If you've ever played the game 1942, you'll come away from this game slightly disappointed.
I played part 1-1 Here the enemies move quickly downscreen, and don't give you much of a chance to shoot them. Generally it's a rather unthreatening collection of foes, as they don't stick around enough to do much damage, nor do they move about enough to dodge attacks.
So I shuffled along to part 1-3. New and better foes. The volcanoes blended worryingly well into the background, but were good fun.
The game overall is alright, and it has great potential. I would seriously recommend looking at 1942, or one of it's sequels, also worth a look (further up the difficulty scale) are bullet hell games.
What you have here is good, and it feels like a pretty solid foundation for something better. I really want to see that happen, because this sort of game can seriously rock when done well. I like the art style, and the music, and the controls, I even like the enemies. But I want more, more interesting enemy paths, more bullets, more destruction, more evasion, more everything. And if you look at what's already out there, I think you can do that.