Ok the first 5; finished & released. I got the feedback I need, and the reviews were satisfying enough so I got enough motivation to make the other 5 (or more) as well. I'm now trying to think of some raw ideas for the following levels. Any suggestions would greatly be appreciated.

Note: I think in the final pack I'll make two versions of each level. The original version for multiplayer online and a single player version with enemies and probably save points & more ammo.