/* THE TRADE-OFF ROOM — brutalist showroom: concrete, steel, translucent plates, one signal colour. */
:root{
  --concrete:#ECEAE4;--concrete-2:#E1DED6;--ink:#121212;--muted:#4E4B45;--steel:#2A2A2A;
  --signal:#C2380F;--signal-soft:rgba(194,56,15,.12);--glass:rgba(255,255,255,.55);--line:#121212;
  --mono:ui-monospace,SFMono-Regular,Menlo,Consolas,"Liberation Mono",monospace;
  --sans:"Helvetica Neue",Helvetica,Arial,system-ui,sans-serif;
  --max:1280px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:84px}
body{margin:0;background:var(--concrete);color:var(--ink);font:17px/1.6 var(--sans);-webkit-font-smoothing:antialiased;overflow-x:hidden;
  background-image:linear-gradient(rgba(18,18,18,.045) 1px,transparent 1px),linear-gradient(90deg,rgba(18,18,18,.045) 1px,transparent 1px);background-size:48px 48px}
a{color:inherit;text-underline-offset:3px;text-decoration-thickness:1px}
a:hover{color:var(--signal)}
:focus-visible{outline:3px solid var(--signal);outline-offset:3px}
button{font:inherit;cursor:pointer;color:inherit}
q{quotes:"“" "”"}
.wrap{width:min(var(--max),calc(100% - 64px));margin-inline:auto}
.skip{position:absolute;left:12px;top:-60px;background:var(--ink);color:var(--concrete);padding:10px 14px;z-index:100}
.skip:focus{top:12px}

/* header */
.top{position:sticky;top:0;z-index:50;background:rgba(236,234,228,.9);backdrop-filter:blur(8px);border-bottom:2px solid var(--line)}
.top-in{display:flex;align-items:center;justify-content:space-between;gap:24px;min-height:66px}
.mark{display:flex;align-items:center;gap:10px;text-decoration:none;font:800 14px/1 var(--mono);letter-spacing:.08em}
.top nav{display:flex;gap:22px;align-items:center;flex-wrap:wrap}
.top nav a{font:12px var(--mono);letter-spacing:.1em;text-transform:uppercase;text-decoration:none;padding:10px 0}
.top nav .nav-home{background:var(--ink);color:var(--concrete);padding:10px 14px;white-space:nowrap}
.top nav .nav-home:hover{background:var(--signal);color:#fff}

/* type */
.eyebrow,.idx,.room-n,.ro-k,.rd-k,.pick-count,.ledger-top span,.pan-label{font-family:var(--mono);letter-spacing:.14em;text-transform:uppercase}
.eyebrow,.idx{font-size:12px;color:var(--muted);margin:0 0 16px}
h1,h2,h3{letter-spacing:-.035em;line-height:1.02;margin:0}
h2{font-size:clamp(34px,5vw,68px);font-weight:900}
h2 span{display:block;color:var(--muted);font-weight:700}
.tag{display:inline-block;font:700 10px/1 var(--mono);letter-spacing:.1em;padding:4px 6px 3px;border:1.5px solid currentColor;vertical-align:2px;margin-right:4px}
.tag-fact{color:var(--ink);background:#fff}
.tag-int{color:#1F4F78;background:#E6EEF5}
.tag-inv{color:var(--signal);background:#FBEAE3}

/* buttons */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:10px;min-height:48px;padding:12px 20px;font:700 15px/1.2 var(--sans);text-decoration:none;border:2px solid var(--ink);transition:transform .15s,background .15s,color .15s,box-shadow .15s;text-align:center}
.btn:hover{transform:translate(-3px,-3px);box-shadow:4px 4px 0 var(--ink)}
.btn:active{transform:none;box-shadow:none}
.btn-solid{background:var(--signal);border-color:var(--signal);color:#fff}
.btn-solid:hover{color:#fff;background:#A32E0B}
.btn-line{background:var(--glass)}
.btn-sm{min-height:44px;padding:9px 14px;font-size:14px}
.btn-xl{min-height:60px;padding:16px 28px;font-size:18px}
.actions{display:flex;flex-wrap:wrap;gap:14px;margin:28px 0 10px}
.link-btn{background:none;border:0;padding:10px 0;min-height:44px;text-decoration:underline;font-size:13px;color:var(--muted)}

