[Kristine1975]

>Journey where the only possible interactions between players are positive or helpful.

There was a GDC presentation a few years back where the lead designer Jenova Chen talked about how difficult it was to make only positive/helpful interactions possible. In playtesting even the ability to collide with another player was used against them, e.g. to push them off a cliff.

The presentation should still be online for free at http://gdcvault.com very interesting from a game-designing point of view.