body{
    text-align:center;
}
.btn{
    height: 200px;
    width: 200px;
    border-radius: 20%;
    border: 10px solid #000;
    margin:2.5rem;
}
.btn-container{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
}


.green {
    background-color: green;
}

.red {
    background-color: red;
}

.yellow {
    background-color: yellow;
}

.blue {
    background-color: blue;
}

.flash {
    background-color: white;
}

.wrong {
    background-color: red;
    opacity: 0.8;
}