:root {
  --bg: #fafaf9;
  --fg: #18181b;
  --muted: #71717a;
  --border: #e4e4e7;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --card: #ffffff;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 720px;
  margin: 0 auto;
  padding: 4rem 1.5rem;
}

.container-wide { max-width: 960px; }

header { margin-bottom: 3rem; }

nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.9rem;
  color: var(--muted);
}

nav a { color: var(--muted); text-decoration: none; }
nav a:hover { color: var(--fg); }

h1 {
  font-size: 2.5rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.75rem;
  line-height: 1.2;
}

h2 {
  font-size: 1.5rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-top: 2.5rem;
  margin-bottom: 1rem;
}

h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-top: 1.5rem;
  margin-bottom: 0.5rem;
}

p { margin-bottom: 1rem; }

.lead {
  font-size: 1.15rem;
  color: var(--muted);
  margin-bottom: 2rem;
}

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

.button {
  display: inline-block;
  padding: 0.75rem 1.25rem;
  background: var(--fg);
  color: var(--bg);
  border-radius: 0.5rem;
  font-weight: 500;
  font-size: 0.95rem;
  text-decoration: none;
  transition: opacity 0.15s;
  margin-right: 0.5rem;
}

.button:hover { opacity: 0.85; color: var(--bg); text-decoration: none; }

.button-secondary {
  background: transparent;
  color: var(--fg);
  border: 1px solid var(--border);
}

.button-secondary:hover { background: var(--card); color: var(--fg); }

.button-row { margin: 2rem 0; }

ul, ol { margin: 1rem 0 1rem 1.5rem; }
li { margin-bottom: 0.5rem; }

code {
  font-family: ui-monospace, "SF Mono", Menlo, monospace;
  font-size: 0.9em;
  background: var(--card);
  padding: 0.15rem 0.4rem;
  border-radius: 0.25rem;
  border: 1px solid var(--border);
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1.5rem;
  margin-bottom: 1rem;
  transition: border-color 0.15s;
}

.card:hover { border-color: var(--muted); }

.card h3 { margin-top: 0; }
.card p { color: var(--muted); margin-bottom: 0; }

.grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
  margin: 2rem 0;
}

@media (min-width: 640px) {
  .grid-2 { grid-template-columns: repeat(2, 1fr); }
}

footer {
  margin-top: 4rem;
  padding-top: 2rem;
  border-top: 1px solid var(--border);
  font-size: 0.875rem;
  color: var(--muted);
  display: flex;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
}

footer a { color: var(--muted); }
footer a:hover { color: var(--fg); }

.muted { color: var(--muted); }
.small { font-size: 0.875rem; }

hr {
  border: 0;
  border-top: 1px solid var(--border);
  margin: 2rem 0;
}