I've started creating the mod, now I'm doing the first level in Chapter I. Chapter I is taking place in a medium-size underground lab-system (Corpuscle Lab). You are a researcher, and you're working on a gravity-gun.
You are the one, who has the right to test it, when it's in 'beta' state. When you've finished with the testing, something goes wrong, and you have to escape from the lab. This escaping through the Corpuscle Lab is Chapter I. Here will be no enemies, just puzzles.
So this is what I'm working on these days.