Not a lot of people talk about water bricks being a memory of good times, which is kinda disheartening. I remember fondly building a nice little water slide (yet not exactly whom it was with which is important sadly), and this was pretty much the epitome of collaboration. We would take turns deciding which brick to use. We had a choice between making the slide higher/lower, the current speed, and the direction in which to take it. I think I have a save of it but I reckon it's too old to have it anymore.
I also remember when Pandan used to do things that were things, I mean no harm but really my favorite thing of his was the babykart and the raceways. The problem though is you could never catch up when racing with others because it wasn't hard and we kept at a constant speed. It was still fun, but the best thing ever was I think an 8 person race on snails.