style.css

body {
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0px;
    padding: 100px;
    background-color: black;
}

button {
    color: white;
    font-size: 30px;
    padding: 10px;
    border-radius: 10px;
    margin: 10px;
}

#container {
    background-color: grey;
    border-radius: 10px;
    display: grid;
    grid-template-columns: 100px 100px 100px 100px 100px;
    grid-template-rows: 100px 100px 100px 100px 100px;
    padding: 25px 25px 25px 25px;
}

#display {
    font-size: 50px;
    color: white;
    background-color: black;
    display: flex;
    flex-direction: column;
    justify-content: space-around;
    text-align: right;
    font-weight: bold;
    border-radius: 5px;
    width: 500px;
    height: 100px;
    grid-column-start: 1;
    grid-column-end: 6;
}

#grey {
    background-color: dimgray;
}

#orange {
    background-color: orange;
}

#light {
    background-color: lightgray;
}