@import url('https://fonts.googleapis.com/css2?family=Playfair+Display:ital,wght@1,600;1,700;1,800&display=swap');
/* ═══════════════════════════════════════════════════════════════
   air.css — shared Air design system for Cognivia deep-dive pages
   (The Science / The System / Research / About / FAQ).
   Mirrors landing.html exactly: cobalt night-sky canvas, Inter type,
   Anton display, Caveat cursive, ghost + haze buttons, flat frosted
   cards, hairline borders, underline links, scroll-in motion.
   ═══════════════════════════════════════════════════════════════ */
:root{
  --white:#ffffff; --haze:#f5f5f5; --ink:#1b1b1b;
  --twilight:#c3e2fb; --signal:#26dcf0; --navy:#0b3d66;
  --sky-1:#54d6f7; --sky-2:#3b8ef7; --sky-3:#2264d6; --sky-4:#134b93;
  --line:rgba(255,255,255,0.14); --line-soft:rgba(255,255,255,0.09);
  --muted:#a9c4e0; --muted-2:#d0e2f4;
  --font:'Inter',ui-sans-serif,system-ui,-apple-system,'Segoe UI',Roboto,sans-serif;
  --display:'Anton',Impact,sans-serif;
  --cursive:'Caveat',cursive;
  --maxw:1150px; --readw:760px; --nav-h:72px;
  --ease:cubic-bezier(0.22,0.61,0.36,1);
}
html[lang="hi"]{ --font:'Noto Sans Devanagari',ui-sans-serif,system-ui,sans-serif; }
html[lang="hi"] .display{ font-family:'Noto Sans Devanagari',sans-serif; font-weight:800; }
/* Devanagari needs more leading than Latin at the same optical size. */
html[lang="hi"] .prose, html[lang="hi"] .lede, html[lang="hi"] .faq-a, html[lang="hi"] p, html[lang="hi"] li, html[lang="hi"] .tl-item p, html[lang="hi"] .mech p, html[lang="hi"] .list-item p{ line-height:1.85; }

*{ box-sizing:border-box; }
html{ scroll-behavior:smooth; scroll-padding-top:calc(var(--nav-h) + 34px); -webkit-text-size-adjust:100%; }
body{ margin:0; background:var(--navy); color:var(--white); font-family:-apple-system,BlinkMacSystemFont,"SF Pro Text","Segoe UI",Roboto,Helvetica,Arial,sans-serif; font-weight:400; font-size:16px; line-height:1.5; -webkit-font-smoothing:antialiased; text-rendering:optimizeLegibility; overflow-x:hidden; }
a{ color:inherit; text-decoration:none; }
p{ margin:0; }
img,svg{ max-width:100%; }
::selection{ background:rgba(56,205,240,0.3); color:#fff; }

.wrap{ width:100%; max-width:var(--maxw); margin:0 auto; padding:0 24px; }
.readw{ max-width:var(--readw); }
.display{ font-family:var(--display); font-weight:400; text-transform:uppercase; letter-spacing:0.004em; line-height:0.9; }
.cursive{ font-family:var(--cursive); text-transform:none; font-style:italic; font-weight:600; letter-spacing:0; color:var(--twilight); }
.eyebrow{ font-size:13px; font-weight:600; letter-spacing:0.18em; text-transform:uppercase; color:var(--twilight); }

/* Buttons */
.btn{ display:inline-flex; align-items:center; gap:8px; font-family:var(--font); font-weight:500; font-size:15px; line-height:1; padding:12px 20px; border-radius:8px; cursor:pointer; border:1px solid transparent; transition:transform .18s var(--ease), background .18s var(--ease), border-color .18s var(--ease), box-shadow .18s var(--ease); text-decoration:none; white-space:nowrap; }
.btn:active{ opacity:0.92; }
.btn-haze{ background:var(--white); color:var(--ink); border-color:var(--white); }
.btn-haze:hover{  }
.btn-ghost{ background:transparent; color:var(--white); border-color:rgba(255,255,255,0.5); }
.btn-ghost:hover{ border-color:#fff; background:rgba(255,255,255,0.06); }
.btn-lg{ padding:15px 26px; font-size:16px; }
.link-u{ color:var(--signal); text-decoration:underline; text-underline-offset:3px; text-decoration-thickness:1.5px; }
.link-u:hover{ text-decoration-thickness:2px; }

