*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-color: grey;
}

.container {
    border: 1px solid #ccc;
    border-radius: 20px;
    position: absolute;
    top :50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 325px;
}

.screen {
    width: 100%;
    border-top-left-radius: 20px;
    border-top-right-radius: 20px;
    font-size: 3rem;
    height: 80px;
    border: none;
    background-color: transparent;
    color: #fff;
    text-align: right;
    padding-right: 20px;
    padding-left: 10px;
}

button{
    height: 60px;
    border-radius: 20px;
    border: 1px solid #c4c4c4;
    background-color: rgba(0, 0, 0, 0.3);
    font-size: 2rem;
    color: #f8f8f8;
}

button:hover{
    background-color: rgba(255, 255, 255, 0.4);
}

button:active{
    background-color: rgba(186, 186, 186, 0.4);
}

.all-clear:hover {
    background-color: rgba(241, 115, 119, 0.4);
}

.equal-sign{
    height: 100%;
    grid-area: 2/4/6/5;
}

.equal-sign:hover {
    background-color: rgba(78, 159, 212, 0.4);
}

.keys {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    grid-gap: 10px;
    padding: 10px;
}