That was pretty fun for awhile, but it needs work. You've gotten a solid foundation set up for a potentially great game. I hope you keep working on it and submit it later. If you do decide to do that, here are a few suggestions for improvement:
Further increase the weapon power and type. Being able to being able to increase the weapon power is a great idea. Keep making the power bonuses stack up. For example, first start off with one stream of bullets (like you already did) increase to two streams of bullets (again, like you already did) and a third stream after another power pickup. Then when the next bonus is picked up, maybe one stream of rockets, increasing to two streams after the next pickup, etc.
That being said, various opponents would be nice. Not just all one plane with one strength. Maybe some planes that take more hits (making the improved weapons necessary) and that shoot better weapons (like slow moving guided missiles that you have to shoot in order to stay alive). Also, if you add music and sound effects, that would make it much better. Perhaps some different levels, and a storyline as well.
Just some suggestions if you decide to continue this project. I hope to see the next version come out!