style.css

*{
     user-select: none; /* supported by Chrome and Opera */
    -webkit-user-select: none; /* Safari */
    -khtml-user-select: none; /* Konqueror HTML */
    -moz-user-select: none; /* Firefox */
    -ms-user-select: none; 
}
.container{
max-width: 400px;
margin: 10vh  auto 0 auto;
border: #100;
box-shadow: 0px 0px 43px 17px rgb(155, 155, 155);
}

#Screen{
    text-align: right;
    height: 70px;
    line-height: 70px;
    padding: 16px 8px;
    font-size: 25px;
}

#buttons{
    display: grid;
    border-bottom: 1px solid #999;
    border-left: 1px solid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
}

.buttons>div{
    border-top:1px solid #999;
    border-right: 1px solid #999;
}

.button{
    border:  0.5px solid #999;
    line-height: 100px;
    text-align: center ;
    font-size: 25px;
    cursor: pointer;
    transition: 0.5s ease-in-out;
}
.button:hover{
    background-color: #323232;
    color: rgb(255, 255, 255);
}