如何使用纯CSS 实现一个没有DOM元素的动画效果

body {
    position: fixed;
    margin: 0;
    width: 100vw;
    height: 100vh;
}

body::before {
    content: '';
    position: fixed;
    width: 200vmax;
    height: 200vmax;
    background-color: steelblue;
    color: turquoise;
    background-image: 
        linear-gradient(
            45deg, 
            currentColor 25%, 
            transparent 25%, transparent 75%, 
            currentColor 75%),
        linear-gradient(
            45deg, 
            currentColor 25%, 
            transparent 25%, transparent 75%, 
            currentColor 75%);
    background-position: 0 0, 5vmax 5vmax;
    background-size: 10vmax 10vmax;

body::before {
    top: 50%;
    left: 50%;
    animation: 
        9s move infinite ease-in-out alternate;
}

@keyframes move {
    from {
        left: -40%;
        top: -40%;
    }

    to {
        left: -60%;
        top: -60%;
    }
}

body::before {
    animation: 
        9s move infinite ease-in-out alternate,
        9s -1.5s rotating infinite ease-in-out alternate;
}

@keyframes rotating {
    to {
        transform: rotate(180deg);
    }
}

body {
    top: 50%;
    left: 50%;
    animation: 
        3s move infinite ease-in-out alternate;
}

body {
    animation: 
        3s move infinite ease-in-out alternate,
        3s zoom infinite ease-in-out alternate;
}

@keyframes zoom {
    to {
        transform: scale(10);
    }
}

@keyframes rotating {
    to {
        transform: rotate(180deg);
        filter: hue-rotate(1turn);
    }
}