/* F to A Learning Lab · AS Biology 9700 Topic 8 · one design system, no external dependencies */
:root{
  --orange:#EF7D1A; --orange-ink:#9A4300; --orange-soft:#FDF2E7; --orange-line:#F2C9A2;
  --blue:#0B5C9E; --blue-2:#1E6FB8; --blue-soft:#EDF4FA; --blue-line:#BFD5EA;
  --ink:#14171A; --ink-2:#3A4047; --muted:#5A6169; --g1:#F6F7F8; --g2:#ECEEF0; --g3:#D5D9DD; --g4:#6B7480;
  --bg:#F6F7F8; --card:#fff; --line:#DDE1E5;
  --ok:#17703A; --ok-soft:#E8F4EC; --ok-line:#A8D5B7; --bad:#B42318; --bad-soft:#FCEDEB; --bad-line:#EFB3AC;
  --oxy:#B3261E; --deoxy:#3F5F95; --radius:12px;
  --font:Inter,system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  color-scheme: light;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-padding-top:120px}
body{margin:0;font-family:var(--font);font-size:16px;line-height:1.55;color:var(--ink);background:var(--bg);overflow-x:hidden}
a{color:var(--blue)}
h1,h2,h3,h4{line-height:1.25;margin:0 0 .5rem;letter-spacing:-.01em}
h1{font-size:1.6rem;font-weight:750} h2{font-size:1.15rem;font-weight:700} h3{font-size:1.02rem;font-weight:700} h4{font-size:.95rem;margin:.2rem 0 .4rem}
p{margin:.4rem 0 .75rem}
:focus-visible{outline:3px solid var(--blue-2);outline-offset:2px;border-radius:6px}
.skip{position:absolute;left:-999px;top:0;background:var(--ink);color:#fff;padding:.7rem 1rem;z-index:99;border-radius:0 0 8px 0}
.skip:focus{left:0;top:0}
.sr{position:absolute!important;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
.nw{white-space:nowrap}

/* ---------- header and navigation ---------- */
header.top{position:sticky;top:0;z-index:20;background:#fff;border-bottom:1px solid var(--line)}
.brandbar{display:flex;align-items:center;gap:.65rem;padding:.45rem 1rem .2rem;max-width:1240px;margin:0 auto}
.brandbar img{width:36px;height:36px;flex:none;display:block}
.brandtxt{display:flex;flex-direction:column;min-width:0;line-height:1.2}
.brandtxt .wm{font-size:1.02rem;font-weight:800;letter-spacing:.04em;white-space:nowrap;color:var(--ink)}
.brandtxt .wm .fa{color:#F15A24;background:linear-gradient(90deg,#F7931E,#F15A24);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.brandtxt .wm .ll{color:var(--blue);font-weight:700}
.brandtxt small{font-size:.8rem;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.brandbar .sp{flex:1}
.brandbar .prog{font-size:.8rem;color:var(--muted);white-space:nowrap}
nav.tabs{max-width:1240px;margin:0 auto;display:flex;gap:.1rem;overflow-x:auto;padding:0 .6rem;scrollbar-width:none}
nav.tabs::-webkit-scrollbar{display:none}
nav.tabs a{flex:none;text-decoration:none;color:var(--ink-2);padding:0 .7rem;font-size:.92rem;font-weight:600;min-height:46px;display:inline-flex;align-items:center;gap:.35rem;white-space:nowrap;border-bottom:3px solid transparent}
nav.tabs a:hover{color:var(--ink);border-bottom-color:var(--g3)}
nav.tabs a .num{font-size:.75rem;color:var(--muted);font-weight:700;font-variant-numeric:tabular-nums}
nav.tabs a[aria-current="page"]{color:var(--ink);border-bottom-color:var(--orange)}
nav.tabs a[aria-current="page"] .num{color:var(--orange-ink)}
nav.tabs a .tick{color:var(--ok);font-weight:800;font-size:.8rem}
.pager{display:flex;justify-content:space-between;gap:.6rem;margin:1.6rem 0 0;padding-top:1rem;border-top:1px solid var(--line)}
.pager a{flex:1;max-width:48%;display:flex;flex-direction:column;text-decoration:none;color:var(--ink);background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:.6rem .9rem;min-height:56px;justify-content:center}
.pager a small{color:var(--muted);font-size:.78rem;font-weight:600;text-transform:uppercase;letter-spacing:.06em}
.pager a b{font-size:.98rem}
.pager a.next{text-align:right;margin-left:auto;border-color:var(--ink)}
.pager a:hover{border-color:var(--orange)}

