Indie developers often struggle to get the attention they deserve on the App Store, and Shelly Alon is no exception. While we loved Alon’s 2014 people puzzle Partyrs, the game failed to shoot to the top of the charts the way we thought it should. His second  mobile game, Sputnik Eyes, took a totally different approach to puzzling in 2015 — and if you didn’t pick it up when it launched, you can do so right now without spending a dime.

The objective of the game is devilishly simple; players just need to get the aliens on the corners that match their color. Being a puzzle game, of course, things are a wee bit harder than that in practice. Aliens can only move along pre-determined paths, and there are other little wrenches thrown into the works as well. Scoring is based not just on level completion, but on how quickly you were able to solve it and in how few steps.

If you’re a fan of puzzle games, Sputnik Eyes would be an easy recommendation at any price. Be sure to grab it now while it’s free (and if you love it, show the developer some financial gratitude and pick up Partyrs).