*{
    margin: 0;
    padding: 0;
}

#container{
    border: 4mm ridge rgba(29, 53, 87, .6);
    width: 700px;
    height: 700px;
    margin: 20px auto;
    padding: 17px;
}

#calculator{
    border: 4px solid red;
    width: 90%;
    margin: 10px auto;
    border-radius: 5px;
    padding: 15px;
}

button{
    font-size: 24px;
    display: block;
    height: 100%;
    width: 100%;
    border-radius: 10px;
}

button:focus{
    outline: none;
}

h1{
    text-align: center;
    font-family:'Courier New', Courier, monospace;
    font-size: 50px;
}

#screen{
    font-size: 42px;
    margin: 5px auto;
    display: block;
}

table{
    margin: 10px auto;
}

td{
    height: 70px;
    width: 90px;
    border-radius: 10px;
    box-shadow: 0px 2px 3px #ccc;
    transition: 100ms;
}

button:hover{
    cursor:pointer;
}

td:active{
    transform: scale(0.8);
}