The game is nice, but a lot too easy (according to me). I won't finish it cause I reached level 15 and I got 3 stars on every level without difficulty, and without changing of strategy, and I think the game should be harder sooner, else it become a bit annoying also cause levels are a lot similar.
But maybe it's not the game that is too easy but the bunny that is too unbalanced. I started the game by taking the bunny and the snail, so I was able to spam resistant bunny and then I only add to upgrade the two and just spam bunny and snail. Once the bunny is level 3 and you have 2 on the board with a snail, the opponent can't do anything.
music is nice
edit: if you say there is an unit to counter it, it's fine. but maybe make it appear before level 20 :)