*{
    text-align: center;
}
.btn-container{
    display: flex;
    justify-content: center;
}
.btn{
    border-radius: 20%;
    border: 6px solid black;
    width: 200px;
    height: 200px;
    margin:2.5rem;
}

.yellow{
    background-color: rgb(250, 148, 5);
}
.green{
    background-color: rgb(4, 136, 136);
}
.purple{
    background-color: rgb(34, 104, 226);
}
.red{
    background-color: rgb(223, 5, 121);
}

/* Flash animation */
.flash{
    background-color: white;
}
.userflash{
    background-color: green;
}

@media only screen and (max-width: 600px) {
    .btn{
        width: 150px;
        height: 150px;
        margin: 1.5rem;
    }
}