body {
    max-width: 500px;
    margin: 2em auto;
    padding: 0 1em;
    font-size: 20px;
    text-align: center;
}

h1 {
    margin-bottom: 1em;
}

.box {
    width: 100px;
    height: 100px;
    background-color: coral;
    margin: 1em auto;
}

@keyframes moveBox {
    0% { transform: translateX(0); }
    100% { transform: translateX(300px); }
}