/* Urban Science AI Lab — site stylesheet
   Order: tokens → base → header/nav → buttons → hero → page hero → sections → cards → agenda → footer → responsive */
:root{
  --navy:#0b1830;--navy-2:#15244a;--blue:#2459e0;--blue-2:#1f4fcf;--sky:#dfeaff;--sky-2:#eef4ff;
  --white:#fbfcff;--surface:#ffffff;--muted:#5f6a80;--line:#dbe1ec;--line-2:#c3cde0;
  --radius:18px;--radius-s:12px;--max:1160px;--pad:24px;
  --sans:Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",sans-serif;
  --mono:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;color:var(--navy);background:var(--white);font:16px/1.65 var(--sans);-webkit-font-smoothing:antialiased}
a{color:inherit}
h1,h2,h3{text-wrap:balance;margin:0}
p{margin:0}
:focus-visible{outline:2px solid var(--blue);outline-offset:3px;border-radius:4px}
.skip{position:absolute;left:-999px;top:8px;z-index:50;background:var(--navy);color:#fff;padding:8px 12px;border-radius:8px;font-weight:800;text-decoration:none}
.skip:focus{left:12px}

/* header / nav */
header{position:sticky;top:0;z-index:20;background:rgba(251,252,255,.9);backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}
.nav{position:relative;max-width:var(--max);margin:auto;padding:14px var(--pad);display:flex;justify-content:space-between;align-items:center;gap:20px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;font-weight:850;letter-spacing:-.02em;white-space:nowrap}
.brand-mark{width:26px;height:26px;border-radius:50%;border:2px solid var(--navy);position:relative;flex:0 0 auto}
.brand-mark:before{content:"";position:absolute;inset:5px;border-radius:50%;background:var(--blue)}
.nav nav{display:flex;gap:22px;align-items:center}
.nav nav a{position:relative;text-decoration:none;color:var(--muted);font-size:14px;white-space:nowrap}
.nav nav a:hover,.nav nav a[aria-current="page"]{color:var(--navy)}
.nav nav a[aria-current="page"]:after{content:"";position:absolute;left:0;right:0;bottom:-8px;height:2px;background:var(--blue);border-radius:2px}
.nav nav a.cta{background:var(--navy);color:#fff;padding:8px 14px;border-radius:999px;font-weight:750}
.nav nav a.cta:hover{background:var(--blue)}
.nav-toggle{display:none;background:none;border:1px solid var(--line-2);color:var(--navy);border-radius:10px;width:40px;height:36px;cursor:pointer;padding:0}
.nav-toggle span{display:block;width:18px;height:2px;background:currentColor;margin:3px auto;transition:.2s}
.nav-toggle[aria-expanded="true"] span:nth-child(1){transform:translateY(5px) rotate(45deg)}
.nav-toggle[aria-expanded="true"] span:nth-child(2){opacity:0}
.nav-toggle[aria-expanded="true"] span:nth-child(3){transform:translateY(-5px) rotate(-45deg)}

main{max-width:var(--max);margin:auto;padding:0 var(--pad)}
.label{font-size:12px;letter-spacing:.15em;text-transform:uppercase;color:var(--blue);font-weight:850;margin-bottom:12px}
.lead{font-size:clamp(18px,2.2vw,24px);color:var(--muted);max-width:760px}
.intro{color:var(--muted);max-width:760px;margin:0 0 34px;font-size:18px}
.byline{margin-top:16px;font-size:14px;color:var(--muted)}
.byline a{color:var(--navy);font-weight:700;text-decoration:none;border-bottom:1px solid var(--line-2)}
.byline a:hover{border-color:var(--blue);color:var(--blue)}

/* buttons */
.button{display:inline-flex;align-items:center;gap:8px;background:var(--navy);color:#fff;padding:12px 19px;border-radius:999px;text-decoration:none;font-weight:750;font-size:14px;border:1px solid var(--navy);transition:.18s ease}
.button:hover{background:var(--blue);border-color:var(--blue)}
.button.ghost{background:transparent;color:var(--navy)}
.button.ghost:hover{background:var(--sky-2);color:var(--navy)}
.button.light{background:#fff;color:var(--navy);border-color:#fff}
.button.light:hover{background:var(--sky)}
.actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:28px}

/* hero */
.hero{padding:92px 0 72px;display:grid;grid-template-columns:1.15fr .85fr;gap:70px;align-items:center}
.hero h1{font-size:clamp(50px,7.6vw,92px);line-height:.95;letter-spacing:-.06em;margin:6px 0 26px}
.orbit{position:relative;aspect-ratio:1;max-width:420px;margin-left:auto}
.orbit svg{width:100%;height:100%;display:block}

