I just...
... stopped playing 'cause of the birds. They just get passed my catapults and bomb an empty place where I can't build anything. Moreover, where a ground unit would take several hits to destroy a turret, these damn birds blow it up in ONE bomb. So, they're glitchy, and too powerful (in my opinion), and I recommend you get them checked to prevent other people to hate them lie me.
Other than that, this game is a really good sequel to the first one. The gaphics are wayyyyy better, the gameplay is cool toough similar to Plant VS Zombie (like someone said before) and the oil idea is quite cool, and there seems to have many more level. Though I didn't finish it beacause of... You now what.
So, yes a great game but those devilish birds have to be sent to hell where THEY can be bombed for eternity, over and over again. F*ck them !