/* Nav — floating rounded island, detached from the top (the OG Cognivia nav) */
.nav{ position:sticky; top:14px; z-index:50; width:calc(100% - 32px); max-width:var(--maxw); margin:14px auto 0; height:var(--nav-h); display:flex; align-items:center; background:rgba(11,61,102,0.82); backdrop-filter:blur(16px) saturate(1.35); -webkit-backdrop-filter:blur(16px) saturate(1.35); border:1px solid var(--line); border-radius:16px; box-shadow:0 10px 34px rgba(4,20,40,0.28); transition:background .4s var(--ease), border-color .4s var(--ease), box-shadow .4s var(--ease); }
.nav.scrolled{ background:rgba(9,48,82,0.94); border-color:rgba(255,255,255,0.22); box-shadow:0 14px 40px rgba(4,20,40,0.42); }
.nav .wrap{ display:flex; align-items:center; justify-content:flex-start; gap:34px; }
/* Serif-italic "glass" wordmark with a running light sheen — the old Cognivia logo. */
.brand{ font-family:'Playfair Display', Georgia, serif; font-style:italic; font-weight:700; font-size:24px; letter-spacing:0; display:inline-flex; align-items:baseline; gap:1px;
  background:linear-gradient(105deg,#dffdf6 0%,#ffffff 28%,#7fecd8 50%,#ffffff 72%,#dffdf6 100%);
  background-size:220% auto; -webkit-background-clip:text; background-clip:text;
  -webkit-text-fill-color:transparent; color:transparent; animation:brandSheen 6.5s linear infinite; }
.brand .dot{ -webkit-text-fill-color:var(--signal); color:var(--signal); }
@keyframes brandSheen{ to{ background-position:-220% center; } }
@media (prefers-reduced-motion:reduce){ .brand{ animation:none; } }
.nav-links{ display:flex; align-items:center; gap:26px; margin-left:0; }
.nav-links a{ font-size:14.5px; font-weight:500; color:var(--muted-2); transition:color .16s; }
.nav-links a:hover,.nav-links a[aria-current="page"]{ color:#fff; }
.nav-right{ display:flex; align-items:center; gap:10px; margin-left:auto; }
.lang{ display:inline-flex; border:1px solid rgba(255,255,255,0.22); border-radius:8px; overflow:hidden; }
.lang button{ background:transparent; border:none; color:var(--muted); font-family:var(--font); font-size:13px; font-weight:500; padding:8px 11px; cursor:pointer; }
.lang button[aria-pressed="true"]{ background:rgba(255,255,255,0.12); color:#fff; }
.nav-toggle{ display:none; background:none; border:1px solid rgba(255,255,255,0.3); border-radius:8px; color:#fff; width:40px; height:40px; cursor:pointer; }

/* Page hero */
.page-hero{ position:relative; overflow:hidden; margin-top:calc(-1*(var(--nav-h) + 14px)); padding:calc(var(--nav-h) + 78px) 0 clamp(48px,8vh,84px); background:radial-gradient(130% 108% at 50% -8%, var(--sky-2) 0%, var(--sky-3) 34%, var(--sky-4) 60%, var(--navy) 100%); }
.page-hero::after{ content:''; position:absolute; inset:0; pointer-events:none; background:radial-gradient(50% 42% at 24% 12%, rgba(150,205,245,0.16), transparent 70%); animation:drift 26s ease-in-out infinite alternate; }
@keyframes drift{ from{transform:translate3d(0,0,0)} to{transform:translate3d(-2.5%,2%,0)} }
.page-hero .wrap{ position:relative; z-index:1; }
.page-hero h1{ margin:16px 0 0; max-width:20ch; }
.page-hero h1 .display{ display:block; font-size:clamp(2.8rem,7vw,5.8rem); color:#fff; }
.page-hero .lede{ margin:22px 0 0; max-width:60ch; font-size:clamp(1.05rem,1.8vw,1.3rem); color:var(--muted-2); line-height:1.55; }
.crumbs{ font-size:13px; color:var(--muted); display:flex; gap:8px; align-items:center; }
.crumbs a{ color:var(--muted); } .crumbs a:hover{ color:#fff; }

