Play it.
RD is one of the best HL2 mods out there. I played it today and couldn't stop, from start to finish i was hooked. This is how a mod should be, he didn't create it in 2 months and he didn't take 6 years either (NMRiH, im looking at you! joking of course). These puzzles absolutely destroy Valves attempts in the Half Life series, and even Portal.
Yes, its that good.