.scroll-to-top {
position: fixed;
right: 75px;
bottom: 75px;
width: 70px;
height: 70px;
z-index: 99;
display: block;
border: 4px solid #c1c1c1;
font-size: 42px;
border-radius: 50%;
color: white;
opacity: 0;
transition: .5s;
background-color: transparent;
color: #c1c1c1;
}

@media (hover: hover) {
    .scroll-to-top:hover {
    background-color: #c1c1c1;
    color: white;
    }
}

@media screen and (max-width:568px) {
    .scroll-to-top {
        right: 40px;
        bottom: 60px;
        width: 60px;
        height: 60px;
        font-size: 36px;
    }
}