Let me start by saying this was exactly what I was looking for when I began looking through the hl2 mods available here. For some reason I love any puzzle elements executed in the hl2 engine and enjoyed all the little puzzles you had to solve throughout the actual hl2 game itself and R&D pretty much mixes all those great moments into one sweet package.
Research & Development pretty much a perfect mod for any fps puzzle lovers and the only thing I can hope for now is a sequel :D