I really like the graphics and the view and everything a lot. Sure it doesn't look realistic but it has a lot of style and looks awesome!
I thought that the enemy design could use a bit of work at the moment. Most of the enemies seemed to be the ones that flew in from behind and just directly past you. I wasn't really sure if they were supposed to be enemies or not because they were flying in from behind and flying right past me without shooting. I figured I was supposed to shoot at them because they were the only things on the screen, but I didn't feel like I was under attack, it was more like I was losing at an airplane race. I think that the game might work better (and makes more sense to me) if most enemies came in from the front.
I didn't really realize I could overheat my weapon until the boss. That's a good idea but it's hard to tell when the gun is going to overheat, the indicator just turns red at a certain point after shooting too long. Maybe have the indicator slowly change from gray to red as the player is firing so they can know when to let up on the gun.
The boss seemed like he had way too much health. I filled many many bullets/missiles into him and it just felt like it was taking forever. He doesn't have a lot of variation at the moment so it's easy to lose interest quickly. There also seemed to be some positions on the screen where I could just stay there and be perfectly safe. I really liked the ending screen whenever you beat him, it was really funny.
I found it really funny that the player picks up ice cream, soda, etc in an airplane to regenerate health.
Overall, I thought it was really good so far.
It seems like it has potential to be a very awesome game! I'm interested in checking out some more updates once you have them!