main.css

@import url('https://fonts.googleapis.com/css2?family=Roboto+Slab:wght@100;200;300;400;500;531;600;700;800;900&display=swap');

* {
    margin: 0;
    padding: 0;
}

body {
    background-color: #fe7;
    display: flex;
    justify-content: center;
    z-index: -1;
}

.white-keys {
    z-index: 0;

}

.white-keys kbd {
    position: relative;
    display: inline-block;
    margin-left: -5px;
    background-color: white;
    width: 30px;
    height: 120px;
    text-align: center;
    line-height: 185px;
    border-width: 2px;
    border-style: solid;
    border-color: grey;
    border-image: initial;
}

.black-keys {
    position: absolute;
    margin-top: -123px;
    margin-left: 12px;
    z-index: 1;
    width: 200px;
    text-align: center;
    display: flex;
    flex-direction: row;
    justify-content: space-around;
}

.black-keys kbd {
    display: inline-block;
    width: 25px;
    height: 70px;
    text-align: center;
    line-height: 70px;
    background-color: black;
    color: white;
}

.container {
    margin-bottom: auto;
    margin-top: 25%;
    height: 120px;
}

#invisible {
    visibility: hidden;
}