/* hero */
.hero{border-bottom:2px solid var(--line);padding:64px 0 36px;overflow:hidden}
.hero-grid{display:grid;grid-template-columns:1.25fr .75fr;gap:48px;align-items:center}
.kinetic{font-size:clamp(52px,8.6vw,132px);font-weight:900;line-height:.9;letter-spacing:-.06em;margin:0 0 26px}
.k{display:block}
.js .k{opacity:0;transform:translateY(.4em);animation:rise .8s cubic-bezier(.2,.8,.2,1) forwards}
.js .k2{animation-delay:.15s}.js .k3{animation-delay:.3s;color:var(--muted)}
@keyframes rise{to{opacity:1;transform:none}}
.tip{display:inline-block;color:var(--signal);transform-origin:50% 100%}
.js .tip{animation:tip 1.4s 1s cubic-bezier(.3,1.6,.5,1) both}
@keyframes tip{0%{transform:rotate(0)}40%{transform:rotate(-12deg)}100%{transform:rotate(-7deg)}}
.lead{font-size:clamp(18px,1.6vw,21px);max-width:620px;color:#2b2925}
.pdf-note{font:12px var(--mono);letter-spacing:.06em;color:var(--muted)}
.hero-plate{position:relative;height:420px}
.plate{position:absolute;width:72%;height:58%;border:2px solid var(--ink);background:var(--glass);backdrop-filter:blur(4px);display:flex;align-items:flex-start;padding:12px 14px;font:700 12px var(--mono);letter-spacing:.12em}
.plate-a{top:0;left:0}
.plate-b{top:22%;left:14%;background:rgba(194,56,15,.14);border-style:dashed}
.plate-c{top:44%;left:28%;background:rgba(18,18,18,.08)}
.js .plate{animation:drift 9s ease-in-out infinite alternate}
.js .plate-b{animation-delay:-3s}.js .plate-c{animation-delay:-6s}
@keyframes drift{to{transform:translate(10px,-8px)}}
.key{margin-top:40px;font-size:13px;color:var(--muted);display:flex;flex-wrap:wrap;gap:8px 18px;align-items:center}

/* sections */
.sec{padding:96px 0;border-bottom:2px solid var(--line)}
.sec-head{display:grid;gap:8px;margin-bottom:48px;max-width:920px}
.sec-desc{font-size:17px;color:#2b2925;max-width:760px;margin:14px 0 0}
.cols{display:grid;grid-template-columns:1.1fr .9fr;gap:56px;align-items:start}
.prose p{margin:0 0 18px;max-width:640px}
.prose q{font-style:italic}

/* seen / unseen */
.seen{margin:0;border:2px solid var(--ink);background:var(--glass);padding:22px;position:sticky;top:96px}
.seen figcaption{font-weight:700;margin-bottom:16px}
.seen-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin-bottom:18px}
.seen-col{border-top:2px solid var(--ink);padding-top:10px}
.seen-col ul{margin:0;padding-left:18px;font-size:15px}
.seen-col li{margin-bottom:8px}
.seen-h{font:700 11px var(--mono);letter-spacing:.14em;margin:0 0 8px}
.unseen{border-top-style:dashed;color:var(--signal)}
.js .unseen ul{filter:blur(6px);opacity:.35;transition:filter .6s,opacity .6s}
.js .unseen.is-on ul{filter:none;opacity:1}

/* rooms */
.rooms{background:var(--concrete-2)}
.fallback{border:2px dashed var(--ink);padding:18px;background:var(--glass)}
.tabs{display:grid;grid-template-columns:repeat(8,1fr);border:2px solid var(--ink);margin-bottom:-2px}
.room-tab{position:relative;display:flex;flex-direction:column;gap:6px;text-align:left;background:var(--concrete);border:0;border-right:2px solid var(--ink);padding:14px 12px 16px;min-height:96px;transition:background .15s}
.room-tab:last-child{border-right:0}
.room-tab:hover{background:#fff}
.room-tab[aria-pressed="true"]{background:var(--ink);color:var(--concrete)}
.rt-n{font:700 11px var(--mono);letter-spacing:.12em;opacity:.7}
.rt-t{font-weight:800;font-size:14px;line-height:1.2;letter-spacing:-.01em}
.rt-d{position:absolute;top:12px;right:12px;width:10px;height:10px;border:2px solid currentColor;border-radius:50%}
.room-tab.is-done .rt-d{background:var(--signal);border-color:var(--signal)}
.stage{border:2px solid var(--ink);background:rgba(255,255,255,.4);padding:32px}
.stage-top h3{font-size:clamp(30px,3.6vw,50px);font-weight:900;margin:6px 0 10px}
.stage-top h3:focus{outline:none}
.room-n{font-size:12px;color:var(--signal);margin:0}
.room-setup{max-width:720px;margin:0 0 20px;font-size:18px}
.stage-grid{display:grid;grid-template-columns:1.2fr .8fr;gap:32px;align-items:start}

