:root{
  --primary:#475569;
  --secondary:#334155;
  --accent:#f59e0b;
  --bg:#ffffff;
  --surface:#f8fafc;
  --surface-alt:#f1f5f9;
  --text:#1e293b;
  --muted:#6b7280;
  --border:#cbd5e1;
  --row-alt:#f8fafc;
  --radius:12px;
  --shadow:0 6px 18px rgba(30,41,59,.08);
  --shadow-lg:0 14px 40px rgba(30,41,59,.14);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;padding:0;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  color:var(--text);
  background:var(--bg);
  line-height:1.65;
  font-size:17px;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--secondary);text-decoration:underline;text-decoration-color:var(--accent);text-underline-offset:3px}
a:hover{color:var(--accent)}
img{max-width:100%;height:auto;display:block}
.container{max-width:1080px;margin:0 auto;padding:0 20px}

/* --- Sticky gradient header --- */
.site-header{
  position:sticky;top:0;z-index:20;
  background:linear-gradient(90deg,var(--primary) 0%,var(--secondary) 100%);
  color:#f8fafc;
  box-shadow:var(--shadow);
}
.site-header .container{display:flex;align-items:center;justify-content:space-between;padding-top:12px;padding-bottom:12px;flex-wrap:wrap;gap:12px}
.brand{display:flex;align-items:center;gap:12px;color:#f8fafc;text-decoration:none}
.brand img{width:40px;height:40px;border-radius:8px;background:#fff;padding:3px}
.brand strong{font-size:1.15rem;letter-spacing:.3px}
.brand span{display:block;font-size:.75rem;color:#cbd5e1;font-weight:400}

nav.primary{display:flex;flex-wrap:wrap;gap:4px}
nav.primary a{
  color:#f1f5f9;text-decoration:none;
  padding:8px 12px;border-radius:8px;font-size:.94rem;
  transition:background .18s;
}
nav.primary a:hover{background:rgba(245,158,11,.22);color:#fff}
nav.primary a.active{background:var(--accent);color:#1e293b;font-weight:600}

/* --- Hero --- */
.hero{
  background:
    radial-gradient(circle at 15% 20%, rgba(245,158,11,.18), transparent 50%),
    radial-gradient(circle at 85% 80%, rgba(255,255,255,.12), transparent 55%),
    linear-gradient(135deg,var(--primary) 0%,var(--secondary) 60%,#0f172a 100%);
  color:#f8fafc;
  padding:56px 0 60px;
}
.hero h1{
  font-size:clamp(1.7rem,4vw,2.55rem);
  margin:0 0 12px;
  line-height:1.15;
  letter-spacing:-.5px;
}
.hero .byline{color:#cbd5e1;font-size:.94rem;margin:0 0 22px}
.hero .byline strong{color:#f59e0b}
.hero .intro p{font-size:1.06rem;margin:.5em 0;color:#f1f5f9;max-width:70ch}

.cta-row{margin-top:26px;display:flex;flex-wrap:wrap;gap:12px}
.btn{
  display:inline-block;padding:12px 22px;border-radius:10px;
  text-decoration:none;font-weight:600;font-size:.98rem;
  transition:transform .15s,box-shadow .15s;
}
.btn-primary{background:var(--accent);color:#1e293b;box-shadow:0 4px 14px rgba(245,158,11,.35)}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 6px 18px rgba(245,158,11,.5);color:#1e293b}
.btn-outline{background:transparent;color:#f8fafc;border:2px solid #f8fafc}
.btn-outline:hover{background:#f8fafc;color:var(--secondary)}

/* --- Main sections --- */
main{padding:40px 0 20px}
section{padding:14px 0}
h2{
  font-size:clamp(1.35rem,2.4vw,1.7rem);
  margin:36px 0 14px;
  padding:10px 16px;
  border-left:5px solid var(--accent);
  background:linear-gradient(90deg,var(--surface-alt) 0%, transparent 90%);
  border-radius:0 var(--radius) var(--radius) 0;
  color:var(--secondary);
  scroll-margin-top:96px;
}
h3{color:var(--secondary);margin:22px 0 8px;font-size:1.15rem}
p{margin:.55em 0}

/* --- Table of contents --- */
nav.toc{
  background:var(--surface);
  border:1px solid var(--border);
  border-left:5px solid var(--primary);
  padding:18px 22px;
  border-radius:var(--radius);
  margin:26px 0 18px;
}
nav.toc strong{display:block;color:var(--secondary);margin-bottom:8px;letter-spacing:.4px;font-size:.95rem;text-transform:uppercase}
nav.toc ol{margin:0;padding-left:22px;columns:2;column-gap:28px}
nav.toc ol li{margin:4px 0;break-inside:avoid}
nav.toc a{text-decoration:none;color:var(--secondary)}
nav.toc a:hover{color:var(--accent)}

/* --- Lists --- */
main ol{list-style:none;counter-reset:ol;padding-left:0}
main ol li{counter-increment:ol;position:relative;padding-left:44px;margin:.5em 0;min-height:28px}
main ol li::before{
  content:counter(ol);
  position:absolute;left:0;top:2px;
  width:28px;height:28px;border-radius:50%;
  background:var(--accent);color:#1e293b;
  font-weight:700;font-size:.85rem;
  display:flex;align-items:center;justify-content:center;
}
main ul{list-style:none;padding-left:0}
main ul li{position:relative;padding-left:26px;margin:.4em 0}
main ul li::before{
  content:"▸";position:absolute;left:0;top:0;
  color:var(--accent);font-weight:700;
}
nav.toc ol{list-style:decimal;counter-reset:none;padding-left:22px}
nav.toc ol li{padding-left:0;min-height:0}
nav.toc ol li::before{content:none}