/* Section rhythm */
.band{ padding:clamp(48px,7vh,88px) 0; }
/* Atmospheric depth — subtle drifting blooms so the canvas has life, not flat blue */
body::before{ content:''; position:fixed; inset:0; z-index:-1; pointer-events:none;
  background:radial-gradient(55% 42% at 80% 8%, rgba(84,214,247,0.12), transparent 60%),
             radial-gradient(48% 40% at 12% 88%, rgba(59,142,247,0.12), transparent 62%);
  animation:bodyDrift 34s ease-in-out infinite alternate; }
@keyframes bodyDrift{ from{transform:translate3d(0,0,0)} to{transform:translate3d(-2.5%,2.5%,0)} }
@media (prefers-reduced-motion:reduce){ body::before{ animation:none; } }
.band-tight{ padding:clamp(36px,6vh,64px) 0; }
.sec-kicker{ font-size:12.5px; font-weight:600; letter-spacing:0.16em; text-transform:uppercase; color:var(--signal); margin:0 0 14px; }
.sec-title{ font-family:var(--font); font-weight:600; font-size:clamp(2rem,4.4vw,3.3rem); line-height:1.1; letter-spacing:-0.03em; margin:0 0 18px; color:#fff; max-width:22ch; }
.prose{ font-size:clamp(1rem,1.5vw,1.15rem); line-height:1.68; color:var(--muted-2); max-width:var(--readw); }
.prose + .prose{ margin-top:20px; }
.prose strong{ color:#fff; font-weight:600; }
.hairline{ height:1px; background:var(--line-soft); border:0; margin:0; }

/* Flat frosted card */
.card{ background:rgba(255,255,255,0.045); border:1px solid rgba(255,255,255,0.12); border-radius:14px; padding:28px; }
.card h3{ font-family:var(--font); font-weight:600; font-size:1.25rem; letter-spacing:-0.015em; margin:0 0 12px; color:#fff; }
.card p{ font-size:15.5px; line-height:1.6; color:var(--muted-2); }

/* Numbered "principle" blocks (Science) */
.principle{ display:grid; grid-template-columns:120px 1fr; gap:28px; align-items:start; padding:clamp(28px,4vh,44px) 0; border-top:1px solid var(--line-soft); }
.principle .p-mark{ font-family:var(--display); font-weight:400; font-size:clamp(2.6rem,5vw,4rem); color:var(--twilight); line-height:0.9; }
.principle h3{ font-family:var(--font); font-weight:600; font-size:clamp(1.6rem,3vw,2.3rem); letter-spacing:-0.02em; margin:0 0 14px; color:#fff; }
.principle .prose{ max-width:64ch; }
.principle .note{ margin-top:12px; font-size:14px; color:var(--muted); }

/* Feature grid (System) */
.grid{ display:grid; grid-template-columns:repeat(3,1fr); gap:20px; }
.grid-2{ display:grid; grid-template-columns:repeat(2,1fr); gap:20px; }
.mech{ background:rgba(255,255,255,0.045); border:1px solid rgba(255,255,255,0.12); border-radius:12px; padding:22px; transition:transform .4s var(--ease), box-shadow .4s var(--ease); }
.mech:hover{ border-color:rgba(255,255,255,0.22); }
.mech .m-tag{ font-family:var(--display); font-size:12px; letter-spacing:0.14em; color:var(--signal); }
.mech h3{ font-family:var(--font); font-weight:600; font-size:1.1rem; letter-spacing:-0.01em; margin:8px 0 8px; color:#fff; }
.mech p{ font-size:14.5px; line-height:1.55; color:var(--muted-2); }

