While the style of the game is fine and the game itself runs smoothly, I have to say that the level of difficulty curve is WAY to steep at the start. The enemies took too long to kill before they built up in sufficient numbers to make dodging almost impossible. It took me several tries just to get enough points to boost my energy so I wasn't sniped out of the sky under 5 seconds.
Once I finally got past that first stage, it felt like I was starting all over on the next level. There are also two blind spots: 1) the enemy-spawning shed on the level, under which they can hide and you can't hit them and 2) the opposite wall due to robobird's wingspan (enemies are small enough to hide in it). My recommendation for this is to add some sort of dodge mechanism to make avoiding enemy fire easier (robobird is too large) and to address the difficulty scale.
Otherwise, nice job.