The title was first unveiled on stage in 2017 during Apple's headline iPhone X event. Originally it was billed as an Apple TV-only game that would support single-finger play using the Siri Remote, but the developers have since focused on getting the game out for iPhone and iPad users first.
According to the Sky website, the game's "coming soon" to Android, Mac, Apple TV, PC, and consoles. Sky was originally supposed to come out for iOS on July 11 but last-minute issues caused a weeklong delay.
Sky: Children of the Light is free to download on the App Store [direct link], and offers a variety of in-app purchases starting at $0.99.