This is an implementation of the Mastermind game in Eiffel.
It supports an arbitrary number of colours and pins, and can be played by both humans and computers (the computer's "AI" is alright; it uses an algorithm that's faster than Knuth's, but not as good).
It was originally for a college assignment, but I thought I'd stick it as something that people learning Eiffel could look at; I found very little Eiffel code on the net when I was learning it.