[X] do graphics for StrongerGuns and StraightGuns
[X] graphics of our own spaceship, it's still ugly
[ ] increase enemy level over time in single player
[X] probabilities for item drops
[X] MULTIPLAYER
[X] documentate
[ ] balance
[ ] sounds
[ ] smaller spaceships
[ ] many more kinds of enemies
[ ] HP loss when letting spaceships pass
[ ] scoring
[ ] complex AI
[ ] more awesome graphics
[ ] more than one level, upgrade shop in between
[ ] multiplayer over internet