html {
    height:100%;
}

body {
    margin:0;
}

.bg {
    animation: slide 6s ease-in-out infinite alternate;
    background-image: linear-gradient(45deg, var(--colortercero) 40%, var(--colorsegundo) 60%);
    bottom: 0;
    left: -50%;
    opacity: .5;
    position: fixed;
    right: -50%;
    top: 0;
    z-index: -1;
}

.bg2 {
    animation-direction:alternate-reverse;
    animation-duration:7s;
}

.bg3 {
    animation-duration:8s;
}

.content {
    background-color:rgba(255,255,255,.8);
    border-radius:.25em;
    box-shadow:0 0 .25em rgba(0,0,0,.25);
    box-sizing:border-box;
    left:50%;
    padding:10vmin;
    position:fixed;
    text-align:center;
    top:50%;
    transform:translate(-50%, -50%);
}

@keyframes slide {
    0% {
        transform:translateX(-25%);
    }
    100% {
        transform:translateX(25%);
    }
}