webdroid/css/main.css

@font-face {
    font-family: 'Lato';
    src: url('fonts/Lato-Regular.ttf');
    src: url('fonts/Lato-Regular.ttf') format('truetype');
}

* {
    box-sizing: border-box;
    padding: 0;
    margin: 0;
}

body {
    display: grid;
    grid-template-columns: 1fr;
    grid-template-rows: 1fr;
    width: 100vw;
    height: 100vh;
}

main {
    display: grid;

    background: #0002;
}

.grid.center {
    place-content: center;
    place-items: center;
}

.btn {
    
}
.btn:focus {
    outline: none;
}

.btn.cbtn {
    display: grid;
    place-content: center;
    place-items: center;
    position: relative;
    
    padding: 2.2rem;
    margin: -.4rem;

    width: 0;
    height: 0;

    border: none;
    background: none;
    color: #000;
    font: unset;

    border-radius: 100vw;
}
.btn.cbtn::after {
    content: "";
    position: absolute;
    z-index: 1000;

    padding: 0rem;

    width: 0;
    height: 0;

    border-radius: 100vw;

    backdrop-filter: invert(1);
    transition: padding .2s;
}
/* When deployed on a platform, choose one or the other, not both */
.btn.cbtn:focus::after, /* TV */
.btn.cbtn:hover::after  /* PC */ {
    padding: inherit;
}

@keyframes cbtn-click {
    from {
        padding: 0rem;
        opacity: 1;
    }
    to {
        padding: inherit;
        opacity: 0;
    }
}
.btn.cbtn > .click {
    position: absolute;
    padding: 0rem;
    opacity: 1;
    z-index: 10000;

    border-radius: 100vw;
    width: 0;
    height: 0;

    /*box-shadow: inset 0 0 2px #FFF;*/
    background: #DDD8;
    border: 4px solid #fff;

    animation: cbtn-click .2s;
}

.btn.sbtn {
    padding: 1rem 2rem;
    text-align: center;
    text-decoration: none;
    font-family: Lato;
}
.btn.sbtn::after {
    
}