What a cute game! It's a simple mechanic, and I think your description understates how you're "joining together" a variety of ingredients to cure the cat's curse! You could probably create an endless number of levels through some kind of programming magic, but it also works great that there's only a few levels, so it doesn't get old. Leaves me just wanting more!
Just a small thing - it would be nice to delay showing the first potion ingredient until a second or so after the level has started. Otherwise it's easy to miss that first ingredient, and then you have to wait through the entire list of ingredients until you can get started.