This game is very linear. Each enemy has a very specific tower that kills it. Just wait for that enemy then place that tower. Then the next enemy, next tower. Theres NO extra money to upgrade or buy towers. Only what you HAVE to buy at a particular moment. The only strategy in this game is where to place your towers since they pretty much tell exactly which tower to buy at exactly which time. The only reason this gets 2 stars is because the graphics are incredible and I like to support games that dont have any IAPs. I read a few reviews that talked about the linear problem but thought Id give it a try. Wish Id saved my money.