:root {
  --bg: #0a0e1a;
  --bg-card: #121829;
  --bg-elev: #1a2238;
  --border: #2a3454;
  --text: #e6ecff;
  --text-dim: #8a93b3;
  --accent: #7c5cff;
  --accent2: #00d4ff;
  --accent3: #ff5c8a;
  --success: #2dd4bf;
  --warn: #f59e0b;
  --danger: #ef4444;
  --mono: 'JetBrains Mono', ui-monospace, 'Cascadia Mono', Consolas, monospace;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; background: var(--bg); color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, system-ui, sans-serif;
  line-height: 1.55;
}

a { color: var(--accent2); text-decoration: none; }
a:hover { color: var(--accent); }

.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(10,14,26,0.85);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 1.5rem;
  display: flex; align-items: center; gap: 1.5rem; flex-wrap: wrap;
}
.nav .logo {
  font-weight: 700; letter-spacing: 0.5px;
  background: linear-gradient(90deg, var(--accent), var(--accent2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
  font-size: 1.05rem;
}
.nav a.navlink {
  color: var(--text-dim); font-size: 0.88rem; font-weight: 500;
  padding: 0.3rem 0.6rem; border-radius: 6px;
  transition: all 0.15s;
}
.nav a.navlink:hover { color: var(--text); background: var(--bg-elev); }
.nav a.navlink.active { color: var(--text); background: var(--bg-elev); }

main { max-width: 1200px; margin: 0 auto; padding: 2rem 1.5rem 4rem; }

.hero {
  text-align: center; padding: 3rem 1rem 2rem;
}
.hero h1 {
  font-size: clamp(2rem, 5vw, 3.4rem); margin: 0 0 0.8rem;
  background: linear-gradient(135deg, var(--accent), var(--accent2) 60%, var(--accent3));
  -webkit-background-clip: text; background-clip: text; color: transparent;
  font-weight: 800; letter-spacing: -0.02em;
}
.hero p { color: var(--text-dim); font-size: 1.1rem; max-width: 720px; margin: 0 auto; }
.hero .tagline { font-family: var(--mono); color: var(--accent2); font-size: 0.85rem;
  text-transform: uppercase; letter-spacing: 0.2em; margin-bottom: 1rem; }

.grid { display: grid; gap: 1rem; }
.grid.cards { grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.25rem;
  transition: all 0.2s;
  position: relative; overflow: hidden;
}
.card:hover { border-color: var(--accent); transform: translateY(-2px); }
.card .num {
  position: absolute; top: 0.6rem; right: 0.9rem;
  font-family: var(--mono); font-size: 0.7rem; color: var(--text-dim);
}
.card h3 { margin: 0.2rem 0 0.5rem; font-size: 1.1rem; }
.card p { margin: 0; color: var(--text-dim); font-size: 0.92rem; }
.card .tag {
  display: inline-block; font-family: var(--mono); font-size: 0.7rem;
  padding: 0.15rem 0.5rem; border-radius: 4px;
  background: var(--bg-elev); color: var(--accent2);
  margin-top: 0.8rem;
}

h2 {
  font-size: 1.6rem; margin-top: 2.5rem; margin-bottom: 0.8rem;
  display: flex; align-items: center; gap: 0.6rem;
}
h2::before {
  content: ''; width: 4px; height: 1.3rem;
  background: linear-gradient(180deg, var(--accent), var(--accent2));
  border-radius: 2px;
}
h3 { font-size: 1.1rem; margin: 1.5rem 0 0.6rem; }

p { color: var(--text); }
.muted { color: var(--text-dim); }
code, .mono { font-family: var(--mono); }
code {
  background: var(--bg-elev); padding: 0.1rem 0.4rem; border-radius: 4px;
  font-size: 0.88em; color: var(--accent2);
}

.demo {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 1.25rem;
  margin: 1.25rem 0;
}
.demo-title {
  font-size: 0.78rem; font-family: var(--mono);
  color: var(--accent); text-transform: uppercase; letter-spacing: 0.15em;
  margin-bottom: 0.8rem;
}