/* page hero (subpages) */
.page-hero{padding:64px 0 44px;display:grid;grid-template-columns:1.2fr .8fr;gap:44px;align-items:end;border-bottom:1px solid var(--line)}
.page-hero h1{font-size:clamp(40px,5.4vw,70px);line-height:.96;letter-spacing:-.05em;margin:6px 0 18px}
.note{background:var(--navy);color:#fff;border-radius:var(--radius);padding:24px;border-top:4px solid var(--blue)}
.note strong{display:block;font-size:18px;margin-bottom:6px}
.note p{color:#c6d0e3;font-size:14px}

/* sections */
section{padding:72px 0;border-top:1px solid var(--line)}
.page-hero+section{border-top:0}
section h2{font-size:clamp(34px,4.6vw,58px);line-height:1;letter-spacing:-.045em;margin:0 0 22px}
.grid{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}
.grid.two{grid-template-columns:repeat(2,1fr)}
.card{position:relative;display:block;padding:28px;border:1px solid var(--line);border-radius:var(--radius);background:var(--surface);text-decoration:none;transition:.18s ease}
a.card:hover{border-color:var(--line-2);box-shadow:0 14px 40px rgba(11,24,48,.08);transform:translateY(-2px)}
.card .tag{font-size:12px;font-weight:850;color:var(--blue);letter-spacing:.08em}
.card h3{font-size:22px;line-height:1.2;margin:16px 0 10px}
.card p{color:var(--muted)}
.card .more{position:absolute;right:22px;top:24px;color:var(--blue);font-weight:900}
.split{display:grid;grid-template-columns:1fr 1fr;gap:50px;align-items:start}
.split p{font-size:20px;color:var(--muted)}

/* agenda list (index) */
.agenda{display:grid;gap:10px}
.direction{display:grid;grid-template-columns:48px 1fr auto;gap:18px;align-items:center;padding:18px 20px;border:1px solid var(--line);border-radius:var(--radius-s);background:var(--surface);text-decoration:none;transition:.18s}
.direction:hover{border-color:var(--line-2);background:var(--sky-2)}
.direction .num{font:700 12px var(--mono);color:var(--blue)}
.direction strong{display:block;font-size:17px;font-weight:720}
.direction span{color:var(--muted);font-size:14px}
.direction .more{color:var(--blue);font-weight:900}

/* research page */
.topic{display:grid;grid-template-columns:.9fr 1.1fr;gap:50px;align-items:start}
.topic .question{font-size:clamp(22px,2.4vw,28px);line-height:1.3;letter-spacing:-.02em;font-weight:650;margin:0 0 14px}
.topic .lead{font-size:17px}
.facets{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}
.facet{background:var(--sky-2);border:1px solid var(--line);border-radius:var(--radius-s);padding:16px 18px}
.facet dt{font-size:11px;letter-spacing:.14em;text-transform:uppercase;color:var(--blue);font-weight:850;margin-bottom:8px}
.facet dd{margin:0;color:var(--muted);font-size:14px}
.topic-nav{display:flex;gap:8px;flex-wrap:wrap;margin-top:22px}
.topic-nav a{text-decoration:none;font-size:13px;padding:8px 12px;border:1px solid var(--line);border-radius:999px;background:var(--surface);color:var(--navy)}
.topic-nav a:hover{border-color:var(--blue);color:var(--blue)}

/* callout / contact */
.callout{background:var(--navy);color:#fff;padding:42px;border-radius:24px;display:grid;grid-template-columns:1fr auto;gap:24px;align-items:center}
.callout .label{color:#8eb0ff}
.callout h2{margin:0}
.callout p{color:#c6d0e3;margin:12px 0 0;max-width:640px}
.callout .actions{margin-top:0}

