Arizona Sunshine [Review: 8.5/10] is getting an update that supports full locomotion. That part we knew, but what we didn’t know was how much money the game made so far.

Developers Vertigo Games and Jaywalkers Interactive today said their VR zombie shooter made $1.4 million in sales during its first month of release on the Oculus Rift and HTC Vive, from Dec. 6 to Jan. 5. In a prepared statement, Vertigo Games’ Managing Director, Richard Stitselaar said “from what we can tell, it may be the fastest selling non-bundled PC VR title to date.” The game usually sells for around $40 and we confirmed with Vertigo the $1.4 million figure that was shared is the amount sold before a cut taken by Valve’s Steam or Facebook’s Oculus store.

It is well-deserved; Arizone Sunshine was named UploadVR’s 2016 Game of the Year shortly after its launch. The first-person shooter uses position tracked controls to offer an intense zombie massacre in which the player treks across the Arizona desert.

Arizone Sunshine isn’t the only VR game to see success over the past year. Earlier this month we reported that Owlchemy Labs had sold $3 million with its Job Simulator since launch in April 2016. Furthermore, The Gallery developer Cloudhead Games and Raw Data developer Survios have both independently confirmed to UploadVR that they cleared $1 million in sales for their respective titles.

Along with the sales milestone, Vertigo took the opportunity to formally release the full locomotion update, arriving today. That means players will be able to navigate the game’s world using controls similar to a normal first-person shooter game, which fans had requested as an alternative to the teleportation system the title already uses.

We’re expecting the game to arrive on PlayStation VR later this year, though no final date has been set.