;border-radius:18px;background:var(--glass2);border:1px solid var(--glass-brd)}.esh{display:flex;gap:10px;align-items:center}.esh b{font-size:15px}.esh small{font-size:11px;color:var(--ink3);margin-inline-start:4px}.edead{display:block;color:#dc2626!important;font-weight:800}
.ekvs{display:grid;grid-template-columns:repeat(3,1fr);gap:6px;margin-top:10px}.ekv{display:grid;padding:7px 8px;border-radius:12px;background:rgba(148,163,184,.12)}.ekv span{font-size:10.5px;color:var(--ink3);font-weight:700}.ekv b{font-size:14px}
.erv{display:flex;gap:8px;align-items:center}.erv select{flex:1;padding:8px;border-radius:10px;border:1px solid var(--glass-brd);background:var(--glass2);color:var(--ink);font:inherit}
.ebands{display:flex;gap:2px;padding:5px 7px;border-radius:8px;background:#e8cf9e}.ebands i{width:5px;height:18px;border-radius:1px}
.seg.wrap{flex-wrap:wrap;border-radius:16px}.einfo input[type=range]{width:100%;accent-color:var(--accent)}
.emeters{display:grid;grid-template-columns:1fr 1fr;gap:6px}.emeter{display:grid;padding:8px 10px;border-radius:14px;background:var(--glass2);border:1px solid var(--glass-brd)}.emeter small{font-size:11px;font-weight:800;color:var(--ink3)}.emeter b{font-size:19px}.emeter b span{font-size:12px;color:var(--ink3)}
.etable{margin-top:8px;max-height:190px;overflow:auto;border-radius:12px;background:var(--glass2)}.etable table{width:100%;border-collapse:collapse;font-size:12px}.etable th,.etable td{padding:5px 6px;text-align:center;border-bottom:1px solid var(--glass-brd)}.etable th{position:sticky;top:0;background:var(--glass2)}
.eaxes{display:flex;gap:8px;margin-top:8px;font-size:12px;color:var(--ink3)}.eaxes select{margin-inline-start:4px;border-radius:8px;border:1px solid var(--glass-brd);background:var(--glass2);color:var(--ink);font:inherit;padding:3px}
.egraph{margin-top:6px;border-radius:14px;background:var(--glass2);padding:4px}.egraph svg{width:100%;display:block}
.einfo .row{display:flex;gap:6px;flex-wrap:wrap}.einfo .btn{padding:8px 12px;font-size:12.5px}
@media (max-width:1180px){.elab{grid-template-columns:260px minmax(0,1fr)}.einfo{grid-column:1/-1;position:static;max-height:none;display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:14px}}
@media (max-width:760px){.elab{grid-template-columns:1fr}.eside{position:static;max-height:none;order:2}.ecenter{order:1;height:62vh;min-height:420px}.einfo{order:3}.etray{grid-template-columns:repeat(4,1fr)}}
.lite .part .tile{filter:none}
:root[data-theme="dark"] .wsh{stroke:#cbd5e1;stroke-opacity:.28;stroke-width:11;transform:none}
@media (max-width:760px){.ehint{display:none}}
/* ---------- mechanics lab ---------- */
.mstagew{background:linear-gradient(180deg,#f8fafc,#e6ecf5)}:root[data-theme="dark"] .mstagew{background:linear-gradient(180deg,#1a2138,#0e1325)}
.mstagew svg{cursor:default}
.mctl{padding:10px 6px 4px;display:grid;gap:10px}.mcs{display:flex;flex-wrap:wrap;gap:10px 18px}
.mc{display:grid;gap:5px;min-width:180px;flex:1}.mcl{font-size:11px;font-weight:750;letter-spacing:.04em;text-transform:uppercase;color:var(--ink3)}
.mrow{display:flex;align-items:center;gap:8px}.mrow input{flex:1;accent-color:var(--accent);min-width:80px}.mrow b{min-width:66px;font-size:13.5px;text-align:end}
.mstep{width:28px;height:28px;border-radius:50%;border:1px solid var(--glass-brd);background:var(--glass2);font-weight:900;color:var(--accent);cursor:pointer}
.macts{display:flex;flex-wrap:wrap;gap:8px}.macts .btn{padding:9px 14px;font-size:13.5px}
.mfit{margin:6px 4px 2px;font-size:13px;color:var(--ink2)}
.mdel{border:0;background:none;color:var(--ink3);cursor:pointer;font-size:11px}
.mlab .ecenter{height:auto;min-height:0}.mlab .ebench{aspect-ratio:5/3;height:auto}
@media (max-width:760px){.mc{min-width:140px}.mlab .ecenter{height:auto}}

#mStage,#mStage text{direction:ltr;unicode-bidi:plaintext}
:root[data-theme="dark"] #mStage .mstr{stroke:#cbd5e1}
