This game (and its early stages in particular) sold me on puzzle maker, and its use case for making games with very simple goals for younger players, and I'm now using it to do the same for my own kid.
That said, the biggest potential for improvement here would be to use a different palette for the eggs and the stones. They're very similar in terms of both color and texture. I eventually saw that the outline distinguished them, but my kid—who felt more like the target audience—couldn't. Plus, it's a good habit to increase visual clarity of objectives.