I really like the conceptual base of the game, but I think there can be a few tweaks to be made in order to make it easier to play and more enjoyable for the player. I think that the enemies can start out a little slower in order to give the player a chance to adapt to the gameplay, and in general, I think the difficulty curve can be reduced to make it easier to play and get experience in and slowly ramp up the difficulty over time. I agree with arfox in that I think that making the player able to move around could be very interesting to the game. I think more tradeoffs could be made using the idea of growing with the number of bullets you shoot, and I think there should be a way to reverse that change (maybe get smaller the more enemies you kill?) so that you have to constantly manage your size. Overall, I love the idea, and I'm waiting for more to come!