/* ---------- light & optics lab ---------- */
.otable{background:radial-gradient(120% 100% at 50% 40%,#161c2b,#070a12)!important}
.otable svg{cursor:grab}.otable .ehint{color:#94a3b8}
.obeams{mix-blend-mode:screen}
.opart{cursor:move}.opart .ohit{fill:transparent}.opart .osel{fill:none;stroke:#a5b4fc;stroke-width:1.4;stroke-dasharray:5 4}.opart path.osel{stroke-dasharray:none}
.opart .orot{fill:#6366f1;stroke:#fff;stroke-width:1.5;cursor:grab}
.oflame{transform-box:fill-box;transform-origin:50% 100%;animation:flick 1.3s ease-in-out infinite alternate}@keyframes flick{0%{transform:scale(1,1)}50%{transform:scale(.94,1.06) skewX(2deg)}100%{transform:scale(1.03,.96) skewX(-2deg)}}
.otray button .eico,.eico.odk{background:#0f1422;border-radius:10px;width:100%;height:50px}
.eico.odk{width:56px;height:46px}
.oview{border-radius:14px;overflow:hidden;background:var(--glass2);border:1px solid var(--glass-brd)}.oview svg{display:block;width:100%}.oview p{margin:0;padding:8px 10px;font-size:12.5px;color:var(--ink2)}
.emeter.otir{background:rgba(245,158,11,.18)}
@media (prefers-reduced-motion:reduce){.oflame{animation:none}}
.einfo .ctl-label b{text-transform:none;letter-spacing:0}.einfo .seg button{unicode-bidi:plaintext}
/* ---- Waves & Sound lab */
.wstage{aspect-ratio:5/3}.wstage canvas,.wstage svg{position:absolute;inset:0;width:100%;height:100%}
.wstage canvas{display:none}.wstage.dark canvas{display:block}.wstage.dark{background:#0b1a2a}
.wstage svg{cursor:default}.wstage svg:focus-visible{outline:3px solid var(--accent);outline-offset:-3px}
#wSvg,#wSvg text{direction:ltr;unicode-bidi:plaintext}.wstage .wmk{cursor:ew-resize}
.wsnd.on{background:var(--accent);color:#fff}.wmkn{margin:0;font-size:12px}
:root[data-theme="dark"] #wSvg .mstr{stroke:#cbd5e1}
.wlab .eaxes label{flex:1 1 0;min-width:0;display:flex;flex-direction:column;gap:2px}.wlab .eaxes select{max-width:100%;margin-inline-start:0}
.wsnd:disabled{opacity:.6;cursor:not-allowed}
/* ---- Heat lab */
.hlab .hst{font-size:14px;font-weight:800}
@media (max-width:560px){.hlab .mc{flex-basis:100%}.hlab .mrow input[type=range]{min-width:0;flex:1}}
/* ---- Magnetism + Matter labs */
.glab .wstage svg .drg:active{cursor:grabbing}
/* ---- Physics games */
.gmiss{display:inline-block;min-width:1.6em;padding:0 .2em;border-radius:8px;background:var(--accent);color:#fff}
/* ---- answer boxes (labs + games): always dark text on a white field, in every theme */
.estep input,.gbody input:not([type=range]){background:#fff;color:#0f172a;-webkit-text-fill-color:#0f172a;caret-color:#4f46e5;border:1.5px solid #cbd5e1;border-radius:12px;padding:9px 12px;font-weight:700;opacity:1}
.estep input::placeholder,.gbody input:not([type=range])::placeholder{color:#64748b;-webkit-text-fill-color:#64748b;font-weight:500}
.gbody input:not([type=range]):disabled{background:#e2e8f0;color:#334155;-webkit-text-fill-color:#334155}
/* ---- Lab report + CSV */
.lrbar{display:flex;gap:8px;flex-wrap:wrap;margin-top:8px}.lrbar .btn{padding:7px 12px;font-size:13px}
.lr{position:fixed;inset:0;z-index:200;overflow:auto;background:rgba(15,23,42,.55);backdrop-filter:blur(6px);-webkit-backdrop-filter:blur(6px);padding:18px 12px 40px}
.lr-bar{position:sticky;top:0;z-index:2;display:flex;flex-wrap:wrap;align-items:center;gap:10px;max-width:820px;margin:0 auto 14px;padding:10px 12px;border-radius:16px;background:rgba(255,255,255,.92);box-shadow:0 10px 30px rgba(0,0,0,.2)}
.lr-tip{flex:1;min-width:160px;font-size:12px;color:#475569}
.lr-page{--ink:#0f172a;--ink2:#334155;--ink3:#64748b;--accent:#4f46e5;--glass2:#f8fafc;--glass-brd:#e2e8f0;max-width:820px;margin:0 auto;background:#fff;color:#0f172a;border-radius:14px;padding:44px 52px;box-shadow:0 20px 60px rgba(0,0,0,.3);font-size:14.5px;line-height:1.6}
.lr-head{display:flex;justify-content:space-between;gap:12px;font-size:12px;color:#64748b;border-bottom:2px solid #e2e8f0;padding-bottom:10px}.lr-brand{font-weight:800;color:#4f46e5}
