This is a really good game. I love the idea of a mailbird rushing around to deliver packages at lightning speed and the controls are pretty good as well.
I do however think there should be more going on in the background. I say this because I really liked the art style for the assets you made like the level select map and character, and I don't know if you ran out of time, but I wish the levels were a bit more lively. Also, the music seems to only play at the start of the level for some reason and fades the further away the player get.
I hope this comment doesn't come across as negative as I don't mean to be. As I said before, the game is really good and I think you did a great job (especially for the time given), I'm just trying to give some constructive feedback on how I think it could have been even better.