Thanks for the suggestions and new ideas.
Now the ammo are skulls - maybe they make more sense?
The level are played - like in PAC-MAN one after the other.
There are four levels now to play.
If you exit one (kill all ghosts->get exit key->goto door->next level) you enter the next.
Or is there a problem on your side with the level changing? Please report!
The spikes are now not that 'killing' :)