/* Variable chips (Learning Genome) */
.vars{ display:grid; grid-template-columns:repeat(4,1fr); gap:14px; }
.vchip{ background:rgba(255,255,255,0.04); border:1px solid var(--line-soft); border-radius:10px; padding:16px; }
.vchip b{ display:block; font-size:15px; font-weight:600; color:#fff; margin-bottom:4px; }
.vchip span{ font-size:13px; color:var(--muted); }

/* Roadmap timeline (Research) */
.timeline{ border-left:1px solid var(--line); margin-left:8px; padding-left:28px; display:flex; flex-direction:column; gap:34px; }
.tl-item{ position:relative; }
.tl-item::before{ content:''; position:absolute; left:-35px; top:4px; width:11px; height:11px; border-radius:50%; background:var(--signal); box-shadow:0 0 0 4px var(--navy); }
.tl-when{ font-family:var(--display); font-size:13px; letter-spacing:0.1em; color:var(--twilight); text-transform:uppercase; }
.tl-item h3{ font-family:var(--font); font-weight:600; font-size:1.15rem; letter-spacing:-0.01em; margin:8px 0 8px; color:#fff; }
.tl-item p{ font-size:15px; line-height:1.58; color:var(--muted-2); max-width:60ch; }

/* Limitations / ambitions list */
.list{ display:flex; flex-direction:column; gap:0; }
.list-item{ padding:26px 0; border-top:1px solid var(--line-soft); }
.list-item h3{ font-family:var(--font); font-weight:600; font-size:clamp(1.15rem,2vw,1.4rem); letter-spacing:-0.015em; margin:0 0 12px; color:#fff; }
.list-item p{ font-size:16px; line-height:1.62; color:var(--muted-2); max-width:70ch; }

/* Stat row */
.statrow{ display:flex; gap:44px; flex-wrap:wrap; }
.statrow .stat b{ display:block; font-family:var(--display); font-weight:400; font-size:clamp(2rem,4.5vw,3rem); color:#fff; line-height:1; }
.statrow .stat span{ font-size:13px; letter-spacing:0.05em; color:var(--muted); text-transform:uppercase; }

/* FAQ accordion */
.faq{ border-top:1px solid var(--line-soft); }
.faq details{ border-bottom:1px solid var(--line-soft); padding:6px 0; }
.faq summary{ list-style:none; cursor:pointer; padding:20px 44px 20px 4px; position:relative; font-weight:600; font-size:clamp(1.05rem,1.8vw,1.2rem); color:#fff; }
.faq summary::-webkit-details-marker{ display:none; }
.faq summary::after{ content:'+'; position:absolute; right:8px; top:50%; transform:translateY(-50%); font-weight:400; font-size:1.4rem; color:var(--twilight); transition:transform .25s var(--ease); }
.faq details[open] summary::after{ content:'–'; }
.faq .faq-a{ padding:0 4px 24px; font-size:16px; line-height:1.65; color:var(--muted-2); max-width:72ch; }

/* Author signature (About) */
.sig{ font-family:var(--cursive); font-style:italic; font-size:1.6rem; color:var(--twilight); }

