I remember when I was in grad school, there was this website with a cool interactive game, where you were given certain "rules" (like 'abac=1'), and then you had to reduce a given word to the identity using those rules. I remember it kept track of how many moves you made, and told you if you did it in the optimal number of moves or not. I don't remember if it explicitly said you were doing group theory or not. I remember the NY Group Theory Seminar page had a link to it, but that site seems to be dead now.
Anyone know what I'm talking about / have a link?