*{
    font-family: cursive;
}
body{
    display: flex;
    flex-direction: column;    
    align-items: center;
    padding-bottom: 500px;
    cursor:default;
}
main{
    display: flex;
    border: 2px solid black;
    border-radius: 50%;
    height: 28rem;
    width: 28rem;
    position: relative;
    flex-wrap: wrap;
    overflow: hidden;
}
main div{
    height: 50%;
    width: 50%;
    border: black 1px solid;
    box-sizing: border-box;
    color: white;
    cursor: pointer;
    transition: opacity 0.15s;
}
main div:active{
    opacity: 0.5;
}
main .black{
    background-color: black;
    position: absolute;
    border-radius: 50%;
    top: 28%;
    left: 30%;
    height: 40%;
    width: 40%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.3rem;
    transition: scale 0.1s;
    text-align: center;
    user-select: none;
}
main .black:active{
    opacity: 1;
    scale: 0.8;
}
.green{background-color: rgb(32, 209, 32);}
.red{background-color: red;}
.blue{background-color: blue;}
.yellow{background-color: rgb(255, 255, 0);}

.flash{opacity: 0.1;}
.flash-red{background-color: red;}

.not-allowed-cursor{cursor: not-allowed;}