.controls {
  display: flex; flex-wrap: wrap; gap: 0.6rem 1.2rem;
  align-items: center;
  padding: 0.75rem; margin: 0.75rem 0;
  background: var(--bg-elev); border-radius: 10px;
}
.controls label {
  display: flex; flex-direction: column; gap: 0.2rem;
  font-size: 0.78rem; color: var(--text-dim); font-family: var(--mono);
  text-transform: uppercase; letter-spacing: 0.05em;
}
.controls input[type=range] {
  width: 140px; accent-color: var(--accent);
}
.controls select, .controls input[type=number] {
  background: var(--bg); color: var(--text);
  border: 1px solid var(--border); border-radius: 6px;
  padding: 0.35rem 0.5rem; font-family: var(--mono); font-size: 0.85rem;
}
.controls .val { color: var(--accent2); font-family: var(--mono); font-size: 0.9rem; }

.btn {
  background: var(--accent); color: white;
  border: none; border-radius: 8px;
  padding: 0.5rem 1rem; font-weight: 600; font-size: 0.88rem;
  cursor: pointer; transition: all 0.15s;
  font-family: inherit;
}
.btn:hover { background: #6a4af0; transform: translateY(-1px); }
.btn:active { transform: translateY(0); }
.btn.ghost { background: transparent; border: 1px solid var(--border); color: var(--text); }
.btn.ghost:hover { border-color: var(--accent); background: var(--bg-elev); }
.btn.alt { background: var(--accent2); color: #001020; }
.btn.alt:hover { background: #00b4dd; }
.btn.danger { background: var(--danger); }

.canvas-wrap {
  background: #050811; border: 1px solid var(--border);
  border-radius: 10px; overflow: hidden;
  display: flex; justify-content: center; align-items: center;
  margin: 0.75rem 0;
}
canvas { display: block; max-width: 100%; }

.split { display: grid; gap: 1rem; grid-template-columns: 1fr 1fr; }
@media (max-width: 760px) { .split { grid-template-columns: 1fr; } }

.stats { display: grid; gap: 0.5rem; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr)); }
.stat {
  background: var(--bg-elev); border-radius: 8px;
  padding: 0.6rem 0.8rem; border: 1px solid var(--border);
}
.stat .lbl {
  display: block; font-size: 0.7rem; color: var(--text-dim);
  font-family: var(--mono); text-transform: uppercase; letter-spacing: 0.1em;
}
.stat .v {
  display: block; font-size: 1.2rem; font-weight: 700;
  font-family: var(--mono); color: var(--accent2); margin-top: 0.2rem;
}

.legend { display: flex; flex-wrap: wrap; gap: 0.75rem; font-size: 0.8rem; color: var(--text-dim); }
.legend .sw { display: inline-block; width: 12px; height: 12px; border-radius: 3px; margin-right: 0.4rem; vertical-align: middle; }

.math {
  background: var(--bg-elev); border-left: 3px solid var(--accent);
  padding: 0.7rem 1rem; border-radius: 0 8px 8px 0;
  font-family: var(--mono); font-size: 0.95em;
  margin: 1rem 0; overflow-x: auto;
}

.note {
  background: rgba(124, 92, 255, 0.08);
  border: 1px solid rgba(124, 92, 255, 0.3);
  border-radius: 10px; padding: 0.8rem 1rem; margin: 1rem 0;
  color: var(--text);
}
.note strong { color: var(--accent); }

.callout {
  border-left: 3px solid var(--accent2);
  padding: 0.6rem 1rem; margin: 1rem 0;
  background: rgba(0, 212, 255, 0.05); border-radius: 0 8px 8px 0;
  font-size: 0.95em;
}

footer {
  text-align: center; padding: 2rem 1rem;
  color: var(--text-dim); font-size: 0.85rem; border-top: 1px solid var(--border);
  margin-top: 4rem;
}

/* Toggle button group */
.toggle-group { display: inline-flex; background: var(--bg); border: 1px solid var(--border); border-radius: 8px; padding: 2px; }
.toggle-group button {
  background: transparent; border: none; color: var(--text-dim);
  padding: 0.35rem 0.75rem; cursor: pointer;
  font-size: 0.82rem; font-weight: 600; border-radius: 6px;
}
.toggle-group button.on { background: var(--accent); color: white; }

table.kv { width: 100%; border-collapse: collapse; font-family: var(--mono); font-size: 0.85rem; }
table.kv td { padding: 0.3rem 0.6rem; border-bottom: 1px solid var(--border); }
table.kv td:first-child { color: var(--text-dim); }

ul.ck { list-style: none; padding-left: 0.5rem; }
ul.ck li { padding-left: 1.2rem; position: relative; margin-bottom: 0.3rem; }
ul.ck li::before { content: '▸'; color: var(--accent); position: absolute; left: 0; }