a mechanical engineer instructor used to test his class with problems..

once he put a ping-pong ball inside a vertical pipe barely large enough to fit in and cemented the base so it couldn't be moved...then told the kids they had the entire resources of the shop to get the ball out without breaking it.

There were elaborate plans for vacuums and sticks with glue and thin strips of metal....until one kids got a look in his eye, and filled a canister with water, poured it in, and floated the ball out in 10 seconds.

Amos..(and others)...have you ever played the card game "New Eleusis"? Some friends & I used to play about 20 years ago. It requires some 'interesting' thinking, both in strategy during play, but also in setting up each 'game' so it can be played without being too easy or too hard.

We found some people were psychologically resistant to coping with the rules, and got very frustrated.