I couldn't really find a forum in which this problem could fit so I try to post it here. I have to prepare a science based (physics, math, chemistry) game/competition for children aged 9-13. It should be about some funny and exciting experiments, solving various problems in mentioned fields. The problem is I'm out of ideas. I was thinking about doing something with ciphers and cryptography, maybe to make some simple steam engine for a boat and then race, ... something like that,... Does anybody have a good idea for this kind of games? Internet resources would be also helpful. Thanks a lot.