Zynga may have paid at least $20.5M for Challenge Games, SEC filing shows

Zynga may have paid at least $20.5 million for Challenge Games, the Austin-based social gaming startup it said it purchased yesterday, according to an SEC filing.

Challenge Games raised $14.5 million in venture funding in two rounds from Sequoia Capital, Globespan Capital Partners and other investors. It’s hard to gauge investor returns, however, since there might be additional capital involved in the transaction on top of the $20.5 million suggested in the filing.

Challenge Games has built Web-based games such as Warstorm and Ponzi on a virtual-goods business model, where players buy digital trinkets to advance in the game. It will be turned into Zynga’s Austin office following the transaction.