This game was really fun! I would have though it is hard to make a good feeling roguelite progression in such a short time but this game nails it! And the way you can advance your starting position so that, when you are more powerful you can get straight to the proper action, instead of just running through all the low level birds. I also found myself thinking about what birds to shoot and when to either save bullets or maximize the feathers gained with each shot, or to try and save them to the boss.
There is so much polish in the game, yes there might be a few things here and there to fine tune, but nothing that major that would make the game less fun. The boss fight in the end, how the other birds gather around, and how the flying shadow has been guiding you towards that the whole time.. Excellent! What an amazing game! Well done!