:root{font-family:system-ui,-apple-system,Segoe UI,Roboto,Hiragino Kaku Gothic ProN,Noto Sans JP,sans-serif;line-height:1.6;color:#1f2937}*{box-sizing:border-box}body{margin:0;background:#f8fafc}main{max-width:960px;margin:0 auto;padding:2rem 1rem}