main{max-width:1240px;margin:0 auto;padding:1.1rem 1rem 3rem}
main:focus{outline:none}
section.screen{display:none}
section.screen.on{display:block}
.crumb{font-size:.8rem;color:var(--muted);margin-bottom:.3rem;display:flex;gap:.3rem;flex-wrap:wrap;align-items:center}
.lede{max-width:72ch;color:var(--ink-2)}
.code{display:inline-block;font-weight:700;font-size:.75rem;color:var(--blue);background:var(--blue-soft);border:1px solid var(--blue-line);border-radius:6px;padding:0 .4rem;margin-right:.2rem;vertical-align:.1em}
.ext{display:inline-block;font-weight:700;font-size:.75rem;color:var(--orange-ink);background:var(--orange-soft);border:1px solid var(--orange-line);border-radius:6px;padding:0 .4rem;vertical-align:.1em}

.grid{display:grid;gap:1rem}
@media(min-width:900px){.grid.two{grid-template-columns:minmax(0,1.1fr) minmax(0,1fr)}.grid.even{grid-template-columns:1fr 1fr}.grid.three{grid-template-columns:repeat(3,1fr)}}
@media(min-width:640px) and (max-width:899px){.grid.three{grid-template-columns:1fr 1fr}}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:1rem 1.1rem;min-width:0}
.card.tight{padding:.75rem}
.card h3{color:var(--ink)}
.why{border-left:3px solid var(--orange);background:var(--g1);padding:.6rem .85rem;border-radius:0 8px 8px 0;margin:.6rem 0}
.why b:first-child{color:var(--orange-ink)}
.note{font-size:.88rem;color:var(--ink-2)}
.muted{color:var(--muted)} .small{font-size:.88rem}
.astar{border:1px solid var(--ink);border-radius:var(--radius);padding:.9rem 1.1rem;background:#fff}
.astar h3{color:var(--ink);text-transform:uppercase;font-size:.8rem;letter-spacing:.08em}
.astar h3::before{content:"A* · ";color:var(--orange-ink)}
ul.tight{margin:.3rem 0 .6rem;padding-left:1.2rem} ul.tight li{margin:.15rem 0}
figure.mic{margin:0}
figure.mic img{width:100%;height:auto;display:block;border-radius:8px;border:1px solid var(--line);background:#fff}
figure.mic figcaption{font-size:.8rem;color:var(--muted);margin-top:.35rem;line-height:1.4}
figure.mic figcaption b{color:var(--ink)}

