/* concept.css — the MAIN-SITE skin for /concepts/ pages.
   Replaces the insights article shell (insights.css / .topbar / .post). Reuses the site design
   tokens from _ds/colors_and_type.css and mirrors the homepage chrome (.bar / .nav / footer /
   backdrop / grain) so a concept page reads as a core site page, not a blog post. */

*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth}
body{background:var(--bg);color:var(--ink);font-family:var(--font-sans);-webkit-font-smoothing:antialiased;overflow-x:hidden}
::selection{background:rgba(94,230,208,.22)}
:root[data-theme="light"] ::selection{background:rgba(14,124,110,.18)}
a{color:inherit;text-decoration:none}

/* ---- backdrop + filmic grain (site signature; no 3D cost on a reading page) ---- */
#bgfall{position:fixed;inset:0;z-index:0;background:var(--bg-fall)}
body::after{content:"";position:fixed;inset:0;pointer-events:none;z-index:60;opacity:.04;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='120' height='120'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.9' numOctaves='2'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E")}
:root[data-theme="light"] body::after{opacity:.025}

/* ---- top bar (identical treatment to the homepage) ---- */
.bar{position:fixed;top:0;left:0;right:0;z-index:40;display:flex;justify-content:space-between;align-items:center;
  padding:22px 38px;background:rgba(5,6,10,.72);backdrop-filter:blur(14px);-webkit-backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}
:root[data-theme="light"] .bar{background:rgba(251,250,247,.82)}
.brand{font-family:var(--font-sans);font-weight:700;font-size:23px;letter-spacing:-.022em;color:#fff}
:root[data-theme="light"] .brand{color:var(--ink)}
.brand .io{background:linear-gradient(95deg,#ef4444,#f97316);-webkit-background-clip:text;background-clip:text;color:transparent}
.nav{display:flex;gap:30px;align-items:center;font-family:var(--font-mono);font-size:11px;letter-spacing:.16em;text-transform:uppercase;color:var(--muted)}
.nav a{cursor:pointer;transition:color .25s}
.nav a:hover,.nav a.here{color:var(--ink)}
.themebtn{display:flex;align-items:center;justify-content:center;width:34px;height:34px;border:1px solid var(--line-2);border-radius:var(--r-xs);color:var(--muted);cursor:pointer;background:transparent;transition:.25s;flex-shrink:0}
.themebtn:hover{color:var(--ink);border-color:var(--signal)}
.themebtn svg{width:15px;height:15px;display:block}
.themebtn .moon{display:none}
:root[data-theme="light"] .themebtn .sun{display:none}
:root[data-theme="light"] .themebtn .moon{display:block}

/* ---- hero ---- */
.c-hero{position:relative;z-index:2;padding:150px 38px 58px;overflow:hidden}
.c-hero .hero-canvas{position:absolute;inset:0;z-index:-1;width:100%;height:100%;opacity:.42;
  -webkit-mask-image:linear-gradient(90deg,#000 0%,rgba(0,0,0,.4) 55%,transparent 78%);
  mask-image:linear-gradient(90deg,#000 0%,rgba(0,0,0,.4) 55%,transparent 78%)}
.c-hero .inner{position:relative;max-width:1120px;margin:0 auto}
.c-eyebrow{font-family:var(--font-mono);font-size:11px;letter-spacing:.2em;text-transform:uppercase;color:var(--signal);margin-bottom:22px}
.c-hero h1{font-family:var(--font-serif);font-weight:300;font-size:clamp(34px,5vw,60px);line-height:1.06;letter-spacing:-.02em;color:var(--ink);max-width:16ch}
.c-hero h1 em{font-style:italic;color:var(--signal)}
.c-deck{font-family:var(--font-serif);font-style:italic;font-weight:300;font-size:clamp(18px,2vw,23px);line-height:1.45;color:var(--muted);margin-top:22px;max-width:42ch}

/* ---- reading body ---- */
.c-body{position:relative;z-index:2;background:var(--bg);border-top:1px solid var(--line);padding:68px 38px 40px}
.c-body .col{max-width:720px;margin:0 auto}
.c-body p{font-family:var(--font-serif);font-weight:400;font-size:19px;line-height:1.74;color:rgba(234,240,242,.9);margin-bottom:24px;letter-spacing:.002em}
:root[data-theme="light"] .c-body p{color:rgba(24,28,32,.86)}
.c-body h2{font-family:var(--font-serif);font-weight:400;font-size:clamp(23px,3vw,30px);letter-spacing:-.012em;color:var(--ink);margin:52px 0 16px}
.c-body strong{color:var(--ink);font-weight:600}
.c-body a{color:var(--signal);border-bottom:1px solid rgba(105,232,212,.4);transition:border-color .2s}
.c-body a:hover{border-color:var(--signal)}
.c-body .hedge{margin-top:44px;padding-top:26px;border-top:1px solid var(--line);font-family:var(--font-mono);font-size:11.5px;letter-spacing:.03em;color:var(--faint);line-height:1.75}

