body{
    margin: 0;
    padding: 0;
}
.mainContainer{
    display: flex;
    justify-content: center;
    align-items: center;
    align-self: center;
    width: 100vw;
    height: 100vh;
    background-color: black;

}

.Box{
    width: 75px;
    height: 75px;
    margin: 10px;
    border: 2px solid black;
}

#redBox{
    background-color: red;
}
#blueBox{
    background-color: blue;
}
#yellowBox{
    background-color: yellow;
}
#greenBox{
    background-color: green;
}