#fondo{
    height: 500px;
    width: 100%;
    background-image: url(imagenes/fondo4.jpg);
    background-repeat: no-repeat
}

#boton-arriba{
    width: 60px;
    height: 60px;
    background-color: blueviolet;
    display: flex;
    justify-content: center;
    align-items: center;
    color: white;
    border-radius: 50%;
    font-size: 20px;
    position: fixed;
    bottom: 50px;
    right: 50px;
    cursor: pointer;
    border: 4px solid transparent;
    transition: all 300ms ease;
    transform: scale(0);
}

#boton-arriba:hover{
    transform: scale(1.1);
    border-color: rgba(0, 0, 0, o.1);
}