:root { color-scheme: light; font-family: "Noto Sans JP", "Yu Gothic", sans-serif; background: #f5f7fb; color: #182033; }
* { box-sizing: border-box; }
body { min-height: 100vh; margin: 0; display: grid; place-items: center; padding: 24px; }
main { width: min(520px, 100%); padding: 36px 28px; text-align: center; background: #fff; border: 1px solid #e4e9f2; border-radius: 24px; box-shadow: 0 18px 50px rgba(24, 32, 51, .10); }
.mark { width: 58px; height: 58px; margin: 0 auto 18px; display: grid; place-items: center; color: #fff; background: #111827; border-radius: 18px; font-size: 21px; font-weight: 800; }
h1 { margin: 0 0 12px; font-size: clamp(22px, 6vw, 30px); line-height: 1.4; }
p { margin: 0 0 24px; color: #556176; line-height: 1.8; }
a { display: inline-block; padding: 13px 22px; color: #fff; background: #111827; border-radius: 999px; font-weight: 700; text-decoration: none; }