Concepts that Didn't Make It: DDR-DOS
DDR-DOS was a command line OS you controlled with a DDR foot pad. Eight random letters were displayed at a time. If one you wanted came up, you hit the appropriate foot pad. Music played in blazing early-80s era PC-Speaker glory.
The cocky kid at the local arcade mastered it and formatted your hard drive in 13.3 seconds. You loved that hard drive. It had your novel and your favorite family recipes and now it was gone in a puff of caffeine-fueled glory. Oh well.
You could always try MacAroni, the early Apple clone you ate when it became obsolete.