/* ---------- buttons and controls ---------- */
button,.btn{font:inherit;font-size:.93rem;font-weight:600;min-height:44px;padding:.5rem .95rem;border-radius:10px;border:1px solid #C3C9CF;background:#fff;color:var(--ink);cursor:pointer;touch-action:manipulation;display:inline-flex;align-items:center;justify-content:center;gap:.35rem;text-decoration:none}
button:hover,.btn:hover{border-color:var(--ink)}
button.primary{background:var(--orange);border-color:var(--orange);color:#111}
button.primary:hover{background:#E06F0E}
button.dark{background:var(--ink);color:#fff;border-color:var(--ink)}
button.blue{background:var(--blue);color:#fff;border-color:var(--blue)}
button[aria-pressed="true"]{background:var(--ink);color:#fff;border-color:var(--ink)}
button:disabled{opacity:.55;cursor:not-allowed}
.opt:disabled{opacity:1;cursor:default}
.row{display:flex;flex-wrap:wrap;gap:.5rem;align-items:center}
.seg{display:inline-flex;border:1px solid #C3C9CF;border-radius:10px;overflow:hidden;background:#fff}
.seg button{border:0;border-radius:0;min-height:40px;padding:.4rem .85rem}
.seg button+button{border-left:1px solid #C3C9CF}
.ctl{display:grid;grid-template-columns:minmax(0,auto) minmax(120px,1fr) auto;gap:.6rem;align-items:center;margin:.35rem 0}
.ctl label{font-size:.88rem;font-weight:600}
.ctl output{font-variant-numeric:tabular-nums;font-size:.9rem;min-width:4.8em;text-align:right;font-weight:600}
@media(max-width:600px){.ctl{grid-template-columns:1fr auto;gap:0 .5rem}.ctl input[type=range]{grid-column:1/-1;order:3}}
input[type=range]{-webkit-appearance:none;appearance:none;width:100%;min-height:44px;background:transparent;margin:0;cursor:pointer}
input[type=range]::-webkit-slider-runnable-track{height:6px;border-radius:3px;background:var(--g3)}
input[type=range]::-moz-range-track{height:6px;border-radius:3px;background:var(--g3)}
input[type=range]::-webkit-slider-thumb{-webkit-appearance:none;width:24px;height:24px;border-radius:50%;background:var(--ink);border:3px solid #fff;box-shadow:0 0 0 1px var(--ink);margin-top:-9px}
input[type=range]::-moz-range-thumb{width:20px;height:20px;border-radius:50%;background:var(--ink);border:3px solid #fff;box-shadow:0 0 0 1px var(--ink)}
input[type=range]:focus-visible{outline:3px solid var(--blue-2);outline-offset:2px}
select{font:inherit;min-height:44px;border-radius:10px;border:1px solid #C3C9CF;padding:.3rem .6rem;background:#fff;width:100%}
.readouts{display:grid;grid-template-columns:repeat(auto-fit,minmax(118px,1fr));gap:.5rem;margin:.6rem 0}
.ro{background:var(--g1);border-radius:10px;padding:.45rem .65rem;border:1px solid var(--line)}
.ro small{display:block;color:var(--muted);font-size:.76rem;font-weight:600}
.ro b{font-size:1.05rem;font-variant-numeric:tabular-nums}
.pill{display:inline-block;border-radius:999px;padding:.05rem .6rem;font-size:.82rem;font-weight:700}
.pill.open{background:var(--ok-soft);color:var(--ok);border:1px solid var(--ok-line)}
.pill.shut{background:var(--g2);color:var(--ink-2);border:1px solid var(--g3)}
.phase{font-weight:750;font-size:1.05rem;color:var(--ink);min-height:1.6em}

