The financial terms of the deal were not disclosed, but Zynga described it as a "small acquisition."

A Bit Lucky will help Zynga move from its focus on casual games to a new category of midcore, multiplatform games.

Midcore gaming is the market segment comprised of players looking for a more in-depth experience than a casual game, yet one that is not as time-consuming as a core game, according to Newzoo, a market research firm focused on the gaming industry. It estimated in April that the market for midcore gaming is over US$2 billion in the U.S. and Europe.

Zynga executive Bill Jackson said in that he is "excited to share some news about a new category that you may have heard us hint at before: mid-core, multi-platform games."

All the over 20 staff of A Bit Lucky in San Mateo, California, will join Zynga in San Francisco, according to the blog post.