One of the games we play at the robotics workshop is the farming-on-mars game. The robots drive about, always keeping within a field thanks to their line sensors. The children have to design a scooping device to attach to their robot so that it can sweep up as many potatoes (sweets) as possible in 1 minute, anything it sweeps out of the field (black tape in the picture below) is theirs.
Sweets are pretty light so the best strategy is something like this
A variation of this game is to make the potatoes heavier. If the scoop is too big the robot will catch too many in one go and get stuck.
This isn't a super complex game but it introduces loads of stuff to think about, the idea of trade-offs in engineering, suitable materials. Also the design of the scoops has many variables aside from width: Should they touch the floor to catch the small objects? what about friction? How do you attach the scoop to the buggy? Be careful not to obscure the line sensors!
It gets harder though! When the buggy gets to the edge of the field it will stop and turn around; the rules say you get to keep anything it pushes out. How should you program the robot so that it doesn't drag its catch back into the field?
That's why we love these games at Inspired Minds, they're all about conceptually simple games with many solutions. They encourage teamwork, creativity, improvisation and of course, they're fun.