Taco Bell has quietly rolled out a loyalty game that will get a bigger push starting Wednesday as the fast-food chain tries new ways to connect with its biggest fans.

The game, Explore, sits within the Taco Bell app, which has already been downloaded more than 4.7 million times since its October 2014 launch. Explore rewards users for typical restaurant usage such as orders through the app. In a twist from conventional loyalty programs, it also rewards users for sharing various "Live Mas" experiences on Facebook, Twitter and Instagram, even for events that have nothing to do with Taco Bell.

"We're not rewarding people for talking about Taco Bell, tweeting Taco Bell (or) using #livemas. We are actually just rewarding people for living their lives," said Tressie Lieberman, Taco Bell's VP-Digital Innovation and On Demand. She calls Explore a game, "not a loyalty program."

Users who share photos and details on the various social sharing sites can unlock pieces of puzzles, as do those who order using the app. Users who complete the first puzzle get a free Freeze drink, while those who complete additional puzzles can get rewards such as gift cards worth up to $100, a reserved booth at a Taco Bell restaurant, or a trip to Taco Bell's California headquarters.

Users can see where they place on a leaderboard, one that lists leaders overall and friends who are also playing the game. While the reasons behind the reward system may seem unclear to users, Ms. Lieberman said there's a real algorithm behind it.

Taco Bell has seen a "phenomenal response" to its app since it launched on Oct. 28, 2014, said Ms. Lieberman. "We're really starting to see a lot of traction with people placing mobile orders." Last week, CEO Brian Niccol told analysts at Yum Brands' investor day that Taco Bell is seeing 20% check increases from people using mobile app.

While she declined to share details on usage of the app overall, more than 60,000 people had already used Explore before it was promoted, and 30% to 40% of them are letting Taco Bell access their social networks, Mr. Niccol said at the Dec. 10 meeting. Starting Wednesday, Taco Bell plans to promote the game via channels such as Facebook, Instagram, a Snapchat story and its own Taco Bell site.

"They are coming back into app more than ever before," Ms. Lieberman said.

The first season of Explore is set to end in May and season two will likely offer users a different experience, Ms. Lieberman said.

DigitasLBi designed the app and the Explore program, Kiip worked on the reward delivery and Cardfree worked on app development and integrating Explore into the app, she said.