squirrel-theme/css/totop.css

.totop {
    display: inline-flex;
    background-color: Tomato;
    color: #f2f2f2;
    width: 50px;
    height: 50px;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    margin: 30px;
    position: fixed;
    bottom: 0px;
    right: 0px;
    transition: background-color .3s;
    z-index: 1000;
}

.show {
    visibility: visible;
    opacity: 1;
}
  
.hide {
    visibility: hidden;
    opacity: 0;
}

@media screen and (min-width: 600px) {
    .totop:hover {
        cursor: pointer;
        background-color: black;
    }
}