.lr-page h1{font-size:28px;margin:18px 0 2px;letter-spacing:-.5px}.lr-kind{margin:0 0 16px;color:#64748b;font-size:13px}
.lr-page h2{font-size:17px;margin:22px 0 8px;color:#1e3a8a;border-bottom:1px solid #e2e8f0;padding-bottom:4px}.lr-page h3{font-size:14px;margin:14px 0 6px;color:#334155}
.lr-fields{display:flex;gap:18px;flex-wrap:wrap}.lr-fields label{display:flex;align-items:flex-end;gap:8px;font-weight:700;flex:1;min-width:200px}
.lr-in{flex:1;min-width:120px;display:inline-block;border-bottom:1.5px dotted #94a3b8;min-height:1.5em;outline:none;padding:0 4px;color:#1e40af}.lr-in.wide{min-width:60%}
.lr-in:focus,.lr-concl:focus{background:#eef2ff}
.lr-steps{padding-inline-start:22px;margin:0}.lr-steps li{margin:4px 0}
.lr-table{border-collapse:collapse;width:100%;font-size:13px}.lr-table th,.lr-table td{border:1px solid #cbd5e1;padding:5px 8px;text-align:center}.lr-table th{background:#f1f5f9}
.lr-small{font-size:12px;color:#64748b}.lr-empty{color:#94a3b8;font-style:italic}
.lr-graph{max-width:520px;margin:0 auto;border:1px solid #e2e8f0;border-radius:10px;padding:8px}.lr-graph svg{width:100%;height:auto;display:block}
.lr-fit{text-align:center;font-size:13.5px}.lr-box{margin-top:12px;padding:10px 12px;border:1.5px solid #c7d2fe;border-radius:10px;background:#f8faff;display:flex;gap:8px;align-items:flex-end}
.lr-concl{min-height:110px;padding:8px 10px;border-radius:8px;outline:none;background:repeating-linear-gradient(#fff 0 27px,#cbd5e1 27px 28px);line-height:28px;color:#1e40af}
.lr-concl:empty::before{content:attr(data-ph);color:#94a3b8}
.lr-foot{margin-top:26px;padding-top:10px;border-top:1px solid #e2e8f0;font-size:11px;color:#94a3b8;text-align:center}
@media (max-width:640px){.lr-page{padding:26px 18px}.lr-page h1{font-size:22px}}
@media print{html.lr-open body>*:not(#labReport){display:none!important}html.lr-open #labReport{display:block!important}html.lr-open,html.lr-open body{background:#fff!important}
 .lr{position:static;background:none;padding:0;overflow:visible;backdrop-filter:none}.lr-bar{display:none}.lr-page{box-shadow:none;border-radius:0;max-width:none;padding:0}
 .lr-concl{background:repeating-linear-gradient(#fff 0 27px,#94a3b8 27px 28px)}.lr-concl:empty::before{content:''}.lr-in:empty{min-width:160px}.lr-table tr,.lr-graph{break-inside:avoid}
 @page{size:A4;margin:12mm 13mm}}
/* ---- Worksheets */
.ps-hero .row{align-items:center;gap:10px}
.ps-wrap{display:grid;grid-template-columns:300px minmax(0,1fr);gap:18px;align-items:start;margin-top:16px}
.ps-side{position:sticky;top:90px;max-height:calc(100vh - 110px);overflow:auto;display:grid;gap:10px}
.ps-sec{border-radius:12px;background:var(--glass2);padding:6px 10px}.ps-sec summary{cursor:pointer;display:flex;justify-content:space-between;align-items:center;padding:4px 0;font-size:14px}.ps-sec summary small{color:var(--ink3)}
.ps-item{display:flex;gap:8px;align-items:flex-start;padding:5px 2px;font-size:13px;cursor:pointer}.ps-item input{margin-top:3px;accent-color:var(--accent)}
.ps-pages{display:grid;gap:22px;justify-items:center}.ps-empty{padding:40px 10px;text-align:center}
.ps-page{width:100%;max-width:800px;background:#fff;color:#0f172a;border-radius:12px;padding:40px 48px;box-shadow:0 14px 40px rgba(15,23,42,.18);font-size:13.5px;line-height:1.55}
.ps-head{display:flex;justify-content:space-between;gap:12px;font-size:11.5px;color:#64748b;border-bottom:2px solid #e2e8f0;padding-bottom:8px}.ps-brand{font-weight:800;color:#4f46e5}
.ps-page h1{font-size:24px;margin:14px 0 8px}.ps-page h2{font-size:15px;margin:16px 0 6px;color:#1e3a8a;border-bottom:1px solid #e2e8f0;padding-bottom:3px}.ps-page h3{font-size:13.5px;margin:12px 0 4px}
.ps-fields{display:flex;gap:14px;flex-wrap:wrap;font-weight:700}.ps-fields span{display:flex;gap:6px;flex:1;min-width:150px}.ps-fields i{flex:1;border-bottom:1.5px dotted #94a3b8}
