:root{
  --font: "Segoe UI", system-ui, -apple-system, Roboto, Arial, "Apple Color Emoji","Segoe UI Emoji";

  --radius: 16px;
  --radius-sm: 12px;

  --accent: #2563eb;
  --accent-2: #0ea5e9;

  /* Light (default) */
  --bg: #f6f7fb;
  --surface: #ffffff;
  --surface-2: rgba(255,255,255,.72);
  --text: #0b1220;
  --muted: #4b5563;
  --line: rgba(15, 23, 42, .12);

  --shadow: 0 10px 30px rgba(2, 6, 23, .10);
  --shadow-soft: 0 6px 18px rgba(2, 6, 23, .08);
}

/* Dark = second option */
html[data-theme="dark"]{
  --bg: #0b0f14;
  --surface: #0f1621;
  --surface-2: rgba(15, 22, 33, .70);
  --text: #e9eef5;
  --muted: #a7b3c3;
  --line: rgba(255,255,255,.10);

  --shadow: 0 18px 60px rgba(0,0,0,.35);
  --shadow-soft: 0 12px 28px rgba(0,0,0,.30);
}

*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  font-family:var(--font);
  color:var(--text);
  line-height:1.55;
  background:
    radial-gradient(1200px 700px at 15% 10%, rgba(37,99,235,.12), transparent 55%),
    radial-gradient(900px 600px at 80% 20%, rgba(14,165,233,.10), transparent 50%),
    var(--bg);
}
a{color:inherit; text-decoration:none}
.container{max-width:1120px; margin:0 auto; padding:0 18px}

/* Acrylic header */
.site-header, .top{
  position:sticky; top:0; z-index:10;
  background: var(--surface-2);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
}

/* Header actions */
.header-actions{display:flex; align-items:center; gap:10px}

/* Brand */
.brand{display:flex; align-items:center; gap:10px}
.brand-name,.name{font-weight:700; letter-spacing:.2px}
.brand-mark,.mark{
  width:18px; height:18px; border-radius:6px;
  background: linear-gradient(135deg, rgba(37,99,235,.95), rgba(14,165,233,.80));
  box-shadow: 0 0 0 1px rgba(0,0,0,.10) inset;
}
html[data-theme="dark"] .brand-mark,
html[data-theme="dark"] .mark{
  box-shadow: 0 0 0 1px rgba(255,255,255,.10) inset;
}

/* Nav */
.nav{display:flex; gap:16px; align-items:center}
.nav a{
  color:var(--muted);
  font-size:14px;
  padding:8px 10px;
  border-radius:10px;
}
.nav a:hover{background:rgba(37,99,235,.08); color:var(--text)}

/* Fluent buttons */
.btn{
  display:inline-flex; align-items:center; justify-content:center; gap:10px;
  padding:10px 14px;
  border-radius: var(--radius-sm);
  border:1px solid var(--line);
  background: transparent;
  font-weight:600;
  font-size:14px;
  cursor:pointer;
}
.btn-primary{
  background: var(--accent);
  border-color: rgba(37,99,235,.45);
  color:#fff;
  box-shadow: 0 10px 22px rgba(37,99,235,.22);
}
.btn-primary:hover{filter:brightness(1.03)}
.btn-ghost:hover{background: rgba(37,99,235,.08)}
.btn.small{padding:9px 12px; font-size:13px}

/* Inputs */
input,select{
  width:100%;
  padding:12px 12px;
  border-radius: var(--radius-sm);
  border:1px solid var(--line);
  background: rgba(255,255,255,.70);
  color: var(--text);
  outline:none;
}
html[data-theme="dark"] input,
html[data-theme="dark"] select{
  background: rgba(15,22,33,.65);
}
input:focus,select:focus{
  border-color: rgba(37,99,235,.55);
  box-shadow: 0 0 0 4px rgba(37,99,235,.16);
}

/* Theme toggle dot */
.theme-dot{
  width:10px; height:10px; border-radius:999px;
  background: radial-gradient(circle at 30% 30%, #fff, var(--accent));
  box-shadow: 0 0 0 1px rgba(0,0,0,.10) inset;
}
html[data-theme="dark"] .theme-dot{
  box-shadow: 0 0 0 1px rgba(255,255,255,.10) inset;
}
.theme-label{color:var(--muted)}

.row{display:flex; align-items:center; justify-content:space-between; gap:14px; padding:14px 0; flex-wrap:wrap}

.layout{
  display:grid;
  grid-template-columns: 280px 1fr;
  gap:14px;
  padding:24px 0 44px;
}
.side{
  border:1px solid var(--line);
  background: var(--surface);
  border-radius: var(--radius);
  padding:16px;
  height: fit-content;
  position: sticky;
  top: 78px;
  box-shadow: var(--shadow-soft);
}
.side h2{margin:0 0 10px; font-size:18px; color: rgba(37,99,235,.95)}
.item{
  display:block;
  padding:10px 10px;
  border-radius:12px;
  color:var(--muted);
  border:1px solid transparent;
}
.item:hover{background:rgba(37,99,235,.08); color:var(--text)}
.item.active{border-color: rgba(37,99,235,.25); background: rgba(37,99,235,.08); color:var(--text)}

.content{padding:6px 0}
.eyebrow{color: rgba(37,99,235,.95); font-weight:800; letter-spacing:.12em; text-transform:uppercase; font-size:12px}
h1{margin:.2rem 0 .5rem; font-size:34px; line-height:1.15}
.lead{color:var(--muted); max-width:85ch}

.card{
  border:1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  padding:16px;
  margin-top:12px;
  box-shadow: var(--shadow-soft);
}
.card h3{margin:0 0 8px; font-size:16px}
.card ul, .card ol{margin:0; padding-left:18px; color:var(--muted)}
.card li{margin:8px 0}
.card strong{color: rgba(37,99,235,.95)}

.callout{
  margin-top:14px;
  border:1px solid rgba(37,99,235,.22);
  border-radius: var(--radius);
  background: rgba(37,99,235,.06);
  padding:16px;
}
.callout h3{margin:0 0 6px}
.callout p{margin:0 0 12px; color:var(--muted)}

.foot{border-top:1px solid var(--line); padding:16px 0; color:var(--muted); background: rgba(255,255,255,.40)}
html[data-theme="dark"] .foot{background: rgba(0,0,0,.12)}
.links{display:flex; gap:12px; flex-wrap:wrap}
.links a:hover{color:var(--text)}

@media (max-width: 920px){
  .layout{grid-template-columns:1fr}
  .side{position:relative; top:auto}
  .nav{display:none}
}