Keen eyes have spotted something juicy in one of the presentation slides shown during a recent Xbox 360 event at a campus in Spain. The large central box in the “XNA Technology Map” slide is labeled, “Game Engines.” One of the items in that list is “Valve: Half-Life 3.” Keep in mind that this mention is just of the game engine, not the actual game. But still, this gives us reason to believe that Valve might be interested in the Xbox 360, despite the fact that its big man, Gabe Newell, recently expressed his concerns about developing games for the 360 and PS3.