#cat {
    animation-name: walking;
     animation-duration: 8s;
     animation-fill-mode: forwards;
     animation-iteration-count: infinite;
}

@keyframes walking{
    0%{
        transform: translateX(0px);
    }
    48%{
        transform: translateX(600px);
    }
    50%{
        transform: rotateY(180deg) translateX(-600px);
    }
    98%{
        transform: translateX(0px) rotateY(180deg);
    }
    100%{
        transform: translateX(0px);
    }
}

/*solution*/
article {
    position: relative;
}

article section {
    position: absolute;
    top: 2.44em;
    width: 700px;
    left: -700px;
    padding: 0 1em 0.5em 0.5em; 
    background-color: #9be2dc;
    transition: transform 0.5s;
}

article section nav {
    width: 110%;
    text-align: right;
    padding: 0.5em;
}

.visible {
    transform: translateX(690px);
}

img {
    width: 250px;
}

h1 {
    color: rgb(165, 60, 210);
}