body{
            background: #111;
            display: flex;
            justify-content: center;
            align-items: center;
            height: 100vh;
            font-family: tahoma;
        }
        .calculator{
            background: #222;
            padding: 20px;
            border-radius: 12px;
            box-shadow: 0 0 20px black;
        }
        #display{
            width: 100%;
            height: 55px;
            font-size: 22px;
            margin-bottom: 10px;
            text-align: right;
            padding: 5px;
        }
        button{
            width: 65px;
            height: 55px;
            margin: 4px;
            font-size: 18px;
            border: none;
            border-radius: 8px;
            cursor: pointer;
        }
        button:hover{
            background: #444;
            color: white;
        }
        .row{
            text-align: center;
        }