.ps-steps,.ps-qs{padding-inline-start:22px;margin:0}.ps-steps li,.ps-qs>li{margin:4px 0}
.ps-table{border-collapse:collapse;width:100%;font-size:12.5px;margin-top:6px}.ps-table th,.ps-table td{border:1px solid #94a3b8;padding:4px 6px;text-align:center;height:24px}.ps-table th{background:#f1f5f9}.ps-table td:first-child{width:28px;color:#94a3b8}
.ps-grid{width:100%;max-width:560px;display:block;margin:4px auto}.ps-note{font-size:12px;color:#475569;margin:2px 0}
.ps-line{margin:6px 0 10px;border-bottom:1.5px dotted #94a3b8;height:22px;color:#64748b;font-size:12px}
.ps-mc{margin:4px 0 8px;padding-inline-start:22px}.ps-foot{margin-top:18px;padding-top:8px;border-top:1px solid #e2e8f0;font-size:10.5px;color:#94a3b8;text-align:center}
.ps-key h3{margin-top:14px;color:#1e3a8a}
@media (max-width:900px){.ps-wrap{grid-template-columns:1fr}.ps-side{position:static;max-height:none}.ps-page{padding:24px 18px}}
#psPrintCopy{display:none}
@media print{html.ps-printing body>*:not(#psPrintCopy){display:none!important}html.ps-printing,html.ps-printing body{background:#fff!important}
 html.ps-printing #psPrintCopy{display:block!important}
 html.ps-printing .ps-page{box-shadow:none;border-radius:0;max-width:none;padding:0;break-after:page}html.ps-printing .ps-page:last-child{break-after:auto}
 .ps-table tr,.ps-qs>li,.ps-grid{break-inside:avoid}
 html.ps-printing .ps-page{font-size:11.5px;line-height:1.38}html.ps-printing .ps-page h1{font-size:20px;margin:10px 0 6px}html.ps-printing .ps-page h2{font-size:13.5px;margin:10px 0 4px}
 html.ps-printing .ps-table{font-size:11.5px}html.ps-printing .ps-table th,html.ps-printing .ps-table td{height:18px;padding:1px 5px}html.ps-printing .ps-grid{max-width:430px}
 html.ps-printing .ps-foot{margin-top:8px;padding-top:5px}html.ps-printing .ps-grid{max-width:300px;margin:0 auto}
 html.ps-printing .ps-duo{display:grid;grid-template-columns:minmax(0,.9fr) minmax(0,1.1fr);gap:20px;align-items:start}html.ps-printing .ps-duo>:only-child{grid-column:1/-1}html.ps-printing .ps-duo .ps-grid{max-width:100%}html.ps-printing .ps-duo h2{margin-top:12px}
 html.ps-printing .ps-mc{display:flex;flex-wrap:wrap;gap:2px 26px;list-style-position:inside;padding-inline-start:4px;margin:2px 0 6px}html.ps-printing .ps-mc li{display:list-item}}
/* ---- the hub nav has 12 entries: tighter spacing so it fits on laptop screens */
#hubNav button{padding:7px 8px;font-size:13px}
@media (min-width:901px) and (max-width:1380px){#hubNav button{padding:6px 5px;font-size:12px}}
@media (min-width:901px) and (max-width:1180px){#hubNav button{padding:5px 5px;font-size:12px}}
#hubNav.ovf{-webkit-mask-image:linear-gradient(90deg,transparent 0,#000 16px,#000 calc(100% - 26px),transparent);mask-image:linear-gradient(90deg,transparent 0,#000 16px,#000 calc(100% - 26px),transparent)}
@media (max-width:560px){.mlab .mc{flex-basis:100%}.mlab .mrow input[type=range]{min-width:0;flex:1}}
.eaxes label{min-width:0}.eaxes select{max-width:100%;min-width:0}
/* ---- Toolbox: formulas, constants, converter, glossary, progress, certificate */
.pt-tabs{display:flex;flex-wrap:wrap;gap:4px;margin:16px 0 12px;padding:5px;border-radius:16px;width:max-content;max-width:100%}
.pt-tabs button{padding:9px 16px;font-weight:750}
.pt-bar{display:flex;flex-wrap:wrap;gap:10px;align-items:center;margin-bottom:10px}.pt-search{flex:1;min-width:200px;max-width:460px}
.pt-chips{margin:0 0 14px;flex-wrap:wrap}
.pt-h{font-size:17px;margin:18px 0 10px;color:var(--ink2)}
.pt-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:12px}
.pt-f{border-radius:16px;padding:14px 16px;background:var(--glass2);border:1px solid var(--glass-brd);display:flex;flex-direction:column;gap:6px}
.pt-fq{font-family:'Cambria Math','STIX Two Math','Times New Roman',serif;font-size:22px;font-weight:700;color:var(--ink);padding:8px 10px;border-radius:10px;background:linear-gradient(135deg,rgba(99,102,241,.1),rgba(34,211,238,.1));text-align:center}
