[Koahku]

>I also made a short (and now defunct, though I can rehost it) web-based puzzle for people on /g/ to learn a bit about encryption. Starting with a simple ROT13 and working up to audio stenography.

Durrcada? If so, I found it very fun even though my attention span is too short for that sort of things.

[Nadya]

Lain. It was a few years ago and only 6-7 steps long because I hit the threshold for my expertise (read: next to none) at the time.