Good Start
Good start, but it needs some work.
Two main points really:
1) When you destroy an enemy, the destroyed ship seems to appear randomly over the screen, rather than where you shoot at it - quite disorientating when there are more than one enemy.
2) It's very hard to get far in the game when the enemies dont enter 'firing range' until the second they start shooting at you!
It generally needs a tidy up, and made more interesting. Make a it more obvious when you shoot an enemy, make some different enemies etc.
Keep trying!