.pt-f h3{margin:4px 0 0;font-size:14.5px}.pt-f ul{margin:0;padding-inline-start:18px;font-size:12.5px;color:var(--ink2);line-height:1.55}.pt-f ul b{font-family:'Times New Roman',serif;font-size:14px}
.pt-try{align-self:flex-start;margin-top:auto;font-size:12.5px;padding:6px 10px}
.pt-table td,.pt-table th{padding:8px 10px;text-align:start}.pt-table td:first-child{font-family:'Times New Roman',serif;font-size:16px}.pt-table{max-height:none}
.pt-conv{display:flex;flex-wrap:wrap;gap:12px;align-items:flex-end;padding:16px;border-radius:18px}.pt-conv label{display:grid;gap:4px;font-size:12px;font-weight:750;color:var(--ink3);flex:1;min-width:160px}
.pt-conv input,.pt-conv select{font:inherit;font-size:16px;padding:9px 10px;border-radius:10px;border:1px solid var(--glass-brd);background:var(--glass2);color:var(--ink)}
.pt-res{font-size:24px;margin:16px 4px;color:var(--ink2)}.pt-res b{color:var(--accent);font-size:30px}
.pt-allu{display:grid;grid-template-columns:repeat(auto-fill,minmax(200px,1fr));gap:8px}.pt-allu div{padding:10px 12px;border-radius:12px;background:var(--glass2);border:1px solid var(--glass-brd);display:grid}.pt-allu div.on{border-color:var(--accent)}
.pt-allu b{font-size:16px}.pt-allu span{font-weight:800;color:var(--accent)}.pt-allu small{color:var(--ink3)}
.pt-gl{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:12px}
.pt-term{padding:14px 16px;border-radius:16px;background:var(--glass2);border:1px solid var(--glass-brd)}.pt-term h3{margin:0;font-size:17px}.pt-term p{margin:6px 0;font-size:13.5px;line-height:1.55;color:var(--ink2)}.pt-term small{color:var(--ink3);font-size:11px}
.pt-alt{display:flex;flex-wrap:wrap;gap:6px 14px}.pt-alt span{font-size:12.5px;color:var(--ink2)}.pt-alt i{font-style:normal;font-weight:900;font-size:10px;padding:1px 5px;border-radius:5px;background:rgba(99,102,241,.14);color:#4f46e5;margin-inline-end:3px}
.pt-prog{display:flex;flex-wrap:wrap;gap:20px;align-items:center;padding:18px 22px;border-radius:20px}.pt-ring{width:150px;height:150px}.pt-prog-r{flex:1;min-width:240px}.pt-prog-r h2{margin:0 0 6px}
.pt-lv{display:inline-block;padding:5px 12px;border-radius:999px;font-weight:850;background:var(--lb);color:var(--lc);border:1px solid var(--lc)}
.pt-name{display:grid;gap:4px;font-size:12px;font-weight:750;color:var(--ink3);max-width:360px;margin-top:8px}.pt-name input{font:inherit;font-size:16px;padding:9px 12px;border-radius:10px;border:1px solid var(--glass-brd);background:var(--glass2);color:var(--ink)}
.pt-secs{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:12px;margin-top:14px}.pt-sec{padding:14px 16px;border-radius:18px}.pt-sec header{display:flex;justify-content:space-between;font-size:14.5px}
.pt-barx{height:8px;border-radius:99px;background:var(--glass-brd);margin:8px 0 10px;overflow:hidden}.pt-barx i{display:block;height:100%;border-radius:99px;background:linear-gradient(90deg,#22d3ee,#7c3aed)}
.pt-exps{display:flex;flex-wrap:wrap;gap:6px}.pt-exps .chip{font-size:12px}.pt-badges{display:flex;flex-wrap:wrap;gap:8px}
.pt-certwrap{overflow-x:auto;padding:6px 2px}
.pt-cert{-webkit-print-color-adjust:exact;print-color-adjust:exact;width:900px;max-width:100%;aspect-ratio:297/210;background:#fffdf7;color:#1f2937;border-radius:8px;padding:18px;box-shadow:0 16px 40px rgba(15,23,42,.18);font-family:Georgia,'Times New Roman',serif;box-sizing:border-box}
.pt-cert-in{height:100%;box-sizing:border-box;border:3px double var(--lc);outline:10px solid var(--lb);outline-offset:-16px;padding:34px 48px;display:flex;flex-direction:column;align-items:center;text-align:center;gap:6px;
 background:radial-gradient(circle at 0 0,var(--lb) 0 60px,transparent 61px),radial-gradient(circle at 100% 0,var(--lb) 0 60px,transparent 61px),radial-gradient(circle at 0 100%,var(--lb) 0 60px,transparent 61px),radial-gradient(circle at 100% 100%,var(--lb) 0 60px,transparent 61px)}
