Kinda random generation of level

We have a few rules that the "random" level needs to abide by just to make the level completable. For example; if

• There must always be a way to succeed
• Difficulty should start low and increase over time
• Difficulty should never increase so much as to conflict with the first rule
• This means always more than a ship width between atleast two vertical asteriods
• And atleast a ship length between waves of asteroids.
• Asteroids should never overlap

Nifty Youtube vid by Jorge Rodriguez Here is a clever method for ensuring atleast the requirements are met.