Very nice game. Some interesting strategy elements that come into play early in the game. One of the drawbacks, in my opinion, is when you go to create the higher level critters, having to go back and create lower level critters first (if there were a way to simply take the resources if you have them rather than having to always create a bunch of critters first that would be preferable).
Potential bug: Not sure why this is happening but I cannot seem to initiate the third star difficulty for levels 14, 30, and 31 (I can click on 1st and 2nd star; however, if I try to click on 3rd star first, I cannot click on 1st and 2nd star).