When I was in Primary School, in the term of the year they had activities afternoons when parents came in shared hobbies with you. One of these activities was computers, now this was back in the days of BBC micros, C64 and Spectrums, but one of the kid's mum was real geek and had an early mac with a basic platform game, which was completely addictive. Not for the game play but because it allowed you to create your own levels.
I didn't think I'd ever find a game with this simple joy and then my brother stuck Little Big Planet on I was transported back to that childish creative joy. I knocked this Moai head up out of cardboard after only 20 minutes of playing, I could kill so much time building levels for this game.