.pt-cert-top{display:flex;gap:10px;align-items:center;font:700 14px system-ui,sans-serif;letter-spacing:.08em;text-transform:uppercase;color:#475569}.pt-cert-logo{width:34px;height:34px;border-radius:10px;display:grid;place-items:center;background:linear-gradient(135deg,#22d3ee,#7c3aed);color:#fff;font-size:20px}
.pt-cert h1{margin:auto 0 2px;font-size:44px;color:var(--lc);letter-spacing:.01em}.pt-cert-this{margin:6px 0 0;font-size:16px;color:#475569;font-style:italic}
.pt-cert-name{margin:4px 0;font-size:40px;font-weight:700;color:#111827;border-bottom:2px solid var(--lc);padding:0 30px 4px;min-width:50%}
.pt-cert-did{margin:6px 0;font-size:16px;max-width:80%;line-height:1.5}.pt-cert-secs{display:flex;flex-wrap:wrap;justify-content:center;gap:6px;max-width:90%}.pt-cert-secs span{font:600 11.5px system-ui,sans-serif;padding:3px 9px;border-radius:99px;background:var(--lb);color:#334155}
.pt-cert-foot{margin-top:auto;width:100%;display:flex;justify-content:space-between;align-items:flex-end}.pt-cert-foot>div{display:grid;gap:2px;min-width:170px}.pt-cert-foot small{font:600 11px system-ui,sans-serif;color:#64748b}.pt-cert-foot b{font-size:15px;border-top:1px solid #94a3b8;padding-top:4px}
.pt-sign{font-style:italic}.pt-medal{justify-items:center}.pt-medal span{width:64px;height:64px;border-radius:50%;display:grid;place-items:center;font-size:30px;color:#fff;background:radial-gradient(circle at 35% 30%,#fff8,transparent 45%),var(--lc);box-shadow:0 0 0 5px var(--lb),0 0 0 7px var(--lc)}.pt-medal b{border:0!important;font:800 12px system-ui,sans-serif;color:var(--lc)}
@media (max-width:640px){.pt-cert h1{font-size:26px}.pt-cert-name{font-size:24px}.pt-cert-in{padding:18px}.pt-cert-did{font-size:12px}.pt-cert-foot>div{min-width:0}.pt-medal span{width:40px;height:40px;font-size:18px}.pt-res{font-size:18px}.pt-res b{font-size:22px}}
#ptPrint{display:none}
@media print{html.pt-printing body>*:not(#ptPrint){display:none!important}html.pt-printing #ptPrint{display:block!important}html.pt-printing,html.pt-printing body{background:#fff!important}
 #ptPrint .pt-sheet h1{font-size:20px;margin:0 0 8px}#ptPrint .pt-grid{grid-template-columns:repeat(4,1fr);gap:6px}#ptPrint .pt-f{break-inside:avoid;background:#fff;border:1px solid #cbd5e1;color:#0f172a;padding:8px 10px}#ptPrint .pt-fq{font-size:14px;padding:4px;background:#f1f5f9;color:#0f172a}#ptPrint .pt-f h3{font-size:11.5px}#ptPrint .pt-f ul{color:#334155;font-size:10.5px}#ptPrint .pt-h{color:#1e3a8a;font-size:14px;margin:10px 0 6px;break-after:avoid}
 #ptPrint.cert{page:cert}#ptPrint.cert .pt-cert{width:297mm;height:210mm;max-width:none;aspect-ratio:auto;border-radius:0;box-shadow:none;padding:10mm}
 @page cert{size:A4 landscape;margin:0}}
/* ---- Exam mode */
.px-setup,.px-best{margin-top:16px;padding:18px 22px;border-radius:20px}.px-setup .chips{flex-wrap:wrap}.px-setup .chip small{font-weight:800;color:var(--accent);margin-inline-start:4px}
.px-go{margin:12px 0 6px;font-size:16px;padding:12px 22px}
.px-bests{display:grid;grid-template-columns:repeat(auto-fill,minmax(190px,1fr));gap:8px}.px-bests div{display:flex;justify-content:space-between;gap:8px;padding:8px 12px;border-radius:12px;background:var(--glass2);border:1px solid var(--glass-brd);font-size:13px}.px-bests b{color:var(--accent)}
.px-run{max-width:860px;margin:18px auto 0;padding:20px 24px;border-radius:22px}.px-top{display:flex;justify-content:space-between;align-items:center;gap:10px}
.px-clock{font:800 22px 'Courier New',monospace;color:var(--ink)}.px-time{height:8px;border-radius:99px;background:var(--glass-brd);overflow:hidden;margin:8px 0 12px}.px-time i{display:block;height:100%;width:100%;background:linear-gradient(90deg,#22c55e,#06b6d4);transition:width .25s linear}.px-time i.low{background:linear-gradient(90deg,#ef4444,#f59e0b)}
