body{font-family:Arial,sans-serif;background-color:#f0f0f0;text-align:center;margin:0;padding:0}h1{color:#333}.calculator{background-color:#fff;max-width:400px;margin:20px auto;padding:20px;border-radius:5px;box-shadow:0 0 10px rgb(0 0 0 / .2)}label{display:block;margin-bottom:10px}input[type="number"]{width:100%;padding:10px;margin-bottom:10px;border:1px solid #ccc;border-radius:3px}button{background-color:#007bff;color:#fff;border:none;padding:10px 20px;border-radius:3px;cursor:pointer}button:hover{background-color:#0056b3}#result{font-size:18px;margin-top:20px}