8 levels, designed to be played solo (although not together). (These are 8 of the 19 in the Infinity version.) A bit linear at first... but good for a bit of carnage, if that's what you're looking for. No real plot on any of 'em.

Construction looks interesting, gameplay is fine, for what I could see... unfortunately, there are too many one-shot doors. Twice I got to a place I couldn't continue because I'd opened a door and not immediately gone through. That's one time too many for me... Four levels, if you can get that far.