/* ---------- 3D heart stage ---------- */
.stage{position:relative;border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;background:#EEF0F2}
.h3d{position:relative;height:min(56vh,520px);min-height:300px;background:radial-gradient(ellipse at 50% 38%,#FBFBFC 0%,#ECEEF1 62%,#E2E5E9 100%)}
.h3d-canvas{position:absolute;inset:0;width:100%;height:100%;display:block;touch-action:none;outline:none}
.h3d-canvas:focus-visible{box-shadow:inset 0 0 0 3px var(--blue-2)}
.h3d-label{position:absolute;max-width:calc(100% - 12px);z-index:3;background:var(--ink);color:#fff;font-size:.85rem;font-weight:600;padding:.3rem .6rem;border-radius:8px;transform:translate(14px,-50%);pointer-events:none;white-space:nowrap;box-shadow:0 2px 8px rgba(0,0,0,.18)}
.h3d-label::before{content:"";position:absolute;left:-14px;top:50%;width:12px;height:2px;background:var(--ink)}
.h3d-label.flip{transform:translate(calc(-100% - 14px),-50%)}
.h3d-label.flip::before{left:auto;right:-14px}
.h3d-load{position:absolute;inset:0;display:grid;place-items:center;color:var(--muted);font-size:.9rem}
.h3d.h3d-ready .h3d-load{display:none}
.h3d-hint{position:absolute;left:.6rem;bottom:.5rem;font-size:.75rem;color:var(--muted);pointer-events:none}
.stagebar{display:flex;flex-wrap:wrap;gap:.4rem;padding:.5rem;background:#fff;border-top:1px solid var(--line);align-items:center}
.stagebar .sp{flex:1}
.stage .svgwrap{background:#fff;padding:.4rem}
.transport{display:grid;grid-template-columns:auto auto auto 1fr auto;gap:.45rem;align-items:center;padding:.5rem .6rem;background:#fff;border-top:1px solid var(--line)}
.transport input[type=range]{min-width:0}
.transport output{font-variant-numeric:tabular-nums;font-weight:600;min-width:3.6em;text-align:right}
@media(max-width:600px){.h3d{height:44vh;min-height:270px}.transport{grid-template-columns:auto auto auto 1fr}.transport output{grid-column:4;text-align:right}.transport input[type=range]{grid-column:1/-1;order:5}}

/* ---------- SVG figures ---------- */
svg.fig{width:100%;height:auto;display:block;touch-action:pan-y;user-select:none;-webkit-user-select:none}
svg text{font-family:var(--font)}
.hot{cursor:pointer;touch-action:none}
.hot:focus{outline:none}
.hot:focus-visible circle.hs,.hot.sel circle.hs{stroke:var(--orange);stroke-width:4}
.hot:focus-visible circle.ring{stroke:var(--blue-2);stroke-width:5}
.chips{display:flex;flex-wrap:wrap;gap:.4rem}
.chip{font-size:.88rem;min-height:44px;padding:.35rem .75rem;border-radius:999px;border:1px solid #C3C9CF;background:#fff;cursor:pointer;font-weight:600}
.chip .n{display:inline-grid;place-items:center;width:1.4rem;height:1.4rem;border-radius:50%;background:var(--ink);color:#fff;font-size:.75rem;margin-right:.35rem}
.chip.sel{border-color:var(--orange);box-shadow:0 0 0 2px var(--orange)}
.infobox{min-height:7rem}
.infobox h3{margin-bottom:.3rem}

/* ---------- glossary ---------- */
button.term{all:unset;cursor:help;border-bottom:2px dotted var(--blue);color:inherit;font-weight:600}
button.term:focus-visible{outline:3px solid var(--blue-2);outline-offset:1px}
#gloss{position:fixed;left:50%;bottom:12px;transform:translateX(-50%);width:min(560px,calc(100% - 20px));background:var(--ink);color:#fff;border-radius:12px;padding:.9rem 3.2rem .9rem 1rem;z-index:50;box-shadow:0 10px 30px rgba(0,0,0,.3);display:none}
#gloss.on{display:block}
#gloss b{color:#F9A65A}
#gloss button{position:absolute;right:6px;top:6px;min-height:44px;min-width:44px;padding:0;background:transparent;color:#fff;border-color:#59606A}

