I am sorry if this seems harsh but the game needs quite a lot of improvements.
1) Never make Z to jump or X to shoot. Awkward controls.
2) One shot and your dead? No! Don't do that. Make it so you can have a healthbar and you can regain health.
3) Powerups: Such as ew weapons or a shield.
4) Please add a double jump rather than shooting the ground whilst in mid-air. It doesn't feel correct, espicially when, personally, the controls are awkward.
5) Add a varied background or platform design. Don't keep it boring old green. Makes the game look boring.
One good thing:
Like the retro graphics. They definately remind me when platformers were just starting to become popular.
All in all 0.5 / 5. The game needs work and seems unfinished.