#backtotop{
    z-index:999; 
    display:flex; 
    align-items: center;
    justify-content: center;
    position:fixed; 
    visibility:hidden; 
    bottom:20px; 
    right:50px; 
    width:50px; 
    height:50px; 
    line-height:36px; 
    font-size:16px; 
    text-align:center; 
    opacity:.2;
    text-decoration: none;
    border-radius: 100px;
    background-color: #0055b2;
}
#backtotop i{
    font-size: 30px;
    color:#fff;
}
#backtotop.visible{
    visibility:visible; 
    opacity:.5;
}
#backtotop:hover{
    opacity:1;
}