Casual gaming developer PopCap Games, which has recently made forays into mobile gaming, has acquired Retro64, a site that provides downloads of old-style arcade games. Retro64, which is headquartered in Chicago, also markets a series of action and puzzle games, which Seattle-based PopCap feels will round out its product line. The merger, the terms of which were undisclosed, followed PopCap’s publishing of Retro64’s Venice game, which lets players search for underwater treasure while navigating a gondola in a computerized version of the Italian city. Release