calStyle.css

html {
    box-sizing: border-box;
}
*, *:before, *:after {
    box-sizing: inherit;
}
body {
  padding: 30px;
  margin: 0;
}

/* parent class */
.wrapper {
    display: grid;
    width: 400px;
    border: 1px solid #ccc;  
    border-radius: 5px;
    background:#1C1C1C;
}

.calculator-screen{
    display: block;
}

.calculator-buttons{
    display: grid;
    grid-template-columns: repeat(4,1fr);
    border: 0;
    grid-gap: 1em;
    padding: 20px;
}

input[type=text]{
    margin-top:20px;
    padding: 20px 30px 20px 20px;
    font-size:30px;
    color:white;
    text-align:right;
    background:transparent;
    border:none;
    width: 400px;
}

.button{
    font-size:2em;
    height: 65px;
    width: 65px;
    background-color:#505050;
    color: honeydew;
    border-radius: 50%;
    border: 1px solid #c4c4c4;
    text-shadow: 1px;
}

.btnExtraWidth{
    width: auto;
    border-radius: 30px;
}

.clear:hover {
    background-color: #f0595f;
    border-color: #b0353a;
    color: #fff;
}

.orange{
    background-color:#FF9500;
}

.span{
    grid-column: span 2;
}

button:hover {
    background-color: #D4D4D2;
    color: #505050;
    border: 1px solid #505050;
}

button:active{
    color: honeydew;
    background-color: mediumseagreen;
}