In a counter-move against Zynga, game maker PopCap Games said today that it has acquired the San Francisco-based social game developer ZipZapPlay. Terms of the deal were not disclosed.

The move could be one of the first for a more aggressive PopCap, the Seattle-based maker of hit games from Bejeweled to Plants vs Zombies, as it tries to be more competitive in social games on Facebook, where Zynga dominates. San Francisco-based Zynga opened an office to recruit game developers in Seattle recently, and now PopCap is acquiring a game studio on Zynga’s home turf. It’s kind of like a tit for tat move in a very high stakes battle for the future of social games.