html,body{font-family:system-ui,-apple-system,Segoe UI,Roboto,Ubuntu,Cantarell,Helvetica Neue,Arial,"Apple Color Emoji","Segoe UI Emoji";margin:0}button{background:#111;color:#fff}button:hover{filter:brightness(1.1)}.container{max-width:720px;margin:0 auto;padding:16px}