I spent a good deal of time looking at the graphics roms used in Pac-Man, well actually, I was looking through the source code to MAME to see how it loaded in the roms. I then started designing an application to work with it. It was going to be a hex/binary editor, graphics editor, and maze editor.
It was originally a Watcom/ZSVGA program, and not much coding was done on it at all before I found Ivan Mackintosh's "AGE" project. I then decided to focus my efforts on AGE, which at the time only loaded in Centipede graphics. I collaborated with him for a few years, adding in all sorts of utility to his project.