/* svg scale */
.scale-wrap{border:2px solid var(--ink);background:var(--concrete);padding:10px 10px 0}
#scale{display:block;width:100%;height:auto;overflow:visible}
.steel{fill:var(--steel)}
.beam{fill:var(--ink)}
.joint{fill:var(--concrete);stroke:var(--ink);stroke-width:3}
.pivot{fill:var(--signal);stroke:var(--ink);stroke-width:3}
.string{stroke:var(--ink);stroke-width:1.5;fill:none}
.tray{fill:none;stroke:var(--ink);stroke-width:5;stroke-linecap:square}
.tray-given{stroke:var(--signal)}
.pan-label{font-size:12px;font-weight:700;fill:var(--ink)}
.pan-label-given{fill:var(--signal)}
.blk{fill:var(--ink);stroke:var(--ink);stroke-width:2}
.blk-ghost{fill:url(#hatch);stroke:var(--signal);stroke-dasharray:5 4}
.hatch-line{stroke:var(--signal);stroke-width:2;opacity:.45}
.blk-t{fill:var(--concrete);font:700 15px var(--mono)}
.blk-t-ghost{fill:var(--signal)}
.scale-caption{font-size:14px;color:var(--muted);margin:8px 6px 12px;min-height:3em}

/* options */
.pick-count{font-size:12px;margin:0 0 12px;color:var(--muted)}
.options{display:grid;gap:10px}
.opt{display:flex;align-items:center;gap:14px;text-align:left;min-height:64px;padding:12px 16px;background:var(--concrete);border:2px solid var(--ink);font-weight:700;font-size:16px;line-height:1.3;transition:transform .15s,background .15s,color .15s,opacity .25s}
.opt:hover{transform:translateX(4px)}
.opt-k{flex:none;display:grid;place-items:center;width:32px;height:32px;border:2px solid currentColor;font:700 13px var(--mono)}
.opt[aria-pressed="true"]{background:var(--ink);color:var(--concrete)}
.opt[aria-pressed="true"] .opt-k{background:var(--signal);border-color:var(--signal);color:#fff}
.opt.is-given{border-style:dashed;border-color:var(--signal);color:var(--signal);background:var(--signal-soft)}
.opt.is-given .opt-l{text-decoration:line-through;text-decoration-thickness:2px}

/* ledger */
.ledger{margin-top:22px;border-top:2px solid var(--ink);padding-top:14px}
.ledger-top{display:flex;justify-content:space-between;align-items:baseline}
.ledger-top span{font-size:11px;color:var(--muted)}
.ledger-top b{font:800 22px var(--mono)}
.ledger-bar{height:10px;border:2px solid var(--ink);margin:8px 0 10px;background:var(--concrete)}
.ledger-bar i{display:block;height:100%;background:var(--signal);transform-origin:0 50%;transform:scaleX(var(--p,0));transition:transform .6s cubic-bezier(.2,.8,.2,1)}
.ledger-mirror{font-size:14px;margin:0 0 6px;color:#2b2925}
.ledger-done{font-size:14px;background:var(--ink);color:var(--concrete);padding:12px 14px;margin:10px 0}
.room-lit .rooms{background:#F3E2DA;transition:background 1s}

