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?


The game's name is ExpaCon and was developed by Prof. Gilbert Baumslag. It is mentioned in this blog.

You can apparently download an Android app - see here.

Edit: Robert W. Bell's cv reads

Developer and consultant for Expacon - a mathematical game based on group theory by Gilbert Baumslag

So in last resort you could try contacting him.

  • $\begingroup$ Yes, expacon! Seems it is completely gone though :( $\endgroup$ – Steve D Apr 27 '18 at 21:44
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    $\begingroup$ @SteveD There may still be hope - see edit. $\endgroup$ – Arnaud Mortier Apr 27 '18 at 21:52
  • $\begingroup$ Ooh, the plot thickens - I'll shoot him an email, see what happens. $\endgroup$ – Steve D Apr 27 '18 at 21:59
  • $\begingroup$ Unfortunately Gilbert Baumslag died in 2014. $\endgroup$ – Derek Holt Apr 28 '18 at 21:34
  • $\begingroup$ @DerekHolt Yes, this is why I removed the unfortunate suggestion to contact him as well. $\endgroup$ – Arnaud Mortier Apr 28 '18 at 21:35

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