#boton-ir-arriba {
    display: inline-block;
    background: #D3DBDE;
    border-radius: 50%;
    position: fixed;
    color: #5A5A5A;
    font-size: 20px;
    bottom: 20px;
    right: 20px;
    z-index: 100000;
    cursor: pointer;
    border: 4px solid transparent;
    transition: all 200ms ease;
    padding: 10px 16px;
    transform: scale(0);
    opacity: 0.8;
}

#boton-ir-arriba:hover {
    transform: scale(1.1);
    border: 4px solid #D3DBDE;
    opacity: 1;
}