You might never recognized it but the wall structures in Ram Raid and Atlantis: The Last Resort hold a little secret. The textures had to be optimized a lot to run smoothly on CD-i. One of the software tricks was to mirror the textures halfway, so the bottom half is always mirrored by the top half and vice versa. This means the data stream was cut in half, as the other half was just copied. A game like Wolfenstein 3D doesn't use this trick and they designed fully designed wall textures from floor to roof. This appeared to be one of the reasons why Wolfenstein 3D wouldn't run on CD-i. Paul Clarke comments: "Both RamRaid and Atlantis had to mirror the wall textures top to bottom around the mid-point so Wolf3D (as much as I would have loved it) would never have been possible without smarter people than me as Wolf3D has distinctive full-height wall murals."
[Thanks, Paul Clarke]