The other day there was some discussion of a 4-dimensional game in an IRC channel I frequent. This immediately led me to think of 54321, a collection of 5 games in 4, 3 or 2 dimensions for 1 player – it’s the first four-dimensional spatial game I played. So I looked it up again, and found no hint of its existence on the author’s site (apparently now Mac-dedicated). I’d expect at least a mention of why it was taken down, but the page is simply removed. The source is still available in various places (my own copy), though, and still works today. It requires SDL and SDL_Image.