.px-dots{display:flex;flex-wrap:wrap;gap:5px}.px-dots button{width:30px;height:30px;border-radius:9px;border:1px solid var(--glass-brd);background:var(--glass2);font-weight:800;font-size:12px;color:var(--ink2)}.px-dots .done{background:rgba(99,102,241,.18);color:#4f46e5}.px-dots .cur{outline:2.5px solid var(--accent);outline-offset:1px}
.px-q{font-size:21px;line-height:1.45;margin:18px 0 14px}.px-opts{display:grid;gap:10px}
.px-opt{display:flex;gap:12px;align-items:center;text-align:start;padding:13px 16px;border-radius:14px;border:1.5px solid var(--glass-brd);background:var(--glass2);font-size:15.5px;font-weight:600;color:var(--ink)}
.px-opt span{width:28px;height:28px;flex:none;border-radius:8px;display:grid;place-items:center;background:rgba(99,102,241,.14);color:#4f46e5;font-weight:900;font-size:13px}.px-opt:hover{border-color:var(--accent)}.px-opt.on{border-color:var(--accent);background:rgba(99,102,241,.14)}.px-opt.on span{background:var(--accent);color:#fff}
.px-nav{margin-top:16px;flex-wrap:wrap;align-items:center}.px-nav .enote{flex:1;text-align:center}
.px-res{margin-top:18px;padding:22px 26px;border-radius:22px;display:flex;flex-wrap:wrap;gap:24px;align-items:center}.px-res h2{margin:0 0 6px;font-size:28px}
.px-score{width:150px;height:150px;border-radius:50%;display:grid;place-content:center;text-align:center;background:radial-gradient(closest-side,var(--glass2) 78%,transparent 79% 100%),conic-gradient(#7c3aed calc(var(--p)*1%),var(--glass-brd) 0)}.px-score b{font-size:32px}.px-score span{font-weight:800;color:var(--ink3)}
.px-new{font-weight:800;color:#b45309}.px-rev{display:grid;gap:10px}.px-ri{padding:12px 16px;border-radius:14px;background:var(--glass2);border:1px solid var(--glass-brd);border-inline-start:5px solid #22c55e}.px-ri.bad{border-inline-start-color:#ef4444}
.px-ri p{margin:4px 0}.px-a{font-size:13.5px;color:#15803d}.px-a.bad{color:#b91c1c}.lxbar{margin-top:10px;width:100%;justify-content:center}
@media (max-width:640px){.px-run{padding:16px}.px-q{font-size:18px}.px-score{width:120px;height:120px}}
/* worksheets: random practice calculations, copies */
.ps-calc{margin:0;padding:0;list-style-position:inside;display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:6px 16px}.ps-calc>li{margin:2px 0;font-size:.95em;line-height:1.45}.ps-calc .ps-line{margin-top:8px}
.ps-num{width:70px;font:inherit;padding:6px 8px;border-radius:10px;border:1px solid var(--glass-brd);background:var(--glass2);color:var(--ink)}
.ps-kcopy{margin:18px 0 6px;padding-top:8px;border-top:2px solid #e2e8f0;color:#7c3aed}
@media (max-width:760px){.ps-calc{grid-template-columns:1fr}}
@media print{html.ps-printing .ps-calc{grid-template-columns:repeat(3,minmax(0,1fr))}html.ps-printing .ps-calc>li{font-size:11px;break-inside:avoid}html.ps-printing .ps-kcopy{break-before:page}html.ps-printing .ps-key .ps-kcopy:first-of-type{break-before:auto}}

/* worksheets: the same print layout, used off-screen to measure each page and shrink the few that would not fit on one A4 page */
#psPrintCopy.measure{display:block!important;position:absolute;left:-99999px;top:0;width:184mm;visibility:hidden}
#psPrintCopy.measure .ps-page{box-shadow:none;border-radius:0;max-width:none;padding:0;}#psPrintCopy.measure .ps-page{font-size:11.5px;line-height:1.38}#psPrintCopy.measure .ps-page h1{font-size:20px;margin:10px 0 6px}#psPrintCopy.measure .ps-page h2{font-size:13.5px;margin:10px 0 4px}#psPrintCopy.measure .ps-table{font-size:11.5px}#psPrintCopy.measure .ps-table th,#psPrintCopy.measure .ps-table td{height:18px;padding:1px 5px}#psPrintCopy.measure .ps-grid{max-width:430px}#psPrintCopy.measure .ps-foot{margin-top:8px;padding-top:5px}#psPrintCopy.measure .ps-grid{max-width:300px;margin:0 auto}#psPrintCopy.measure .ps-duo{display:grid;grid-template-columns:minmax(0,.9fr) minmax(0,1.1fr);gap:20px;align-items:start}#psPrintCopy.measure .ps-duo>:only-child{grid-column:1/-1}#psPrintCopy.measure .ps-duo .ps-grid{max-width:100%}#psPrintCopy.measure .ps-duo h2{margin-top:12px}#psPrintCopy.measure .ps-mc{display:flex;flex-wrap:wrap;gap:2px 26px;list-style-position:inside;padding-inline-start:4px;margin:2px 0 6px}#psPrintCopy.measure .ps-mc li{display:list-item}#psPrintCopy.measure .ps-calc{grid-template-columns:repeat(3,minmax(0,1fr))}#psPrintCopy.measure .ps-calc>li{font-size:11px;break-inside:avoid}
