It's great. I love this genre. The colour system needs a little work, it would be nice if a different colour appeared if that combination was already made, but then it might be easier. I do like Doodle God's hint system, how you have to wait for a hint and only use it if you want. Also, maybe a sort of family tree would be good, like as another menu, so you can view what you have and see what you haven't combined yet.
Also. For us people who just get stuck, even after combining things with the same thing, can we have a walkthrough. I'm really stuck :(
Otherwise superb game. I will want to know when a newer version comes out!