Wow. Made back in the ancient days of 1996, Roboworld is something else altogether. Designed for Beginners to anything beyond Sweeney's worlds, it captures the best of the original games and adds a futuristic flavour with excellent programming and a thorough plot. Suffering from a few syndromes of the time, invisible mazes are used a few times (including one that turns the walls back to invisible when you touch them! ?+zap!) However, the game is huge and so much greater than these small inconveniences that one can put up with ?+zap-ing through them.
Some of the most innovative parts to this game include: a reverse maze, where you must walk on fake walls and avoid invisibles; cycling of preprogrammed objects from one creature to another; a DOS prompt which attacks; Windows 3.1 for Giant Supercomputers; ZZT for Windows (just a screenshot -- sorry).