.fondo {
    background: linear-gradient(-45deg, #468df9, #76b5f3, #29bdb2, #23d5ab);
/*    background: linear-gradient(-45deg, #ffcd00, #001f7e, #d00c27);*/
    background-size: 400% 400%;
    animation: gradient 15s ease infinite;
    height: 100vh;
}
  
@keyframes gradient {
    0% {
        background-position: 0% 50%;
    }
    50% {
        background-position: 100% 50%;
    }
    100% {
        background-position: 0% 50%;
    }
}