You’ve probably heard of Monument Valley even if you’ve never played it. The popular indie mobile game was named one of Apple’s games of the year in 2014. It usually costs a few bucks to download, but you can grab it right now for free in the iOS App Store.

Monument Valley is hard to describe, but I’ve heard it referred to as puzzle game set in an M. C. Escher painting. The original game, released in April 2014, included ten mind-bending levels. The company also added an eight-level expansion called Forgotten Shores in November 2014, though you’ll have to pay an extra $1.99 to try it.

More recently, the same company developed a virtual reality game called Land’s End specifically for the Gear VR. It’s possible this new promotion could be an effort to grow its fan base as the developers continue to expand beyond traditional mobile gaming.

Monument Valley still costs $3.99 if you want to play it on Android or on a Windows device. It’s also unclear how long this offer will last for iOS so, if you’re interested, you might as well download it now.