Maybe this is just me, but I think it was a bit too hard. When you have to spend 10 minutes on one level it isn't fun anymore.
I also think there should be upgrades, on the canon, the pig, and maybe other upgrades too. And bonuses. Bonus for flying really fast, bonus for flying really high, bonus for getting 10 things of the same kind on a row... Stuff like that.
Other than that, I really like the idea. The pig was cute, and the music was ok. But I do think this has great potential. I'd give it a 3/5.
I really liked this game. I love games that has a deeper/hidden meaning to it, that makes you think - like this game did. I also loved the music! So, all in all: well done! (But please, do not remove the "road closed" sign. I know for sure this game won't be as good as it is now if you did that. Then it won't have any meaning, but with it, it does have a meaning. A great meaning!)