I build a rough prototype with Unreal engine.

 

 

Childs will get 30 oranges

Then they can decide to give it for themself or to give it for helping others

If they give it to others, they will get 2-10 oranges randomly during the time remaining and feel fulfilled of helping others with getting  more happiness points

Then they try  to get the most oranges and the happiness

Finally they will found that giving all their oranges to help others is the best solution