Of all the ways to chill while commuting, Monument Valley is one of the most chill — and now it's one of the cheapest, too. Ustwo's Escher-inspired puzzle-adventure has just gone free on iPhone and iPad for the first time, so even more people can get sucked into its beautiful, mind-bending world.

There's no mention of a sale in the app's description, so it's unclear how long Monument Valley will remain free; Ustwo may be banking on a critical mass of people getting hooked and forking out for the $1.99 "Forgotten Shores" expansion. The game usually sells for $3.99, and has also been available for free on Android through Amazon Underground for a while.