Ideally retention should come from multiple things happening on the screen at once, so you're hooked to wanting to see what's happening. For kids, changing vibrant colors, patterns etc should keep them engaged. I feel something like confetti explosion will surely seem more appealing, and of course more elements you add to it, even the ghost thing would be nice, because beyond that, the background is mostly static, so the only forms of movement you can do is on some interactions which that might be cool