:root {
  --bg: #fafafa;
  --surface: #ffffff;
  --border: rgba(0, 0, 0, 0.08);
  --text: #111111;
  --text-dim: #52525b;
  --text-dimmer: #a1a1aa;
  --accent: #7c3aed;
  --accent-dim: rgba(124, 58, 237, 0.08);
  --sans: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --mono: ui-monospace, "Cascadia Code", monospace;
  --radius: 14px;
  --max: 720px;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

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

header {
  border-bottom: 0.5px solid var(--border);
  padding: 18px 24px;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  position: sticky;
  top: 0;
  z-index: 10;
  box-shadow: var(--shadow-sm);
}

.header-inner {
  max-width: 960px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.logo {
  font-weight: 800;
  letter-spacing: 0.18em;
  font-size: 14px;
  color: var(--text);
  text-decoration: none;
}

.logo:hover { text-decoration: none; opacity: 0.85; }

.badge {
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--accent);
  border: 1px solid rgba(124, 58, 237, 0.25);
  background: var(--accent-dim);
  padding: 4px 8px;
  border-radius: 6px;
}

nav {
  display: flex;
  gap: 18px;
  flex-wrap: wrap;
}

nav a {
  color: var(--text-dim);
  font-size: 13px;
  text-decoration: none;
}

nav a:hover { color: var(--text); text-decoration: none; }
nav a.active { color: var(--accent); }

main {
  max-width: var(--max);
  margin: 0 auto;
  padding: 48px 24px 80px;
}

h1 {
  font-size: clamp(28px, 5vw, 38px);
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 10px;
  color: var(--text);
}

.meta {
  color: var(--text-dimmer);
  font-size: 13px;
  margin-bottom: 32px;
}

.card {
  background: var(--surface);
  border: 0.5px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 24px;
  margin-bottom: 20px;
  box-shadow: var(--shadow-sm);
}

h2 {
  font-size: 18px;
  margin-bottom: 12px;
  color: var(--text);
}

h3 {
  font-size: 15px;
  margin: 18px 0 8px;
  color: var(--text);
}

p, li {
  color: var(--text-dim);
  margin-bottom: 10px;
}

ul, ol {
  padding-left: 20px;
  margin-bottom: 12px;
}

li { margin-bottom: 6px; }

.note {
  background: var(--accent-dim);
  border: 0.5px solid rgba(124, 58, 237, 0.2);
  border-radius: 10px;
  padding: 14px 16px;
  font-size: 14px;
  color: var(--text-dim);
  margin: 24px 0;
}

.note strong { color: var(--accent); }

footer {
  border-top: 0.5px solid var(--border);
  padding: 28px 24px 40px;
  text-align: center;
  color: var(--text-dimmer);
  font-size: 12px;
  background: var(--surface);
}

footer a { color: var(--text-dim); margin: 0 8px; }

@media (max-width: 640px) {
  header { padding: 14px 16px; }
  main { padding: 32px 16px 60px; }
  .card { padding: 22px 18px; }
}