:root {
  --bg: #06121d;
  --bg-soft: #0d2233;
  --text: #e6f1ff;
  --muted: #9bb4c9;
  --line: #2b4f6a;
  --accent: #16c5a3;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "IBM Plex Sans", "Segoe UI", sans-serif;
  background: radial-gradient(circle at top left, #15324a 0%, var(--bg) 60%);
  color: var(--text);
}

.hero {
  padding: 64px 20px 40px;
  border-bottom: 1px solid var(--line);
}

.hero-content {
  max-width: 980px;
  margin: 0 auto;
}

.eyebrow {
  color: var(--accent);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.85rem;
}

h1 { margin: 6px 0 10px; font-size: clamp(2rem, 5vw, 3.2rem); }
.lead { color: var(--muted); max-width: 720px; }

.cta-row { margin-top: 20px; display: flex; gap: 10px; flex-wrap: wrap; }

.btn {
  display: inline-block;
  padding: 10px 14px;
  border-radius: 10px;
  text-decoration: none;
  border: 1px solid var(--line);
}

.btn.primary { background: var(--accent); color: #05201b; border-color: transparent; font-weight: 700; }
.btn.secondary { color: var(--text); }

main { max-width: 980px; margin: 0 auto; padding: 20px; }
.section { margin: 18px 0; padding: 18px; background: rgba(13, 34, 51, 0.65); border: 1px solid var(--line); border-radius: 14px; }
.section.alt { background: rgba(9, 26, 40, 0.8); }

.grid.three { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 10px; }
.card { border: 1px solid var(--line); border-radius: 12px; padding: 12px; background: rgba(8, 20, 30, 0.9); }
.card h3 { margin-top: 0; }

.diagram {
  white-space: pre-wrap;
  background: #03101a;
  border: 1px dashed var(--line);
  border-radius: 10px;
  padding: 12px;
}

footer { text-align: center; padding: 18px; color: var(--muted); }

@media (max-width: 900px) {
  .grid.three { grid-template-columns: 1fr; }
}