vttom - that is a great t-shirt. Sounds like it was too easy for the teenage boys. How about doing it in hex?
funny you mention hex, when i was at school we used to graffiti messages in hex to fellow students who understood what is was on the toilet walls and school desks... until the teachers started decifering it, after the computer studies teacher worked out it was hex (took him a while), and eventaully we got caught out by the maths teacher, who we paid back the detention she gave us by re writing a weeks worth of maths homework questions and answers in hex ... she loved that...
we even converted answers during class and yelled them out in hex just to add to it,
