YouTuber Apple Demo has found a prototype third-generation iPod that contains a game called Stacker, which never made it to retail models. In addition to Apple’s own version of Tetris, the engineering sample iPod also came loaded with other unreleased titles, including games called Block0 and Klondike, as noted by Engadget.

On the back of the prototype iPod, a “DVT” (Design Validation Testing) label is etched where the storage capacity normally goes, which, Apple Demo explains indicates it was from the middle stage of development. Two songs still in its storage and a helpfully-named playlist suggest this device was used for battery testing.

After some tinkering and transplanting the internal hard disk into a second-generation iPod Apple Demo got the hard disk to boot as normal, and out of the games available, they only demoed Stacker.

They even contacted the ex-SVP of Apple’s iPod division, Tony Fadell, to learn why the Tetris clone was never released. However, Fadell’s only comment, from 2022, says, “because we added games with later software release,” leaving the internal story of Stacker a mystery for now. Apple did release a licensed Tetris game years later on the “Classic” iPod models, which supported new game titles purchased from the iTunes Store.

Stacker uses the iPod’s click wheel to move falling blocks left and right, and the center button drops them to the bottom of the screen. The objective, like Tetris, is to shoot for a high score by completing and clearing lines of bricks and not overstacking pieces off the top. The game isn’t entirely polished — there’s at least one bug shown in the video where a brick overlapped a stack and got stuck when rotated. But it works!