PC gaming super-blog Rock, Paper, Shotgun loves R&D! In a new review Alec Meer praises the mod as "a seismic shift" away from the norm, telling readers that it is "as must-play as an HL2 mod gets":

R&D’s hook is that it’s essentially non-combative. Yep – you go without guns throughout (bar the ol’ Gravity jobbie, but hey, that’s more about construction than destruction here). Sure, you can tell an Antlion to claw someone to death or arrange to squash men with falling girders, but you’re definitely not Edward Pistolhands. It’s an environmental adventure game, taking the irregular physics and logic puzzles seen in HL2 itself and turning them into the game itself. Mazes, gravity, exploding microwaves and fire-retardant antlion carapaces all make an appearance – it’s very much a point’n’click adventure in an FPS engine.

If you still haven't played Research and Development, which requires Episode Two, download it now!

Update: Destructoid also has a very positive review.