*{margin:0;padding:0;box-sizing:border-box}body{line-height:1.5}:root{--primary-color:#3498db;--text-color:#333}body{font-family:sans-serif;color:var(--text-color);background-color:#f4f4f4;padding:20px}header h1{color:var(--primary-color);margin-bottom:25px}#action-button{background-color:var(--primary-color);color:#fff;border:none;padding:10px 20px;cursor:pointer;border-radius:5px;transition:background-color .3s ease}.message{margin-top:15px;font-style:italic;color:green}