Try to pass through a labyrinth - or let the program find the way...
This puzzle should work in all newer Squeak images (the oldest I tried was 3.2gamma), though it is necessary to file in the Matrix class to versions prior to 3.7, and to hide the WorldMainDockingBar in versions newer than 3.8a-5976.
(I finally figured out how to break the run of massive sequence of graphical operations which called for a quick update of Labyrinth to version 3.)