I played around 10 rounds of this with the default character, and think it's well-done, with only one issue.
I love the graphic art style and the sound design. I also think that this is perfect for the mobile platform; it lends itself to replayability quite well with the short play sessions. What program did your team use to compose the music?
As for the only problem I have, the game's general aesthetic seems to be retro, suggested by the music, graphics, and some of the sound effects. The glaring issue comes in with the sound effect played upon a bird-to-bird collision; it's an analog pinball machine bumper! While I realize that you're trying to convey that two objects bounce apart upon collision, the analog, realistic sound effect contrasts with the retro-style limitations. I suggest creating a new sound effect in your music composition program which conveys the bounce while adhering to the aesthetic. Try listening to the NES "Pinball" audio for inspiration. Otherwise, this game is excellent.
Thank you for creating this game, and I might just pay this a download on Android.