Canvas example

<canvas id="canvas"></canvas>
<script>
    const canvas = document.getElementById("canvas")
    const ctx = canvas.getContext('2d')

    ctx.fillStyle = "#ff0000"
    ctx.fillRect(20, 20, 100, 100)

    const canvasurl = canvas.toDataURL('image/png')
    let bg = new Image()
    bg.src = canvasurl
    ctx.drawImage(bg, 0, 0)

    let x = 0
    const main = () => {
        ctx.fillStyle = "#000000"
        ctx.fillRect(0, 0, canvas.width, canvas.height)
        ctx.drawImage(bg, 0, 0)

        ctx.fillStyle = "#00ff00"
        ctx.fillRect(x, 40, 20, 20)
        x += 0.3

        requestAnimationFrame(main)
    }
    main()
</script>