:root {
  color-scheme: light;
  --background: 0 0% 100%;
  --foreground: 230 100% 27%;
  --muted: 220 14% 96%;
  --muted-foreground: 215 16% 37%;
  --primary: 230 100% 27%;
  --primary-foreground: 0 0% 100%;
  --accent: 193 65% 71%;
  --border: 220 13% 85%;
}
* { box-sizing: border-box; }
body { margin: 0; font-family: Arial, sans-serif; color: hsl(var(--foreground)); background: hsl(var(--background)); line-height: 1.65; }
a { color: hsl(var(--primary)); text-underline-offset: .2em; }
a:focus-visible { outline: 3px solid hsl(var(--accent)); outline-offset: 4px; }
header { border-bottom: 1px solid hsl(var(--border)); }
.header-inner, main, .footer-inner { max-width: 1100px; margin: auto; padding: 24px; }
.header-inner { display: flex; align-items: center; justify-content: space-between; gap: 20px; }
.brand { display: flex; align-items: center; gap: 12px; text-decoration: none; font-weight: bold; }
.brand img { width: 48px; height: 48px; }
nav { display: flex; flex-wrap: wrap; gap: 20px; }
h1 { font-size: 40px; line-height: 1.15; margin: 28px 0 20px; }
h2 { font-size: 24px; line-height: 1.3; margin: 0 0 12px; }
.intro { max-width: 760px; font-size: 20px; color: hsl(var(--muted-foreground)); }
.contents { display: flex; flex-wrap: wrap; gap: 12px 24px; padding: 24px 0; border-block: 1px solid hsl(var(--border)); margin: 32px 0; }
.features { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 48px; }
section { padding: 28px 0; border-bottom: 1px solid hsl(var(--border)); scroll-margin-top: 24px; }
section p, section li { color: hsl(var(--muted-foreground)); }
ul { padding-left: 22px; }
footer { background: hsl(var(--muted)); margin-top: 40px; }
.footer-inner { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 20px; }
@media (max-width: 640px) {
  .header-inner { align-items: flex-start; flex-direction: column; }
  h1 { font-size: 32px; }
  .features { grid-template-columns: 1fr; }
}