body{
    font-family: Arial;
    background:#222;
    color:white;
    display:flex;
    justify-content:center;
    align-items:center;
    height:100vh;
}

.container{
    text-align:center;
    background:#333;
    padding:30px;
    border-radius:10px;
}

#display{
    font-size:50px;
    margin:20px;
}

button{
    padding:10px 20px;
    margin:5px;
    border:none;
    border-radius:5px;
    cursor:pointer;
    font-size:16px;
}

button:hover{
    background:orange;
}

ul{
    margin-top:20px;
    text-align:left;
}