.container{
    display: inline-block;
}
.container .button{
    width:4em;
    height:4em;
    font-size:24px;
}
.container .button.text-Clear{
    width:12em;
}
.container .button.text-0{
    width:8em;
}
.container .output{
    height: 4em;
    font-size:36px;
    position: relative;
    border:grey 1px solid;
}
.container .output span{
    position: absolute;
    right:0.4em;
    bottom:0.4em;   
}
.author{
    margin-top:10px;
}
.author span{
    font-size:16px;
}
body{
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;    
}