:root {
  color-scheme: light dark;
  --bg: #f5f3ff;
  --surface: #ffffff;
  --text: #17132b;
  --muted: #68627d;
  --line: #ded9f2;
  --brand: #6847ff;
  --brand-soft: #ebe7ff;
  --shadow: 0 16px 44px rgba(45, 30, 105, 0.09);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans JP", sans-serif;
  line-height: 1.75;
}
a { color: var(--brand); }
.shell { width: min(920px, calc(100% - 32px)); margin: 0 auto; }
header { padding: 28px 0 18px; }
nav { display: flex; flex-wrap: wrap; gap: 10px 18px; align-items: center; }
.brand { margin-right: auto; color: var(--text); font-weight: 800; text-decoration: none; }
.brand-mark { color: var(--brand); }
nav a:not(.brand) { color: var(--muted); font-size: .92rem; text-decoration: none; }
main { padding: 22px 0 64px; }
.hero, article {
  border: 1px solid var(--line);
  border-radius: 22px;
  background: var(--surface);
  box-shadow: var(--shadow);
}
.hero { padding: clamp(28px, 6vw, 58px); }
.eyebrow { color: var(--brand); font-size: .8rem; font-weight: 800; letter-spacing: .12em; }
h1 { margin: 8px 0 12px; font-size: clamp(2rem, 6vw, 3.6rem); line-height: 1.2; }
h2 { margin-top: 2.2em; line-height: 1.35; }
h3 { margin-top: 1.8em; line-height: 1.4; }
p, li { color: var(--muted); }
.lead { max-width: 660px; font-size: 1.08rem; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 24px; }
.button { display: inline-block; padding: 11px 16px; border-radius: 12px; background: var(--brand); color: white; font-weight: 700; text-decoration: none; }
.button.secondary { background: var(--brand-soft); color: var(--brand); }
.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; margin-top: 18px; }
.card { padding: 20px; border: 1px solid var(--line); border-radius: 16px; background: var(--surface); }
.card h2 { margin: 0 0 6px; font-size: 1.05rem; }
article { margin-top: 18px; padding: clamp(24px, 5vw, 52px); }
.meta, .note { padding: 14px 16px; border-radius: 12px; background: var(--brand-soft); color: var(--muted); }
.lang { margin-top: 52px; padding-top: 38px; border-top: 1px solid var(--line); }
footer { padding: 24px 0 42px; color: var(--muted); font-size: .88rem; text-align: center; }
@media (max-width: 680px) { .grid { grid-template-columns: 1fr; } }
@media (prefers-color-scheme: dark) {
  :root { --bg: #100d1d; --surface: #191529; --text: #f6f2ff; --muted: #bbb3ce; --line: #352e4b; --brand-soft: #292047; --shadow: none; }
}