/* ---------- drag and drop ---------- */
.dnd-pool{display:flex;flex-wrap:wrap;gap:.5rem;min-height:56px;padding:.5rem;border:1px dashed var(--g4);border-radius:12px;background:var(--g1)}
.dcard{background:#fff;border:1px solid var(--ink);border-radius:10px;padding:.45rem .65rem .45rem .45rem;font-size:.9rem;cursor:grab;touch-action:pan-y;user-select:none;-webkit-user-select:none;min-height:44px;max-width:100%;text-align:left;line-height:1.3;display:inline-flex;gap:.4rem;align-items:center;font-weight:500}
.dcard .grip{touch-action:none;display:inline-grid;place-items:center;min-width:28px;min-height:36px;color:var(--g4);font-size:1.1rem;border-right:1px solid var(--g2);margin-right:.1rem;cursor:grab}
.dcard.sel{border-color:var(--orange);box-shadow:0 0 0 3px var(--orange)}
.dcard.ok{border-color:var(--ok);background:var(--ok-soft);cursor:default}
.dcard.bad{border-color:var(--bad);background:var(--bad-soft)}
.dcard.img{padding:.3rem;flex-direction:column;align-items:stretch;gap:.25rem;width:150px}
.dcard.img .grip{border-right:0;border-bottom:1px solid var(--g2);min-height:24px}
.dcard.img img{width:100%;height:110px;object-fit:cover;border-radius:6px;display:block}
.dcard.img svg{width:116px;height:116px}
.dcard.img small{font-size:.75rem;color:var(--muted)}
.dragging{position:fixed;z-index:60;pointer-events:none;opacity:.94;box-shadow:0 8px 20px rgba(0,0,0,.22)}
.zones{display:grid;gap:.6rem;margin-top:.6rem}
@media(min-width:700px){.zones.c3{grid-template-columns:repeat(3,1fr)}.zones.c4{grid-template-columns:repeat(4,1fr)}.zones.c6{grid-template-columns:repeat(3,1fr)}}
@media(min-width:420px) and (max-width:699px){.zones.c4,.zones.c6{grid-template-columns:1fr 1fr}}
.zone{border:1px dashed var(--g4);border-radius:12px;padding:.5rem;min-height:88px;background:#fff;display:flex;flex-direction:column;gap:.4rem}
.zone > .zt{font-weight:700;font-size:.88rem;color:var(--blue)}
.zone.hover,.zone.armed{border-color:var(--orange);border-style:solid;background:var(--orange-soft)}
.fb{margin-top:.6rem;padding:.6rem .85rem;border-radius:10px;display:none}
.fb.on{display:block}
.fb.good{background:var(--ok-soft);border:1px solid var(--ok-line)}
.fb.poor{background:var(--bad-soft);border:1px solid var(--bad-line)}
.fb.ok{background:var(--orange-soft);border:1px solid var(--orange-line)}
.fb.info{background:var(--blue-soft);border:1px solid var(--blue-line)}

/* ---------- drawing task ---------- */
.drawtools{margin-bottom:.4rem}
.drawtools .lblin{flex:1 1 160px;min-height:44px;border:1px solid #C3C9CF;border-radius:10px;padding:.3rem .6rem;font:inherit}
canvas.drawpad{width:100%;display:block;border:1px solid var(--g4);border-radius:10px;background:#fff;touch-action:none;cursor:crosshair}
.drawcmp{margin-top:.8rem;padding-top:.8rem;border-top:1px solid var(--line)}
ul.checks{list-style:none;padding:0;margin:.3rem 0}
ul.checks li{padding:.2rem 0}
ul.checks label{display:flex;gap:.5rem;align-items:flex-start;min-height:32px}
ul.checks input{width:22px;height:22px;flex:none}

