body{
    background-color: gray;
    font-size: 26px;
    font-weight: bold;
    font-family: 'Times New Roman', Times, serif;
}
.main-body{
    margin-top:100px;
    height:400px;
    width:300px;
    }

.calc{
     background-color: rgb(41, 28, 28);
}
#screen{
    height: 38px;
    width: 273px;
    margin-top: 30px;
    margin-left: 8px;
    pointer-events: none;
}
.btn{
    margin: 12px;
    height: 33px;
    width: 40px;
    margin-left:17px;
}