site/_src/_assets/styles/bigchain/_nyan.scss

.nyan {
    position: relative;

    &:before {
        content: '';
        position: absolute;
        left: 0;
        right: 0;
        top: 0;
        bottom: 0;
        background: url('../img/nyan.gif') no-repeat left center;
        background-size: 50%;
        z-index: 0;
        opacity: 0;
        animation: nyan-appear .6s ease-out forwards;
    }

    code {
        position: relative;
        z-index: 2;
    }
}

@keyframes nyan-appear {
    0% {
        opacity: 0;
        transform: translate3d(-5rem, 0, 0);
    }

    100% {
        opacity: .4;
        transform: translate3d(0, 0, 0);
    }
}