/* ---------- quiz ---------- */
.q{border-top:1px solid var(--line);padding:1rem 0}
.q:first-child{border-top:0}
.q .stem{font-weight:600}
.opts{display:grid;gap:.45rem;margin:.5rem 0}
.opt{text-align:left;display:flex;gap:.6rem;align-items:flex-start;justify-content:flex-start;line-height:1.35;font-weight:500}
.opt .L{flex:none;font-weight:800;width:1.6rem;height:1.6rem;border-radius:50%;display:grid;place-items:center;background:var(--g1);border:1px solid var(--line)}
.opt.right{border-color:var(--ok);background:var(--ok-soft)}
.opt.wrong{border-color:var(--bad);background:var(--bad-soft)}
.opt .mk{margin-left:auto;font-size:.8rem;font-weight:800;white-space:nowrap;padding-left:.5rem}
.opt.right .mk{color:var(--ok)} .opt.wrong .mk{color:var(--bad)}
textarea{width:100%;min-height:120px;font:inherit;font-size:.95rem;padding:.6rem;border-radius:10px;border:1px solid var(--g4)}
.ms{list-style:none;padding:0;margin:.5rem 0}
.ms li{display:flex;gap:.5rem;align-items:flex-start;padding:.3rem 0}
.ms input{width:22px;height:22px;flex:none;margin-top:.15rem}
.ms .hint{font-size:.78rem;color:var(--ok);font-weight:700;margin-left:.3rem}
.ms .ari{display:block;font-size:.8rem;color:var(--ink-2);margin-top:.1rem}
.ms .part{font-size:.78rem;font-weight:800;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);padding-top:.5rem}
.score{font-weight:800;font-size:1.05rem}

/* ---------- home ---------- */
.hero{background:var(--ink);color:#fff;border-radius:16px;padding:1.4rem 1.4rem 1.1rem}
.hero h1{color:#fff;font-size:1.75rem}
.hero p{color:#E3E6EA;max-width:75ch}
.hero .k{color:#F9A65A}
.hero button.term{border-bottom-color:#F9A65A}
.hero .row{margin-top:.6rem}
.tiles{display:grid;gap:.7rem;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));margin-top:.8rem}
.tile{display:block;text-decoration:none;color:var(--ink);background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:.8rem .95rem;min-height:44px}
.tile .tn{font-size:.75rem;font-weight:800;color:var(--orange-ink);letter-spacing:.06em}
.tile b{display:block;color:var(--ink)}
.tile small{color:var(--ink-2)}
.tile:hover{border-color:var(--ink)}
table.simple{border-collapse:collapse;width:100%;font-size:.9rem}
table.simple th,table.simple td{border:1px solid var(--line);padding:.4rem .55rem;text-align:left;vertical-align:top}
table.simple th{background:var(--g2);color:var(--ink)}
.tablewrap{overflow-x:auto}
footer.ft{max-width:1240px;margin:0 auto;padding:1rem;color:var(--muted);font-size:.83rem;border-top:1px solid var(--line);display:flex;flex-wrap:wrap;gap:.5rem;justify-content:space-between;align-items:center}
footer.ft a{color:var(--ink-2)}
#errbar{display:none;position:fixed;top:0;left:0;right:0;background:var(--bad);color:#fff;padding:.5rem 1rem;z-index:99;font-size:.9rem}
.steps{display:flex;gap:.3rem;flex-wrap:wrap;margin:.4rem 0}
.steps button{min-width:44px;padding:.3rem .5rem}
.kbd{font-family:ui-monospace,Consolas,monospace;font-size:.85rem;background:var(--g2);border-radius:5px;padding:0 .3rem}
.credits td{font-size:.85rem}
.credits img{width:72px;height:54px;object-fit:cover;border-radius:4px;border:1px solid var(--line)}
@media(max-width:600px){h1{font-size:1.35rem}.hero h1{font-size:1.4rem}.card{padding:.8rem}main{padding:.8rem .65rem 3rem}.brandtxt small{display:none}.brandbar{padding:.35rem .75rem .1rem}}
@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}}
@media print{header.top,nav.tabs,footer.ft,.pager{display:none}section.screen{display:block!important;page-break-after:always}}

