A ghostly, green, electronically generated hand extends outward from Nightgate’s app icon, reaching from the darkness. Is this disembodied appendage inviting you in, clawing for your capture, or begging for your help?

If Nightgate’s price tag has so far prevented you from resolving the mystery its icon presents, now is the time to give in to curiosity, as Apple has chosen it as its Free App of the Week.

Games and apps that are universal across iOS (iPhone and iPad) and tvOS (Apple TV) mean that downloading any of the three versions grants access to all of them. I would recommend playing Nightgate on as big a screen as you have access to, through either a nice sound system or headphones. The sights and sounds are what make Nightgate worth playing.

This morning I took the free bait Apple offered, and I’m glad I did.