/* Footer */
.foot{ border-top:1px solid var(--line-soft); padding:56px 0 40px; }
.foot .cols{ display:grid; grid-template-columns:1.6fr 1fr 1fr 1fr; gap:36px; }
.foot .fbrand{ font-family:var(--font); font-weight:700; font-size:22px; color:#fff; }
.foot .fbrand .dot{ color:var(--signal); }
.foot .ftag{ margin-top:12px; font-size:15px; color:var(--muted); max-width:34ch; line-height:1.55; }
.foot h5{ font-size:12px; letter-spacing:0.14em; text-transform:uppercase; color:var(--muted); margin:0 0 16px; font-weight:600; }
.foot ul{ list-style:none; margin:0; padding:0; display:flex; flex-direction:column; gap:11px; }
.foot ul a{ font-size:14.5px; color:var(--muted-2); }
.foot ul a:hover{ color:#fff; }
.foot .fbot{ margin-top:44px; padding-top:22px; border-top:1px solid var(--line-soft); display:flex; justify-content:space-between; flex-wrap:wrap; gap:12px; font-size:13px; color:var(--muted); }

/* Scroll reveal */
.reveal{ opacity:0; transform:translateY(26px); filter:blur(6px); transition:opacity .85s var(--ease), transform .85s var(--ease), filter .85s var(--ease); }
.reveal.in{ opacity:1; transform:none; filter:none; }
.stagger > *{ opacity:0; transform:translateY(22px); filter:blur(5px); transition:opacity .7s var(--ease), transform .7s var(--ease), filter .7s var(--ease); }
.stagger.in > *{ opacity:1; transform:none; filter:none; }
.stagger.in > *:nth-child(1){ transition-delay:.04s } .stagger.in > *:nth-child(2){ transition-delay:.12s }
.stagger.in > *:nth-child(3){ transition-delay:.20s } .stagger.in > *:nth-child(4){ transition-delay:.28s }
.stagger.in > *:nth-child(5){ transition-delay:.36s } .stagger.in > *:nth-child(6){ transition-delay:.44s }
.stagger.in > *:nth-child(7){ transition-delay:.50s } .stagger.in > *:nth-child(8){ transition-delay:.56s }

/* Lang visibility */
html[lang="en"] .hi{ display:none; } html[lang="hi"] .en{ display:none; }

@media (prefers-reduced-motion:reduce){
  .reveal,.stagger > *{ opacity:1 !important; transform:none !important; filter:none !important; transition:none !important; }
  .page-hero::after{ animation:none; }
}
@media (max-width:860px){
  .nav-links{ display:none; } .nav-toggle{ display:inline-flex; align-items:center; justify-content:center; }
  .grid,.grid-2,.vars{ grid-template-columns:1fr; }
  .principle{ grid-template-columns:1fr; gap:10px; }
  .foot .cols{ grid-template-columns:1fr 1fr; } .foot .fbrandcol{ grid-column:1 / -1; }
}
.nav-drawer{ display:none; }
.nav-drawer.open{ display:block; position:fixed; inset:calc(var(--nav-h) + 22px) 0 0; z-index:45; background:var(--navy); padding:24px; }
.nav-drawer a{ display:block; padding:16px 4px; font-size:20px; font-weight:500; border-bottom:1px solid var(--line-soft); color:#fff; }

/* ── Nav premium refinement (Air-style): sign-in as text link, minimal lang ── */
.nav .btn-ghost{ border-color:transparent !important; background:transparent !important; padding-left:6px; padding-right:6px; font-weight:500; }
.nav .btn-ghost:hover{ transform:none; color:#fff; }
.nav .lang{ border-color:transparent; background:transparent; }
.nav .lang button[aria-pressed="true"]{ background:transparent; color:#fff; text-decoration:underline; text-underline-offset:4px; text-decoration-color:var(--signal); }
.nav .btn-haze{ border-radius:9px; padding:11px 22px; }
.nav-links a{ font-size:15px; }

/* Language link (one locale per URL; replaces the old EN/HI toggle) */
.lang{ border:none !important; background:transparent !important; }
.lang-link{ font-family:var(--font); font-size:13px; font-weight:500; color:var(--muted); text-decoration:none; padding:8px 12px; border:1px solid rgba(255,255,255,0.22); border-radius:8px; transition:color .16s var(--ease), border-color .16s var(--ease); }
.lang-link:hover{ color:#fff; border-color:rgba(255,255,255,0.55); }