:root {
  --action: #ff8a80;
  --concept: #b39ddb;
  --detail: #90caf9;
  --relations: #a5d6a7;
  --ink: #2b2b3a;
  --muted: #6b6b7d;
  --card: #ffffffcc;
}
* { box-sizing: border-box; }
html, body {
  margin: 0;
  padding: 0;
  min-height: 100%;
}
body {
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--ink);
  background:
    radial-gradient(1200px 800px at 10% 0%, var(--bg-from, #ffe6e6) 0%, transparent 60%),
    radial-gradient(1200px 800px at 100% 100%, var(--bg-to, #e6f0ff) 0%, transparent 60%),
    linear-gradient(180deg, #fafaff 0%, #f3f4ff 100%);
  background-attachment: fixed;
  transition: background 600ms ease;
  line-height: 1.5;
}
main {
  max-width: 720px;
  margin: 0 auto;
  padding: 24px 20px 80px;
}

/* nav */
nav.topnav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 8px 0 20px;
  font-size: 14px;
}
nav.topnav .brand {
  font-weight: 800;
  letter-spacing: -0.01em;
  font-size: 16px;
  background: linear-gradient(90deg, var(--action), var(--concept), var(--detail), var(--relations));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  text-decoration: none;
}
nav.topnav .links {
  display: flex;
  gap: 6px;
}
nav.topnav a.link {
  color: var(--muted);
  text-decoration: none;
  padding: 6px 12px;
  border-radius: 999px;
  transition: background 120ms ease, color 120ms ease;
}
nav.topnav a.link:hover { background: #ffffff80; color: var(--ink); }
nav.topnav a.link.active {
  background: var(--card);
  color: var(--ink);
  box-shadow: 0 2px 8px rgba(60,60,100,0.06);
}

/* heading */
header h1 {
  font-size: 40px;
  margin: 0 0 4px;
  letter-spacing: -0.02em;
  background: linear-gradient(90deg, var(--action), var(--concept), var(--detail), var(--relations));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  font-weight: 800;
}
header p.strap {
  margin: 0 0 28px;
  color: var(--muted);
  font-size: 15px;
}

/* shared chip */
.chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 12px;
  border-radius: 999px;
  font-weight: 600;
  font-size: 14px;
  color: #2b2b3a;
}
.chip .dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex: 0 0 10px;
}

/* cards */
.surface {
  background: var(--card);
  backdrop-filter: blur(6px);
  border-radius: 22px;
  padding: 22px 24px;
  box-shadow: 0 10px 30px rgba(60, 60, 100, 0.10);
  border: 1px solid #ffffffaa;
}
.surface + .surface { margin-top: 16px; }

/* footer legend */
footer.legend-row {
  margin-top: 28px;
  color: var(--muted);
  font-size: 13px;
  display: flex;
  flex-wrap: wrap;
  gap: 12px 18px;
  justify-content: center;
}
footer.legend-row .legend {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
footer.legend-row .legend .dot {
  width: 9px; height: 9px; border-radius: 50%;
}

@media (max-width: 520px) {
  main { padding: 16px 14px 60px; }
  header h1 { font-size: 32px; }
  nav.topnav { font-size: 13px; }
}