/* --- Tables --- */
.table-wrap{overflow-x:auto;margin:20px 0;border-radius:var(--radius);border:1px solid var(--border);box-shadow:var(--shadow)}
table{width:100%;border-collapse:collapse;background:#fff}
thead th{
  background:linear-gradient(90deg,var(--primary),var(--secondary));
  color:#f8fafc;
  padding:14px 16px;text-align:left;font-weight:600;font-size:.94rem;
  letter-spacing:.3px;
}
tbody td{padding:12px 16px;border-bottom:1px solid var(--border);font-size:.96rem;vertical-align:top}
tbody tr:nth-child(even){background:var(--row-alt)}
tbody tr:last-child td{border-bottom:none}

/* --- Callouts --- */
.callout{
  background:linear-gradient(135deg,var(--surface),var(--surface-alt));
  border:1px solid var(--border);
  border-left:5px solid var(--accent);
  padding:18px 22px;
  border-radius:var(--radius);
  margin:22px 0;
}
.callout strong{color:var(--secondary)}

/* --- FAQ accordion --- */
details{
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  margin:10px 0;
  transition:box-shadow .18s;
}
details[open]{box-shadow:var(--shadow);border-color:var(--accent)}
details summary{
  cursor:pointer;
  padding:14px 46px 14px 18px;
  font-weight:600;
  color:var(--secondary);
  list-style:none;
  position:relative;
}
details summary::-webkit-details-marker{display:none}
details summary::after{
  content:"▼";
  position:absolute;right:18px;top:50%;
  transform:translateY(-50%);
  color:var(--accent);
  transition:transform .22s;
  font-size:.8rem;
}
details[open] summary::after{transform:translateY(-50%) rotate(-180deg)}
details .a{padding:0 18px 16px;color:var(--text)}

/* --- Author box --- */
.author-box{
  background:linear-gradient(135deg,var(--surface-alt),#e2e8f0);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:22px;
  display:flex;
  gap:20px;
  align-items:flex-start;
  margin:34px 0 12px;
  box-shadow:var(--shadow);
}
.author-box img{width:88px;height:88px;border-radius:50%;flex-shrink:0;border:3px solid var(--accent)}
.author-box h3{margin:0 0 6px;color:var(--secondary)}
.author-box p{margin:.3em 0;font-size:.96rem}
.author-box .role{color:var(--accent);font-weight:600;font-size:.9rem;letter-spacing:.4px;text-transform:uppercase}

/* --- Figures --- */
figure{margin:24px 0;text-align:center}
figure svg{max-width:100%;height:auto;border-radius:var(--radius);background:var(--surface);padding:14px;border:1px solid var(--border)}
figcaption{color:var(--muted);font-size:.9rem;margin-top:8px;font-style:italic}

/* --- Footer --- */
footer.site-footer{
  background:var(--secondary);color:#cbd5e1;
  padding:38px 0 22px;margin-top:60px;
  font-size:.94rem;
}
footer.site-footer a{color:#f1f5f9}
footer.site-footer a:hover{color:var(--accent)}
footer.site-footer .cols{display:grid;grid-template-columns:2fr 1fr 1fr;gap:30px;margin-bottom:24px}
footer.site-footer h3{color:#f8fafc;margin:0 0 8px;font-size:1rem}
footer.site-footer ul{list-style:none;padding:0;margin:0}
footer.site-footer ul li{margin:5px 0;padding-left:0}
footer.site-footer ul li::before{content:none}
footer.site-footer .disclaimer{border-top:1px solid #475569;padding-top:18px;font-size:.85rem;color:#94a3b8}

/* --- Utility --- */
.muted{color:var(--muted);font-size:.9rem}
.pill{display:inline-block;padding:3px 10px;border-radius:999px;background:var(--surface-alt);color:var(--secondary);font-size:.8rem;font-weight:600;margin-right:4px}
.grid-2{display:grid;grid-template-columns:1fr 1fr;gap:22px;margin:22px 0}

/* --- Responsive --- */
@media(max-width:980px){
  footer.site-footer .cols{grid-template-columns:1fr 1fr}
  .grid-2{grid-template-columns:1fr}
}
@media(max-width:700px){
  body{font-size:16px}
  .hero{padding:38px 0 42px}
  nav.toc ol{columns:1}
  h2{font-size:1.28rem;padding:8px 12px}
  .author-box{flex-direction:column;align-items:center;text-align:center}
  footer.site-footer .cols{grid-template-columns:1fr}
  .site-header .container{justify-content:center;text-align:center}
  nav.primary{justify-content:center}
}

/* a11y additions */
.skip-link{position:absolute;left:-9999px;top:0;background:var(--primary);color:#fff;padding:10px 16px;border-radius:4px;z-index:1000;text-decoration:none;font-weight:700}
.skip-link:focus{left:12px;top:12px}
a:focus-visible,button:focus-visible,summary:focus-visible{outline:3px solid var(--accent);outline-offset:2px}
@media (prefers-reduced-motion: reduce){*,*::before,*::after{transition-duration:.01ms !important;animation-duration:.01ms !important}}