Hey nice little game that. Nice graphics and good, smooth gameplay. My only issue was with the fixed 16:9 aspect ratio, but assume that'll be changed before the final release!
One other thing that may make the controls a tad more fluid would be instead of holding to power up your shot, make it swipe to give the user more control. Later in the game (where the metal things come) I was struggling to shoot over them to make them drop as I couldn't get the right amount of power. Probably one of those things that you get used to after playing it lots.
Anyway, good luck on the final release!