The defense building mechanic was a little difficult to work. I ended up just building as many squirrel turrets as I could at the very beginning and just racing as far ahead as I could. I didn't see any way to accumulate more money after that, so it was just a waiting game until the squirrels won for me. Maybe there was another defense that would have helped?
Overall, I liked it. A bit more time to work out some of the details, and this would make a neat full game.