/* ==========================================================================
   Luc Dumont — Ad Tech Knowledge Base
   Design language: precise technical reference. Cool paper, ink, one electric
   indigo signal accent, mono utility labels, serif reading surface.
   ========================================================================== */

:root{
  --paper:#F5F6F8;
  --surface:#FFFFFF;
  --ink:#0D1017;
  --slate:#5A6474;
  --slate-2:#8A93A1;
  --line:#E3E6EB;
  --line-2:#EEF0F3;
  --accent:#2338E8;
  --accent-ink:#1526B0;
  --accent-soft:#EAEDFF;
  --good:#0B7A5B;
  --maxw:1120px;
  --readw:720px;
  --r:10px;
}

*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:"Newsreader",Georgia,"Times New Roman",serif;
  font-size:19px;
  line-height:1.62;
  font-optical-sizing:auto;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--accent);text-decoration:none}
a:hover{color:var(--accent-ink);text-decoration:underline;text-underline-offset:2px}
img{max-width:100%;height:auto}

.wrap{max-width:var(--maxw);margin:0 auto;padding:0 24px}
.mono{font-family:"IBM Plex Mono",ui-monospace,SFMono-Regular,Menlo,monospace}
.eyebrow{
  font-family:"IBM Plex Mono",monospace;
  font-size:12px;letter-spacing:.14em;text-transform:uppercase;
  color:var(--slate);font-weight:500;
}

/* ---- Skip link + focus ---- */
.skip{position:absolute;left:-999px}
.skip:focus{left:12px;top:12px;background:var(--ink);color:#fff;padding:8px 12px;border-radius:6px;z-index:99}
:focus-visible{outline:3px solid var(--accent);outline-offset:2px;border-radius:4px}

/* ---- Header / nav ---- */
.site-header{
  background:#0a0a0f;
  border-bottom:1px solid #2a2a38;
  position:sticky;top:0;z-index:40;
}
.site-header-bar{background:#e50914;height:2px}
.nav{display:flex;align-items:center;justify-content:space-between;height:64px;gap:20px}
.brand{
  font-family:"Space Grotesk",system-ui,sans-serif;
  font-weight:700;font-size:18px;letter-spacing:-.01em;color:#fff;
  display:flex;align-items:center;gap:10px;white-space:nowrap;
}
.brand:hover{text-decoration:none;color:#fff}
.brand-icon{
  width:32px;height:32px;background:#e50914;border-radius:6px;
  display:flex;align-items:center;justify-content:center;flex:none;color:#fff;
}
.nav-links{display:flex;gap:4px;align-items:center;font-family:"Space Grotesk",sans-serif;font-size:14px}
.nav-links a{color:#8b8b9a;font-weight:500;padding:6px 12px;border-radius:6px;transition:color .2s,background .2s}
.nav-links a:hover{color:#fff;background:rgba(255,255,255,.05);text-decoration:none}
.nav-links a.active{color:#fff;background:rgba(255,255,255,.1)}
.nav-cta{
  font-family:"Space Grotesk",sans-serif;font-size:14px;font-weight:600;
  background:#e50914;color:#fff;padding:8px 16px;border-radius:6px;white-space:nowrap;
  transition:background .2s;
}
.nav-cta:hover{background:#c0070f;text-decoration:none;color:#fff}
@media(max-width:768px){.nav-links{display:none}.nav-cta{display:none}}

/* ---- Breadcrumb ---- */
.crumbs{font-family:"IBM Plex Mono",monospace;font-size:12.5px;color:var(--slate-2);padding:18px 0 0}
.crumbs a{color:var(--slate);text-decoration:none}
.crumbs a:hover{color:var(--accent)}
.crumbs span{color:var(--line);margin:0 8px}

/* ---- Supply-chain rail (the signature element) ---- */
.rail{
  margin:20px 0 4px;padding:16px 18px;background:var(--surface);
  border:1px solid var(--line);border-radius:var(--r);
  display:flex;flex-direction:column;gap:12px;
}
.rail-head{display:flex;justify-content:space-between;align-items:baseline;gap:12px;flex-wrap:wrap}
.rail-head .label{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.14em;text-transform:uppercase;color:var(--slate-2)}
.rail-track{display:flex;align-items:stretch;gap:0;flex-wrap:wrap}
.node{
  flex:1 1 0;min-width:76px;text-align:center;position:relative;
  font-family:"IBM Plex Mono",monospace;font-size:11.5px;letter-spacing:.03em;
  color:var(--slate-2);padding:10px 6px;border:1px solid var(--line);
  border-right:0;background:var(--paper);
}
.node:first-child{border-radius:8px 0 0 8px}
.node:last-child{border-right:1px solid var(--line);border-radius:0 8px 8px 0}
.node.on{background:var(--accent);color:#fff;border-color:var(--accent);font-weight:600;z-index:1}
.node.on + .node{border-left-color:var(--accent)}
.rail-note{font-family:"Space Grotesk",sans-serif;font-size:13px;color:var(--slate)}
.layer-tag{
  align-self:flex-start;font-family:"IBM Plex Mono",monospace;font-size:11px;
  letter-spacing:.1em;text-transform:uppercase;background:var(--accent-soft);
  color:var(--accent-ink);padding:4px 9px;border-radius:5px;
}
@media(max-width:560px){.node{min-width:44px;font-size:9.5px;padding:8px 3px}}