/* ---- optional difficulty levels */
.lvb{display:inline-flex;align-items:center;gap:4px;font-size:10.5px;font-weight:800;padding:1px 7px;border-radius:999px;vertical-align:middle;white-space:nowrap;margin-inline-start:4px}
.lvb i{font-style:normal;letter-spacing:1px;font-size:8px}
.lvb.lv1{background:rgba(34,197,94,.14);color:#15803d}.lvb.lv2{background:rgba(245,158,11,.16);color:#b45309}.lvb.lv3{background:rgba(168,85,247,.15);color:#7e22ce}
:root[data-theme="dark"] .lvb.lv1{color:#86efac}:root[data-theme="dark"] .lvb.lv2{color:#fcd34d}:root[data-theme="dark"] .lvb.lv3{color:#d8b4fe}
.elist button .lvb{margin-top:3px}.plv{margin:12px 0 0}.plv .chip .lvb{margin:0}.ps-lv{margin:6px 0 8px;flex-wrap:wrap}.ps-lv .chip .lvb{margin:0}
.plvnote{margin:4px 2px 0;font-size:11.5px;line-height:1.45;color:var(--ink3);max-width:280px}
.elist button.on .lvb{background:rgba(255,255,255,.22);color:#fff}
/* links from a lab to the matching 3D lessons of the main site */
.l3d{margin-top:10px;display:grid;gap:6px;padding:10px;border-radius:14px;border:1px solid var(--glass-brd);background:var(--glass2)}
.l3d-h{font-size:12px;font-weight:800;color:var(--ink2)}
.l3d-a{display:flex;justify-content:space-between;gap:8px;align-items:center;padding:7px 10px;border-radius:10px;font-size:13px;font-weight:650;text-decoration:none;color:var(--accent);background:rgba(99,102,241,.08)}
.l3d-a:hover{background:rgba(99,102,241,.16)}.l3d-a:focus-visible{outline:2px solid var(--accent);outline-offset:2px}
@media print{.l3d{display:none!important}}
.psearch input{min-width:0;width:100%}
.pcard svg{direction:ltr}
/* games: long story answers, graph thumbnails and the cannon controls */
.gopts .glong{display:block;font-size:15px;font-weight:600;line-height:1.35}
.gopts button svg{pointer-events:none}
.gcctl{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:10px 18px;align-items:end;margin-top:12px}
.gcctl label{display:grid;gap:6px;font-size:13px;font-weight:700;color:var(--ink2)}.gcctl label b{color:var(--accent)}.gcctl input[type=range]{width:100%}
.gcctl .row{gap:10px;align-items:center}.gcctl .enote{margin:0}
/* cross-hub phase B · the labs with a 1000 × 600 picture (phys-stage.js). A strip of squared paper is always kept above the
   drawing for the full-screen button (the drawing sits at the bottom of its box: the bench stays on the floor). On computers
   the middle column reaches the bottom of the window, like the list of labs beside it: the picture box grows taller. */
.ecenter.ptall{container-type:inline-size}
.ecenter.ptall>.ebench{aspect-ratio:auto;height:calc(60cqw + 44px)}
.ecenter.ptall .wstage canvas{object-fit:contain;object-position:50% 100%}
@media (min-width:901px){.ecenter.ptall:not(.qfs-on){height:auto;min-height:calc(100vh - 100px);display:flex;flex-direction:column}
 .ecenter.ptall:not(.qfs-on)>.ebench{flex:1 0 auto}.ecenter.ptall:not(.qfs-on)>.mctl{flex:none}}
/* full screen: the picture takes the room the controls leave (phys-stage.js keeps it at 5 : 3 plus the strip); the free workbench
   and the free optical table simply fill the screen */
.ecenter.ptall.qfs-on,.ecenter.pfs.qfs-on{width:100vw;height:100vh;max-width:none;min-height:0;margin:0;border-radius:0;padding:12px;box-sizing:border-box;background:var(--bg);overflow:auto}
.ecenter.ptall.qfs-on{display:flex;flex-direction:column;gap:6px}
.ecenter.ptall.qfs-on>.ebench{flex:1 1 0;height:auto;min-height:min(45vh,300px);width:100%;align-self:center}
.ecenter.ptall.qfs-on>.mctl{flex:0 1 auto;min-height:0;overflow:auto;width:100%}
@media (min-width:901px){.ecenter.pfs:not(.qfs-on){height:calc(100vh - 100px)}}