I started going through those somewhat recently and have really enjoyed it. Thanks for putting that together.
For anyone else looking for another one along the same lines, this is a good one too: http://overthewire.org/wargames/natas/natas0.html
http://cryptopals.com/
Set #1 starts out with a simpler problem than Pigpen, and then a problem that's just barely harder than Pigpen, but that requires actual code and whose solution will also help you break repeated-nonce AES-CTR.