/* ---- Article layout ---- */
.layout{display:grid;grid-template-columns:1fr 260px;gap:56px;padding:40px 0 72px;align-items:start}
@media(max-width:920px){.layout{grid-template-columns:1fr;gap:0}}
article{max-width:var(--readw)}
.hero h1{
  font-family:"Space Grotesk",sans-serif;font-weight:700;
  font-size:clamp(30px,5vw,46px);line-height:1.06;letter-spacing:-.02em;
  margin:14px 0 0;
}
.lede{font-size:22px;line-height:1.5;color:var(--ink);margin:20px 0 0}
.lede b,.lede strong{font-weight:600}
.meta-row{
  display:flex;gap:18px;flex-wrap:wrap;margin:22px 0 0;padding:14px 0;
  border-top:1px solid var(--line);border-bottom:1px solid var(--line);
  font-family:"IBM Plex Mono",monospace;font-size:12px;color:var(--slate);
}
.meta-row b{color:var(--ink);font-weight:600}

/* ---- Key takeaways ---- */
.tldr{
  margin:34px 0;padding:22px 24px;background:var(--surface);
  border:1px solid var(--line);border-left:3px solid var(--accent);border-radius:var(--r);
}
.tldr h2{font-family:"Space Grotesk",sans-serif;font-size:13px;letter-spacing:.1em;
  text-transform:uppercase;color:var(--slate);margin:0 0 12px;font-weight:600}
.tldr ul{margin:0;padding-left:20px}
.tldr li{margin:8px 0;font-size:17.5px;line-height:1.5}

/* ---- Body prose ---- */
.prose h2{font-family:"Space Grotesk",sans-serif;font-size:26px;font-weight:600;
  letter-spacing:-.01em;margin:44px 0 4px}
.prose h3{font-family:"Space Grotesk",sans-serif;font-size:19px;font-weight:600;margin:28px 0 2px}
.prose p{margin:14px 0}
.prose ul,.prose ol{margin:14px 0;padding-left:22px}
.prose li{margin:7px 0}
.prose strong{font-weight:600}

/* ---- Facts table ---- */
.facts{margin:26px 0;border:1px solid var(--line);border-radius:var(--r);overflow:hidden;background:var(--surface)}
.facts table{border-collapse:collapse;width:100%;font-size:16px}
.facts th,.facts td{text-align:left;padding:12px 16px;border-bottom:1px solid var(--line-2);vertical-align:top}
.facts tr:last-child th,.facts tr:last-child td{border-bottom:0}
.facts th{font-family:"Space Grotesk",sans-serif;font-weight:600;color:var(--ink);width:38%;background:var(--paper)}
.facts td{color:var(--slate);font-family:"Newsreader",serif}

/* ---- FAQ ---- */
.faq{margin:44px 0 0}
.faq h2{font-family:"Space Grotesk",sans-serif;font-size:26px;font-weight:600;margin:0 0 6px}
details{border-bottom:1px solid var(--line);padding:4px 0}
summary{cursor:pointer;list-style:none;padding:16px 30px 16px 0;position:relative;
  font-family:"Space Grotesk",sans-serif;font-weight:600;font-size:18px;color:var(--ink)}
summary::-webkit-details-marker{display:none}
summary::after{content:"+";position:absolute;right:2px;top:14px;font-family:"IBM Plex Mono",monospace;
  color:var(--accent);font-size:22px;transition:transform .2s ease}
details[open] summary::after{content:"−"}
.faq-a{padding:0 0 18px;color:var(--slate);font-size:17.5px}
.faq-a p{margin:0 0 10px}

/* ---- Expert note ---- */
.expert{
  margin:44px 0;padding:24px 26px;background:linear-gradient(180deg,var(--accent-soft),#fff);
  border:1px solid #D6DBFF;border-radius:var(--r);
}
.expert .tag{font-family:"IBM Plex Mono",monospace;font-size:11px;letter-spacing:.12em;
  text-transform:uppercase;color:var(--accent-ink)}
.expert p{margin:10px 0 0;font-size:18px;line-height:1.55;font-style:italic}
.expert .by{margin-top:14px;font-style:normal;font-family:"Space Grotesk",sans-serif;
  font-size:14px;color:var(--slate)}
.expert .by b{color:var(--ink)}

