Apple II Raycasting Demo
See on the USENET:
David Schmenk has written a raycasting demo - think Wolfenstein 3D - done on the Apple II using low-rez graphics. Seems to run at over 20Hz. Works great in an emulator. Awesomeness!
Rich, a frequent contributor to the comp.sys.apple2 newsgroups, has already written a level and texture editor: http://rich12345.tripod.com/loresthreed/index.html