/* readout */
.readout{margin-top:28px;border-top:2px solid var(--ink);padding-top:24px}
.ro-head{display:flex;flex-wrap:wrap;align-items:baseline;gap:6px 18px;margin-bottom:18px}
.ro-k{font-size:12px;color:var(--signal);margin:0}
.ro-given{font-size:clamp(22px,2.4vw,30px);font-weight:900;letter-spacing:-.02em;margin:0;text-decoration:line-through;text-decoration-color:var(--signal);text-decoration-thickness:3px}
.ro-weight{margin:0;font:13px var(--mono)}
.ro-weight b[data-w="3"]{color:var(--signal)}
.lenses{display:grid;grid-template-columns:repeat(4,1fr);border:2px solid var(--ink)}
.lens{padding:18px;border-right:2px solid var(--ink);background:var(--glass)}
.lens:last-child{border-right:0}
.lens h4{margin:0 0 10px;font-size:15px;letter-spacing:-.01em}
.lens h4 span{font:700 11px var(--mono);color:var(--muted);margin-right:6px}
.lens p{margin:0;font-size:15px;line-height:1.55}
.lens-hot{background:var(--signal-soft)}
.ro-foot{display:flex;align-items:center;flex-wrap:wrap;gap:12px;margin-top:16px}
.share-msg{font-size:13px;color:var(--muted)}

/* principles */
.principles{display:grid;grid-template-columns:repeat(3,1fr);border:2px solid var(--ink)}
.pr{padding:26px;border-right:2px solid var(--ink);border-bottom:2px solid var(--ink);background:var(--glass)}
.pr:nth-child(3n){border-right:0}
.pr:nth-last-child(-n+3){border-bottom:0}
.pr svg{width:120px;height:80px;display:block;margin-bottom:14px}
.pr h3{font-size:22px;font-weight:900;margin-bottom:10px}
.pr h3 span{font:700 12px var(--mono);color:var(--signal);vertical-align:4px;margin-right:4px}
.pr p{font-size:15px;margin:0}
.fill-ink{fill:var(--ink)}.fill-sig{fill:var(--signal)}
.dash{fill:none;stroke:var(--ink);stroke-width:2.5;stroke-dasharray:6 4}
.ln{fill:none;stroke:var(--ink);stroke-width:3}
.ln-sig{stroke:var(--signal)}
.svg-t{font:800 16px var(--mono);fill:var(--ink)}
.svg-t-inv{font:800 16px var(--mono);fill:var(--concrete)}
.pr:hover .fill-sig{transform:scale(1.08);transform-box:fill-box;transform-origin:center;transition:transform .3s}

/* redesign */
.rd-grid{display:grid;grid-template-columns:1fr 1fr;gap:20px}
.redesign{border:2px solid var(--ink);padding:24px;background:var(--glass);display:flex;flex-direction:column;gap:14px}
.rd-k{font-size:11px;color:var(--signal);margin:0}
.rd-body{display:grid;position:relative}
.rd-before,.rd-after{grid-area:1/1;transition:opacity .4s,transform .4s}
.rd-body h3{font-size:13px;font-family:var(--mono);letter-spacing:.12em;text-transform:uppercase;margin-bottom:8px;color:var(--muted)}
.rd-before p{font-size:clamp(22px,2.2vw,28px);font-weight:900;letter-spacing:-.02em;line-height:1.15;margin:0}
.rd-after p{margin:0}
.rd-after{opacity:0;transform:translateY(10px);pointer-events:none}
.is-redesigned .rd-before{opacity:0;transform:translateY(-10px)}
.is-redesigned .rd-after{opacity:1;transform:none;pointer-events:auto}
.rd-toggle{align-self:flex-start;margin-top:auto}

/* sources */
.sources{padding-left:22px;max-width:920px}
.sources li{margin-bottom:10px;font-size:15px}
.disclaimer{font-size:14px;color:var(--muted);border-left:4px solid var(--ink);padding-left:14px;max-width:760px;margin-top:28px}

/* takeaways */
.tk-list{counter-reset:tk;list-style:none;padding:0;display:grid;grid-template-columns:repeat(4,1fr);border:2px solid var(--ink);margin:0 0 40px}
.tk-list li{counter-increment:tk;padding:22px;border-right:2px solid var(--ink);font-size:15px}
.tk-list li:last-child{border-right:0}
.tk-list li::before{content:"0" counter(tk);display:block;font:800 28px var(--mono);color:var(--signal);margin-bottom:8px}
.tk-list b{display:block;font-size:18px;line-height:1.25;margin-bottom:6px}
.pdf-card{display:grid;grid-template-columns:180px 1fr;gap:32px;align-items:center;border:2px solid var(--ink);background:#fff;padding:28px;box-shadow:10px 10px 0 var(--ink)}
.pdf-card h3{font-size:30px;font-weight:900;margin-bottom:10px}
.pdf-card p{margin:0 0 18px;max-width:680px}
.pdf-thumb{aspect-ratio:1/1.414;background:var(--ink);color:var(--concrete);padding:14px;display:flex;align-items:flex-end;font:900 18px/1 var(--sans);letter-spacing:-.03em;border-bottom:10px solid var(--signal);transform:rotate(-3deg)}