/* ---------- iOS-style app shell (phones and Home Screen) ---------- */
.tabbar{display:none}
.subnav{display:none}
@media(max-width:700px){
  header.top{padding-top:env(safe-area-inset-top)}
  header.top nav.tabs{display:none}
  .brandbar{padding-left:max(.75rem,env(safe-area-inset-left));padding-right:max(.75rem,env(safe-area-inset-right))}
  main{padding-bottom:calc(84px + env(safe-area-inset-bottom));padding-left:max(.65rem,env(safe-area-inset-left));padding-right:max(.65rem,env(safe-area-inset-right))}
  footer.ft{padding-bottom:calc(90px + env(safe-area-inset-bottom))}
  .tabbar{display:grid;grid-template-columns:repeat(5,1fr);position:fixed;left:0;right:0;bottom:0;z-index:30;background:rgba(255,255,255,.94);-webkit-backdrop-filter:saturate(180%) blur(18px);backdrop-filter:saturate(180%) blur(18px);border-top:1px solid var(--line);padding:4px max(6px,env(safe-area-inset-left)) calc(4px + env(safe-area-inset-bottom)) max(6px,env(safe-area-inset-right))}
  .tabbar a{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:2px;min-height:50px;text-decoration:none;color:#7A828B;font-size:.68rem;font-weight:600;letter-spacing:.01em;-webkit-tap-highlight-color:transparent}
  .tabbar svg{width:26px;height:26px;fill:none;stroke:currentColor;stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round}
  .tabbar a[aria-current="true"]{color:var(--orange-ink)}
  .tabbar a[aria-current="true"] svg{stroke-width:2.1}
  .subnav{display:flex;gap:0;margin:-.2rem 0 .8rem;background:var(--g2);border-radius:10px;padding:3px;overflow-x:auto;scrollbar-width:none}
  .subnav::-webkit-scrollbar{display:none}
  .subnav a{flex:1 0 auto;text-align:center;text-decoration:none;color:var(--ink-2);font-size:.82rem;font-weight:650;padding:.5rem .7rem;border-radius:8px;min-height:36px;white-space:nowrap}
  .subnav a[aria-current="page"]{background:#fff;color:var(--ink);box-shadow:0 1px 3px rgba(0,0,0,.12)}
  #gloss{bottom:calc(76px + env(safe-area-inset-bottom))}
  .pager{margin-top:1.2rem}
}
@media(display-mode:standalone){body{-webkit-user-select:none;user-select:none;-webkit-touch-callout:none}input,textarea,.lede,p,li,td,figcaption{-webkit-user-select:text;user-select:text}html,body{overscroll-behavior-y:none}}
body{-webkit-tap-highlight-color:transparent}
section.screen.on{animation:screenIn .28s cubic-bezier(.2,.8,.2,1)}
section.screen.on.back{animation-name:screenBack}
@keyframes screenIn{from{opacity:0;transform:translateX(18px)}to{opacity:1;transform:none}}
@keyframes screenBack{from{opacity:0;transform:translateX(-18px)}to{opacity:1;transform:none}}
.ms li.part{font-weight:800;font-size:.85rem;color:var(--blue);padding-top:.6rem;text-transform:none}

/* Heart stage on phones: the four view buttons share one row, the 3D/2D switch sits over the canvas corner,
   and the canvas height is set so header + stage + transport fit on one iPhone screen above the tab bar. */
.sm{display:none}
@media(max-width:600px){
  .lg{display:none}.sm{display:inline}
  .stagebar{position:relative;flex-wrap:nowrap;min-height:44px}
  .stagebar .sp{display:none}
  .stagebar>button{flex:1 1 0;padding:.4rem .3rem;min-width:0;white-space:nowrap}
  .stagebar .seg{position:absolute;top:calc(100% + .5rem);right:.5rem;z-index:3;box-shadow:0 1px 3px rgba(20,23,26,.12)}
  .stagebar .seg button{min-width:44px;min-height:40px;padding:.3rem .6rem}
  .h3d{height:clamp(260px,calc(100svh - 548px),440px);min-height:0}
  .transport{padding:.4rem .5rem;row-gap:.25rem}
}