/* an auditable-number callout (keeps the rigour visible without a lecture) */
.c-figure{margin:34px 0;padding:24px 26px;border-left:2px solid var(--signal);background:var(--bg-2);border-radius:0 var(--r-lg) var(--r-lg) 0}
.c-figure p{font-family:var(--font-sans);font-size:15px;line-height:1.64;color:var(--muted);margin:0}
.c-figure b{color:var(--ink);font-weight:600}

/* ---- next: the other concepts + CTA ---- */
.c-next{position:relative;z-index:2;background:var(--bg);border-top:1px solid var(--line);padding:58px 38px 88px}
.c-next .col{max-width:1120px;margin:0 auto}
.c-next .nlab{font-family:var(--font-mono);font-size:11px;letter-spacing:.2em;text-transform:uppercase;color:var(--faint);margin-bottom:24px}
.c-cards{display:grid;grid-template-columns:1fr 1fr;gap:22px}
.c-cards.trio{grid-template-columns:repeat(3,1fr)}
.hub-intro{font-family:var(--font-serif);font-weight:400;font-size:20px;line-height:1.6;color:var(--muted);max-width:660px;margin-bottom:42px}

/* the "who it's for" door grid (shared page skin, used by /for/) */
.doors{display:grid;grid-template-columns:repeat(2,1fr);gap:16px;margin:40px 0 8px}
.door{display:block;background:var(--bg-2);border:1px solid var(--line);border-radius:var(--r-lg);padding:26px 28px;color:inherit;transition:.25s}
.door:hover{border-color:var(--line-2);background:var(--bg-3);transform:translateY(-2px)}
.door.wide{grid-column:1 / -1}
.door .de{font-family:var(--font-mono);font-size:10px;letter-spacing:.18em;text-transform:uppercase;color:var(--signal);margin-bottom:12px}
.door h3{font-family:var(--font-serif);font-weight:500;font-size:21px;letter-spacing:-.012em;color:var(--ink);margin-bottom:10px}
.door p{font-family:var(--font-sans);font-size:14px;line-height:1.62;color:var(--muted);margin:0}
.door .open{margin-top:14px;font-family:var(--font-mono);font-size:10.5px;letter-spacing:.08em;color:var(--faint)}
@media(max-width:720px){.doors{grid-template-columns:1fr}}
.c-card{display:block;padding:30px;border:1px solid var(--line);border-radius:var(--r-lg);background:var(--bg-2);transition:.25s;color:inherit}
.c-card:hover{border-color:var(--line-2);background:var(--bg-3);transform:translateY(-2px)}
.c-card .ct{font-family:var(--font-mono);font-size:10px;letter-spacing:.2em;text-transform:uppercase;color:var(--signal);margin-bottom:12px}
.c-card h3{font-family:var(--font-serif);font-weight:400;font-size:22px;letter-spacing:-.01em;margin-bottom:10px;color:var(--ink)}
.c-card p{font-size:13.5px;line-height:1.55;color:var(--muted)}
.c-cta{margin-top:40px;display:flex;flex-wrap:wrap;gap:16px;align-items:center}
.btn{font-family:var(--font-mono);font-size:12px;letter-spacing:.12em;text-transform:uppercase;padding:15px 26px;border:1px solid var(--ember);background:var(--ember);color:#1a0f02;cursor:pointer;border-radius:var(--r-xs);transition:.3s;font-weight:500}
.btn:hover{background:transparent;color:var(--ember);box-shadow:var(--glow-ember)}
.btn.ghost{background:transparent;border-color:var(--line-2);color:var(--ink)}
.btn.ghost:hover{border-color:var(--signal);color:var(--signal)}

/* ---- footer (identical to the homepage) ---- */
footer{position:relative;z-index:2;background:var(--bg);border-top:1px solid var(--line);padding:54px 38px 40px}
.foot{max-width:1120px;margin:0 auto;display:flex;justify-content:space-between;align-items:flex-start;flex-wrap:wrap;gap:24px}
.foot .brand2{font-family:var(--font-sans);font-weight:700;font-size:22px;letter-spacing:-.022em;color:var(--ink)}
.foot .brand2 .io{background:linear-gradient(95deg,#ef4444,#f97316);-webkit-background-clip:text;background-clip:text;color:transparent}
.foot .line{font-family:var(--font-serif);font-style:italic;font-weight:300;font-size:18px;color:var(--muted);margin-top:10px}
.foot .fnav{display:flex;gap:26px;flex-wrap:wrap;font-family:var(--font-mono);font-size:11px;letter-spacing:.12em;text-transform:uppercase;color:var(--faint)}
.foot .fnav a:hover{color:var(--ink)}
.copy{max-width:1120px;margin:40px auto 0;font-family:var(--font-mono);font-size:10.5px;letter-spacing:.1em;text-transform:uppercase;color:var(--faint)}

@media(max-width:860px){
  .nav{display:none}
  .bar{padding:18px 22px}
  .c-hero{padding:120px 22px 40px}
  .c-body,.c-next{padding-left:22px;padding-right:22px}
  .c-cards,.c-cards.trio{grid-template-columns:1fr}
  .foot{flex-direction:column}
}