body{
    text-align:center;
    margin: 0;
    padding: 12px;
    box-sizing: border-box;
}

.btn{
    height:200px;
    width:200px;
    border: 10px solid black;
    border-radius: 20%;
    margin:2.5rem;
}

.btn-container{
    display: flex;
    justify-content: center;
}

.yellow{
    background-color: #f99b45;
}
.red{
    background-color: #d95980;
}

.green{
    background-color: #63aac0;
}

.purple{
    background-color: #819ff9;
}

.flash{
    background-color: white;
}
.userflash{
    background-color:green;
}

@media (max-width: 600px) {
    h1 { font-size: 1.6rem; }
    h2 { font-size: 1rem; }
    .btn {
        width: min(34vw, 150px);
        height: min(34vw, 150px);
        margin: 6px;
        border-width: 6px;
        box-sizing: border-box;
    }
}