main.css

body{
    background-color: rgb(214, 214, 214);
}

.container{
    width: 250px;
    height: 400px;
    margin: 80px auto;
    border-radius: 10px;
    background-color: rgb(214, 214, 214);
    box-shadow: 5px 5px 10px rgb(137, 127, 127), -5px -5px 10px white;
}

.cal-box{
    width: 200px;
    margin: 20px auto;
}

#display{
    border: none;
    outline: none;
    color: black;
    text-align: right;
    font-weight: 600;
    padding: 15px;
    margin: 30px 0 20px 0;
    background: transparent;
    box-shadow: inset 5px 5px 10px #babecc, inset -5px -5px 10px white;
}

.button{
    margin: 15px 0 0 5px;
    width: 42px;
    height: 42px;
    border: none;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    border-radius: 8px;
    background: rgb(214, 214, 214);
    box-shadow:  5px 5px 10px #babecc, -5px -5px 10px #faf4f4;
    display: inline-block;
}

.button:active{
    box-shadow: inset 1px 1px 2px #babecc, inset -1px -1px 2px white;
}

.clearButton{
    background: red;
    color: white;
}

.mathbutton{
    background: black;
    color: white;
}