This is the code for the memory game booklet that is available on http://books.pharo.org and whose source is available on http://github.com/booklet.
To make the demo easier to follow and help you if you get lost, we already made a full implementation of the game. You can load it using the following code:
Metacello new
baseline: 'BlocMemoryTutorial';
repository: 'github://pharo-graphics/Bloc-Memory-Tutorial/src';
load