:root{
  --primary:#dc2626;
  --secondary:#991b1b;
  --accent:#0891b2;
  --bg:#ffffff;
  --surface:#fef2f2;
  --surface-alt:#fee2e2;
  --text:#7f1d1d;
  --muted:#5f6e7d;
  --border:#fecaca;
  --row-alt:#fef2f2;
  --radius:10px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen,Ubuntu,Cantarell,sans-serif;
  background:var(--bg);
  color:var(--text);
  line-height:1.65;
  font-size:16px;
}
a{color:var(--secondary);text-decoration:underline;text-underline-offset:2px}
a:hover{color:var(--primary)}
img,svg{max-width:100%;height:auto}
.container{max-width:960px;margin:0 auto;padding:0 20px}

/* Header */
.site-header{
  position:sticky;top:0;z-index:50;
  background:linear-gradient(135deg,var(--primary) 0%,var(--secondary) 60%,var(--accent) 100%);
  color:#fff;
  box-shadow:0 2px 10px rgba(127,29,29,.18);
}
.site-header .container{display:flex;align-items:center;justify-content:space-between;gap:16px;padding:12px 20px;flex-wrap:wrap}
.brand{display:flex;align-items:center;gap:10px;color:#fff;text-decoration:none;font-weight:700;font-size:1.15rem;letter-spacing:.3px}
.brand img{width:36px;height:36px;background:#fff;border-radius:8px;padding:3px}
nav.primary ul{list-style:none;margin:0;padding:0;display:flex;flex-wrap:wrap;gap:6px 14px}
nav.primary a{color:#fff;text-decoration:none;font-weight:500;font-size:.95rem;padding:4px 6px;border-radius:6px}
nav.primary a:hover{background:rgba(255,255,255,.14)}

/* Hero */
.hero{
  background:linear-gradient(135deg,var(--surface) 0%,var(--surface-alt) 55%,#e0f2fe 100%);
  padding:56px 0 44px;
  border-bottom:1px solid var(--border);
}
.hero h1{margin:0 0 12px;font-size:2.05rem;line-height:1.2;color:var(--secondary);letter-spacing:-.01em}
.byline{margin:0 0 18px;color:var(--muted);font-size:.95rem}
.byline strong{color:var(--text)}
.intro p{font-size:1.08rem;margin:0 0 10px}
.cta-row{display:flex;flex-wrap:wrap;gap:10px;margin-top:22px}
.btn{
  display:inline-block;padding:10px 18px;border-radius:var(--radius);
  text-decoration:none;font-weight:600;
  background:var(--primary);color:#fff;border:2px solid var(--primary);
}
.btn:hover{background:var(--secondary);border-color:var(--secondary);color:#fff}
.btn.ghost{background:transparent;color:var(--secondary);border-color:var(--secondary)}
.btn.ghost:hover{background:var(--secondary);color:#fff}

/* TOC */
.toc{
  background:var(--surface);
  border:1px solid var(--border);
  border-left:4px solid var(--accent);
  border-radius:var(--radius);
  padding:18px 22px;
  margin:34px 0;
}
.toc strong{display:block;margin-bottom:8px;color:var(--secondary);letter-spacing:.02em;text-transform:uppercase;font-size:.85rem}
.toc ol{margin:0;padding-left:22px}
.toc li{margin:4px 0}
.toc a{color:var(--text);text-decoration:none}
.toc a:hover{color:var(--primary);text-decoration:underline}

/* Sections */
main.container{padding:40px 20px 60px}
main h2{
  margin-top:44px;
  padding-left:14px;
  border-left:5px solid var(--primary);
  color:var(--secondary);
  font-size:1.55rem;
  line-height:1.3;
}
main h3{color:var(--secondary);margin-top:26px;font-size:1.18rem}
main p,main li{font-size:1.02rem}
main ul{padding-left:22px;list-style:none}
main ul li{position:relative;padding-left:22px;margin:6px 0}
main ul li::before{content:"\27A4";position:absolute;left:0;color:var(--accent);font-weight:700}
main ol{padding-left:0;list-style:none;counter-reset:num}
main ol li{position:relative;padding-left:44px;margin:10px 0;counter-increment:num}
main ol li::before{
  content:counter(num);
  position:absolute;left:0;top:2px;
  width:30px;height:30px;border-radius:50%;
  background:linear-gradient(135deg,var(--primary),var(--accent));color:#fff;
  display:flex;align-items:center;justify-content:center;
  font-weight:700;font-size:.9rem;
}

/* Tables */
.table-wrap{overflow-x:auto;margin:22px 0;border:1px solid var(--border);border-radius:var(--radius)}
table{width:100%;border-collapse:collapse;font-size:.97rem;background:#fff}
thead th{
  background:linear-gradient(135deg,var(--primary),var(--secondary));
  color:#fff;text-align:left;padding:12px 14px;font-weight:600;
}
tbody td{padding:11px 14px;border-top:1px solid var(--border);vertical-align:top}
tbody tr:nth-child(even){background:var(--row-alt)}

/* FAQ */
details{
  background:var(--surface);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:14px 18px;
  margin:10px 0;
}
details summary{
  cursor:pointer;font-weight:600;color:var(--secondary);
  list-style:none;position:relative;padding-right:28px;
}
details summary::-webkit-details-marker{display:none}
details summary::after{
  content:"\25BC";
  position:absolute;right:0;top:50%;transform:translateY(-50%);
  color:var(--accent);transition:transform .2s ease;
  font-size:.85rem;
}
details[open] summary::after{transform:translateY(-50%) rotate(180deg)}
details p{margin:10px 0 0}

/* Callout / info */
.callout{
  background:linear-gradient(135deg,#fee2e2,#e0f2fe);
  border:1px solid var(--border);
  border-radius:var(--radius);
  padding:16px 20px;
  margin:22px 0;
}
.callout strong{color:var(--secondary)}

/* Author box */
.author-box{
  display:flex;gap:16px;align-items:flex-start;
  background:linear-gradient(135deg,var(--surface),#e0f2fe);
  border:1px solid var(--border);border-radius:var(--radius);
  padding:20px;margin:36px 0 0;
}
.author-box img{width:72px;height:72px;border-radius:50%;flex:none;background:#fff}
.author-box .who{margin:0 0 4px;font-size:1.05rem;color:var(--secondary);font-weight:700}
.author-box .role{margin:0 0 8px;color:var(--muted);font-size:.9rem}
.author-box p{margin:0;font-size:.97rem}

/* Figures */
figure{margin:24px 0;text-align:center}
figure svg{max-width:100%;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);padding:10px}
figcaption{font-size:.88rem;color:var(--muted);margin-top:6px}

/* Footer */
.site-footer{
  background:var(--surface);
  border-top:1px solid var(--border);
  padding:28px 0;margin-top:60px;font-size:.92rem;color:var(--muted);
}
.site-footer .container{display:flex;flex-wrap:wrap;gap:16px;justify-content:space-between;align-items:center}
.site-footer a{color:var(--secondary);text-decoration:none}
.site-footer a:hover{text-decoration:underline}
.foot-links{display:flex;flex-wrap:wrap;gap:10px 16px}

/* Responsive */
@media (max-width:980px){
  .hero h1{font-size:1.8rem}
  main h2{font-size:1.4rem}
}
@media (max-width:700px){
  .hero{padding:36px 0 28px}
  .hero h1{font-size:1.55rem}
  .site-header .container{flex-direction:column;align-items:flex-start}
  nav.primary ul{gap:4px 10px}
  main h2{font-size:1.3rem}
  .author-box{flex-direction:column}
  .author-box img{width:64px;height:64px}
}

/* 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}}