/* contact */
.contact{background:var(--ink);color:var(--concrete);padding:100px 0}
.contact h2 span{color:#F28B66}
.contact p{max-width:620px;font-size:18px;color:#cfccc4}
.contact .btn-line{background:transparent;color:var(--concrete);border-color:var(--concrete)}
.contact .btn-line:hover{box-shadow:4px 4px 0 var(--concrete)}
.contact .btn-solid:hover{box-shadow:4px 4px 0 var(--concrete)}
.contact :focus-visible{outline-color:#F28B66}

/* footer */
.foot{padding:40px 0;font-size:14px}
.foot-in{display:grid;grid-template-columns:1fr auto;gap:18px 32px;align-items:start}
.foot nav{display:flex;flex-wrap:wrap;gap:6px 20px}
.foot nav a{padding:10px 0;display:inline-block}
.foot-small{grid-column:1/-1;color:var(--muted);font-size:13px;margin:0}

/* reveal */
.js .rv{opacity:0;transform:translateY(24px);transition:opacity .7s cubic-bezier(.2,.8,.2,1),transform .7s cubic-bezier(.2,.8,.2,1)}
.js .rv.in{opacity:1;transform:none}

/* responsive */
@media (max-width:1100px){
  .tabs{grid-template-columns:repeat(4,1fr)}
  .room-tab:nth-child(4){border-right:0}
  .room-tab:nth-child(-n+4){border-bottom:2px solid var(--ink)}
  .stage-grid{grid-template-columns:1fr}
  .lenses{grid-template-columns:1fr 1fr}
  .lens:nth-child(2){border-right:0}
  .lens:nth-child(-n+2){border-bottom:2px solid var(--ink)}
  .principles{grid-template-columns:1fr 1fr}
  .pr:nth-child(3n){border-right:2px solid var(--ink)}
  .pr:nth-child(2n){border-right:0}
  .pr:nth-last-child(-n+3){border-bottom:2px solid var(--ink)}
  .pr:nth-last-child(-n+2){border-bottom:0}
  .tk-list{grid-template-columns:1fr 1fr}
  .tk-list li:nth-child(2){border-right:0}
  .tk-list li:nth-child(-n+2){border-bottom:2px solid var(--ink)}
}
@media (max-width:820px){
  .top nav a:not(.nav-home){display:none}
  .hero-grid,.cols{grid-template-columns:1fr}
  .hero-plate{height:220px}
  .seen{position:static}
  .rd-grid{grid-template-columns:1fr}
  .pdf-card{grid-template-columns:1fr;box-shadow:6px 6px 0 var(--ink)}
  .pdf-thumb{width:120px}
}
@media (max-width:560px){
  body{font-size:16px}
  .wrap{width:calc(100% - 32px)}
  .sec{padding:64px 0}
  .tabs{grid-template-columns:1fr 1fr}
  .room-tab{border-right:2px solid var(--ink)!important;border-bottom:2px solid var(--ink)}
  .room-tab:nth-child(2n){border-right:0!important}
  .room-tab:nth-last-child(-n+2){border-bottom:0}
  .stage{padding:18px}
  .lenses,.principles,.tk-list{grid-template-columns:1fr}
  .lens,.pr,.tk-list li{border-right:0!important;border-bottom:2px solid var(--ink)!important}
  .lens:last-child,.pr:last-child,.tk-list li:last-child{border-bottom:0!important}
  .seen-grid{grid-template-columns:1fr}
  .btn{width:100%}
  .actions{flex-direction:column}
  .foot-in{grid-template-columns:1fr}
  .mark span{font-size:11px}
  .mark svg{width:24px;height:24px}
  .top nav .nav-home{padding:10px 10px;font-size:11px}
  .pan-label{font-size:16px}
  .blk-t{font-size:17px}
}
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  .js .k,.js .tip,.js .plate,.js .rv{animation:none!important;opacity:1!important;transform:none!important;transition:none!important}
  .js .tip{transform:rotate(-7deg)!important}
  .btn,.opt,.rd-before,.rd-after,.ledger-bar i,.js .unseen ul{transition:none}
  .btn:hover{transform:none}
}