/* network panels, counts, and the collaboration router */
[hidden]{display:none!important}
.net-panel{grid-column:1/-1;margin-top:26px;border:1px solid var(--line);border-radius:var(--radius);background:var(--surface);padding:18px 20px}
.net-head{display:flex;justify-content:space-between;align-items:baseline;gap:12px;flex-wrap:wrap}
.net-head .label{margin:0}
.net-count{font:600 12px var(--mono);color:var(--muted)}
.net-list{list-style:none;margin:12px 0 0;padding:0;display:grid;gap:2px}
.net-list a{display:grid;gap:2px;padding:10px 12px;margin:0 -12px;border-radius:10px;text-decoration:none;color:var(--navy);font-weight:650}
.net-list a:hover{background:var(--sky-2)}
.net-list span{font:700 10px/1 var(--mono);letter-spacing:.1em;text-transform:uppercase;color:var(--blue)}
.hub-pills{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}
.hub-pill{font-size:13px;font-weight:650;padding:7px 12px;border-radius:999px;border:1px solid var(--line);background:var(--white);text-decoration:none;color:var(--navy)}
.hub-pill:hover{border-color:var(--blue);color:var(--blue)}
.net-stats{margin:-28px 0 56px}
.net-stat-row{display:grid;grid-template-columns:repeat(4,1fr);gap:10px}
.net-stat{display:block;border:1px solid var(--line);border-radius:var(--radius-s);background:var(--surface);padding:16px 18px;text-decoration:none;color:var(--navy);transition:.15s}
.net-stat:hover{border-color:var(--blue)}
.net-stat strong{display:block;font-size:28px;line-height:1;letter-spacing:-.04em}
.net-stat span{display:block;margin-top:6px;font-size:13px;color:var(--muted)}
.router{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}
.route{display:flex;flex-direction:column;gap:8px;padding:22px;border:1px solid var(--line);border-radius:var(--radius);background:var(--surface);text-decoration:none;color:var(--navy);transition:.18s ease}
.route:hover{border-color:var(--blue);box-shadow:0 14px 40px rgba(11,24,48,.08);transform:translateY(-2px)}
.route strong{font-size:19px;line-height:1.25;letter-spacing:-.01em}
.route>span{font-size:14.5px;color:var(--muted)}
.route .route-kind{font:700 10.5px/1 var(--mono);letter-spacing:.12em;text-transform:uppercase;color:var(--blue)}
.route .route-go{margin-top:auto;padding-top:6px;font-size:13.5px;font-weight:750;color:var(--blue)}
.route:first-child{grid-row:span 2;justify-content:flex-start;background:var(--navy);color:#fff;border-color:var(--navy)}
.route:first-child>span{color:#c6d0e3}
.route:first-child .route-kind,.route:first-child .route-go{color:#8eb0ff}
@media(max-width:900px){.router{grid-template-columns:1fr 1fr}.route:first-child{grid-row:auto}.net-stat-row{grid-template-columns:repeat(2,1fr)}}
@media(max-width:560px){.router{grid-template-columns:1fr}}

/* footer: the sibling-site network, then the base line */
footer{position:relative;z-index:1;max-width:var(--max);margin:auto;padding:40px var(--pad) 54px;color:var(--muted);font-size:14px;border-top:1px solid var(--line)}
footer a{text-decoration:none}
footer a:hover{color:var(--navy)}
.network-title{font:800 11px/1.3 var(--mono);letter-spacing:.14em;text-transform:uppercase;margin:0 0 14px}
.network{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(4,1fr);gap:10px}
.network a,.network .here{display:block;height:100%;padding:14px 16px;border:1px solid var(--line);border-radius:12px;transition:.18s ease}
.network a:hover{border-color:var(--line-2);background:var(--sky-2);color:inherit}
.network strong{display:block;color:var(--navy);font-size:14px;line-height:1.3}
.network span{display:block;font-size:13px;margin-top:3px}
.network .here{border-color:var(--blue);background:var(--sky-2)}
.network .here small{display:inline-block;margin-top:8px;font:700 10px/1 var(--mono);letter-spacing:.12em;text-transform:uppercase;color:var(--blue)}
.footer-base{display:flex;justify-content:space-between;gap:12px 20px;flex-wrap:wrap;margin-top:24px}
.links{display:flex;gap:16px;flex-wrap:wrap}
@media(max-width:900px){.network{grid-template-columns:repeat(2,1fr)}}
@media(max-width:520px){.network{grid-template-columns:1fr}}

/* responsive */
@media(max-width:900px){
  .hero{grid-template-columns:1fr;padding-top:60px;gap:40px}
  .orbit{max-width:320px;margin:0}
  .page-hero,.split,.topic{grid-template-columns:1fr;gap:24px}
  .page-hero{padding-top:44px}
  .grid,.grid.two{grid-template-columns:1fr}
  .facets{grid-template-columns:1fr}
}
@media(max-width:720px){
  .nav{padding:12px 16px}
  .nav-toggle{display:block}
  .nav nav{display:none;position:absolute;left:0;right:0;top:100%;flex-direction:column;align-items:stretch;gap:0;background:var(--white);border-bottom:1px solid var(--line);padding:6px 16px 14px}
  .nav nav.open{display:flex}
  .nav nav a{padding:12px 4px;border-bottom:1px solid var(--line);font-size:15px}
  .nav nav a[aria-current="page"]:after{display:none}
  .nav nav a.cta{margin-top:10px;justify-content:center;display:inline-flex;border-bottom:1px solid var(--navy)}
  main{padding:0 16px}
  .hero h1{font-size:clamp(42px,13vw,60px)}
  section{padding:52px 0}
  .direction{grid-template-columns:36px 1fr auto;gap:12px;padding:16px}
  .callout{grid-template-columns:1fr;padding:30px}
  footer{flex-direction:column;padding-left:16px;padding-right:16px}
}
@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important}html{scroll-behavior:auto}}