1. My game would look/sound totally different, but I would like to reuse the level design, because with the given gameplay mechanic the creation of levels is very very complex.
2. Can I do that?
3. Has there ever been a court case where ONLY the abstract level design had been copied?
1. So you're saying you are incapable of doing this very very complex thing? Or you're just saying "it's too hard"? Then maybe you should make some other kind of game.
2. You CAN do that. But is it a good idea? That depends on your comfort level with risk.
3. Maybe, maybe not. How comfortable are you with there being one, with you as the defendant? The advice we've given is that it's best to do what jbadams says:
[quote name='jbadams']
You should always check with your lawyer if you want to be more sure.[/quote]