Six months after it's announcement at the Games for Health conference in Boston, Massachusetts, Six to Start, makers of gamified fitness app Zombies, Run!, has launched The Walk, a new iOS and Android app sponsored by the UK's Department of Health and NHS.

The app will cost $4.99 with an introductory price of $3.99 and is designed to take three months to play through the story, a length designed to be long enough for users to establish a habit of walking more. Unlike Zombies, Run!, which users have to actively use, The Walk uses the smartphone to passively track all day movement and incorporate that into the story, according to the company.

“We already know from Zombies, Run! that a great story can motivate people of all fitness levels to move more," Naomi Alderman, co-creator and lead writer of both Zombies, Run! and The Walk, said in a statement. "I’m particularly proud of the immersive world we’ve created in The Walk -- with engaging characters and a gripping story but also a host of maps, newspaper cuttings, audio artifacts and even a comic strip you’ll find to help you work out who did plant that bomb in Inverness station, and why. The Walk is designed to be addictive, in the best possible way. ”

Although the app takes its gamification cues from Zombies, Run!, Six to Start used the NHS funding on the technical side, developing "a special energy-efficient background motion-tracking system to monitor players’ daily walking." That's in addition to the device making use of the M7 motion co-processor in the iPhone 5s.

The game includes 65 episodes and 800 minutes of audio story. The difficulty of the game, and the number of steps needed to complete chapters, is adaptable and adjusts itself based on a learning algorithm. This is to make sure the game provides a benefit to people at any fitness level.

“Instead of focusing on your daily — or a couple of times a week — bout of exercise, this is something that will track what you’re doing throughout the day and encourage you to go a little bit further,” Alderman said this summer. “In the same way that with a great game or a great TV show you might go ‘Oh, just one more episode, just one more chapter before bed,’ we want people to be saying ‘Just one more walk around the block before I get home. I just want to hear the next bit of this.’”