Oh my, 10 people in the team ? Damn ^^ !
Nice game ! The base mechanic embraces the theme perfectly (with some "Final Fantasy Cristal Chronicles" vibes), and the game is really enjoyable to play ! The gameplay is cool, it's a good shooter with a lot of neat features =). My only complain about the controls is that either the character is a bit too slow (even with the upgrade) or the maps are too big.
The upgrade system is a really nice addition ! However, I upgraded my damage from something like 4 to 5, and the next bird wanted me to upgrade from 2 to 3... Is that a bug, or do I misunderstand something ?
The music is really cool ! Is it dynamic ? Maybe it's my imagination, but I think I heard some variations here and there ^^.
The visuals are pretty good, the character is cute (but maybe a bit pixelated in game. Maybe the original sprite needs to be resized to avoid compression ^^ ?) and the light effect is really nice !
Overall, that's a really solid entry, congratulations to the team ! I would love to play a more polished version, with more diverse levels, weapons and feature =p !