/* ---- Related ---- */
.related{margin:48px 0 0}
.related h2{font-family:"Space Grotesk",sans-serif;font-size:15px;letter-spacing:.08em;
  text-transform:uppercase;color:var(--slate);margin:0 0 14px;font-weight:600}
.related-grid{display:grid;grid-template-columns:1fr 1fr;gap:12px}
@media(max-width:560px){.related-grid{grid-template-columns:1fr}}
.rel-card{display:block;padding:14px 16px;border:1px solid var(--line);border-radius:var(--r);
  background:var(--surface)}
.rel-card:hover{border-color:var(--accent);text-decoration:none}
.rel-card .k{font-family:"IBM Plex Mono",monospace;font-size:11px;color:var(--slate-2)}
.rel-card .t{font-family:"Space Grotesk",sans-serif;font-weight:600;color:var(--ink);
  font-size:16px;margin-top:3px}

/* ---- Sidebar ---- */
.aside{position:sticky;top:88px;font-family:"Space Grotesk",sans-serif}
@media(max-width:920px){.aside{position:static;margin:8px 0 40px}}
.author-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--r);padding:20px}
.author-card .who{font-weight:700;font-size:17px}
.author-card .role{color:var(--slate);font-size:13.5px;margin-top:2px;line-height:1.4}
.author-card .bio{font-family:"Newsreader",serif;font-size:15px;color:var(--slate);margin:12px 0 0;line-height:1.5}
.author-card .cta{display:inline-block;margin-top:14px;background:var(--ink);color:#fff;
  padding:9px 15px;border-radius:8px;font-size:14px;font-weight:600}
.author-card .cta:hover{background:var(--accent);text-decoration:none}
.toc{margin-top:20px;border-top:1px solid var(--line);padding-top:18px}
.toc .lbl{font-size:11px;letter-spacing:.1em;text-transform:uppercase;color:var(--slate-2)}
.toc a{display:block;color:var(--slate);font-size:14px;padding:6px 0;font-weight:500}
.toc a:hover{color:var(--accent);text-decoration:none}

/* ---- Hub / index pages ---- */
.hub-hero{padding:56px 0 30px;border-bottom:1px solid var(--line)}
.hub-hero h1{font-family:"Space Grotesk",sans-serif;font-weight:700;
  font-size:clamp(34px,6vw,60px);line-height:1.02;letter-spacing:-.025em;margin:16px 0 0}
.hub-hero .lede{max-width:660px}
.cluster{padding:44px 0;border-bottom:1px solid var(--line)}
.cluster-head{display:flex;align-items:baseline;gap:14px;margin-bottom:6px}
.cluster-head h2{font-family:"Space Grotesk",sans-serif;font-size:28px;font-weight:700;
  letter-spacing:-.01em;margin:0}
.cluster-head .n{font-family:"IBM Plex Mono",monospace;color:var(--accent);font-size:14px}
.cluster p.sub{color:var(--slate);margin:0 0 20px;max-width:640px}
.card-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:14px}
@media(max-width:820px){.card-grid{grid-template-columns:1fr 1fr}}
@media(max-width:520px){.card-grid{grid-template-columns:1fr}}
.topic-card{display:block;background:var(--surface);border:1px solid var(--line);
  border-radius:var(--r);padding:18px 18px 16px;transition:border-color .15s ease,transform .15s ease}
.topic-card:hover{border-color:var(--accent);transform:translateY(-2px);text-decoration:none}
.topic-card .abbr{font-family:"IBM Plex Mono",monospace;font-size:11px;color:var(--slate-2);letter-spacing:.04em}
.topic-card .name{font-family:"Space Grotesk",sans-serif;font-weight:600;font-size:18px;
  color:var(--ink);margin:6px 0 6px;letter-spacing:-.01em}
.topic-card .desc{font-family:"Newsreader",serif;font-size:15px;color:var(--slate);line-height:1.45}

/* ---- Footer ---- */
.site-footer{background:var(--ink);color:#B9C0CC;margin-top:0;padding:48px 0 40px;
  font-family:"Space Grotesk",sans-serif;font-size:14px}
.site-footer a{color:#D7DCE6}
.site-footer .cols{display:grid;grid-template-columns:2fr 1fr 1fr;gap:32px}
@media(max-width:720px){.site-footer .cols{grid-template-columns:1fr}}
.site-footer h4{color:#fff;font-size:12px;letter-spacing:.1em;text-transform:uppercase;margin:0 0 12px}
.site-footer .foot-brand{font-weight:700;color:#fff;font-size:18px}
.site-footer p{margin:8px 0;line-height:1.5;max-width:340px}
.site-footer .fnav a{display:block;color:#B9C0CC;padding:4px 0}
.site-footer .fnav a:hover{color:#fff}
.site-footer .fine{margin-top:32px;padding-top:20px;border-top:1px solid #232733;
  color:#7A828F;font-size:12.5px;display:flex;justify-content:space-between;gap:16px;flex-wrap:wrap}

@media(prefers-reduced-motion:reduce){
  *{transition:none!important;animation:none!important}
}