/* System font stack for Apple-like typography */
:root{
  --bg: #f5f5f7;
  --card: #ffffff;
  --text: #1d1d1f;
  --muted: #6e6e73;
  --border: #e5e5ea;
  --link: #007aff; /* iOS blue */
  --radius: 18px;
  --shadow: 0 8px 24px rgba(0,0,0,0.06);
  --container: 880px;
}

*{ box-sizing: border-box; }
html,body{ margin:0; padding:0; }
body{
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.container{
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 20px;
}

.site-header{
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(245,245,247,0.8);
  backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid var(--border);
}

.site-header .container{
  display:flex;
  align-items:center;
  justify-content:space-between;
  padding: 14px 20px;
}

.brand{
  font-weight: 700;
  letter-spacing: -0.01em;
  text-decoration: none;
  color: var(--text);
  font-size: 18px;
}

.nav .nav-link{
  display:inline-block;
  margin-left: 16px;
  padding: 8px 10px;
  border-radius: 10px;
  color: var(--text);
  text-decoration: none;
}
.nav .nav-link:hover{ background: rgba(0,0,0,0.04); }
.nav .nav-link.active{ color: var(--link); }

main.container{
  padding: 28px 20px 64px;
}

.card{
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px 22px;
  margin-bottom: 20px;
}

.title{
  margin: 0 0 8px;
  font-size: 28px;
  letter-spacing: -0.01em;
  font-weight: 700;
}

h2{
  font-size: 22px;
  margin: 12px 0 8px;
}
h3{
  font-size: 18px;
  margin: 14px 0 6px;
}
h4{
  font-size: 16px;
  color: var(--muted);
  margin: 10px 0 6px;
}

p{ margin: 10px 0; }
ul{ margin: 8px 0 12px 18px; }
li + li{ margin-top: 4px; }

.prose p:last-child{ margin-bottom: 0; }

.site-footer{
  border-top: 1px solid var(--border);
  background: var(--bg);
}
.site-footer .container{
  padding: 18px 20px;
  color: var(--muted);
  font-size: 14px;
}

/* Dark mode (honors user preference) */
@media (prefers-color-scheme: dark){
  :root{
    --bg: #000000;
    --card: #1c1c1e;
    --text: #f5f5f7;
    --muted: #a1a1a6;
    --border: #2c2c2e;
    --shadow: 0 8px 24px rgba(0,0,0,0.4);
  }
  .nav .nav-link:hover{ background: rgba(255,255,255,0.06); }
}