Zynga has released Puzzle Combat, a free-to-play mobile game it calls a match-3 action role-playing game, worldwide on iOS and Android. The publisher, which trades on Nasdaq as ZNGA, says the game was built by Small Giant Games, the Helsinki studio it owns, and that players recruit heroes, build bases and fight one another in a zombie-themed setting.

The company is not pretending this is a new idea. Puzzle Combat takes the systems that made Small Giant's earlier game, Empires & Puzzles, work — matching tiles to trigger attacks, collecting characters, joining alliances — and sets them in a combat theme. According to the release there are more than 200 heroes to collect and upgrade, along with base-building, raid seasons and limited-time events.

A proven formula, and the part a launch cannot show

Jose Saarniniemi, the studio's managing director, says the game combines elements of its predecessor with a combat design and that the team expects it to build a community, with more themes and upgrades to follow. That is how a publisher describes an extension of something already selling well, and Puzzle Combat is offered as a free download rather than a paid title.

What the announcement does not say is how the game earns. Free mobile games make their money from purchases inside them, and companies rarely publish that number at launch. Nor does it say how many people are expected to keep playing after the first week, which for a match-3 title is the figure that matters: a game with hundreds of characters is asking to become a daily habit, and habits are not made on release day. Whether Puzzle Combat becomes the successor the studio hopes for, or another title in a crowded puzzle market, is a question only the months after launch will answer.