Too easy to beat. You need more music tracks. Not worth 2 bucks even with a soundtrack and poster. No offense but the rush to merchandise something with only 1 song, 1 level and only 3 enemy types seems a bit premature. Focus on creating a setting instead of using speedlines and fog. Create a reason for the hero to be there before you create a cult of personality around them. You have a cool art style but it's not R-Type.
The bomb types are an original concept but why not create a level up system around boss kills for your gun? Keep the powerups the same but every time a boss pill appears let the player choose between spread, homing and power. How about making some new baddies that steal power ups, or even some that represent them like green armored dudes or white shotgun dudes or blue ice dudes? Why not make some mutated style enemies based on old 80s death metal album art?
I liked the fact that you could activate it after 3 powerups but why not create a saving system where 3 is the minimum, but 9 is the maximum? That way you could blast them that much harder. Why not create a circle of protection overlay for the shields so you have a more gothic magic feel?
This might seem like im slamming you but you have killer potential. The code is tight and the art is solid, you just need more content to make this a 5 star game.