From here:
"There are several buggy versions of this game floating around. On one version level 23 is impossible. You have a broken one, if on level 23 the initially lit lightbulb on the right is on the right edge. The correct version has this bulb three squares from the edge."
A...
Here's my contribution to the Level 23 Enigma. If someone can just figure out where to swap a mirror for a refractor, it would work. It is beyond my primitive caveman mind, however.