The studio Swarm Behavior gathers simulations and games related to swarm behavior, multi-agent systems, clone interactions, self-organizing systems, artificial life, etc:

http://scratch.mit.edu/studios/215351/

So, in general, the projects in there define multiple agents that interact with each other.

With the introduction of clones in Scratch 2.0, the implementation of swarm behavior with a variable number became easier. However, the implementation of interaction with, e.g. the nearest clone is still difficult, therefore the studio should be also a source for programmers to get ideas how to implement distributed systems.

Currently, most projects are demonstrations or simulations where you can set parameters - we are still short on games.

You are invited to come by, watch, love and favorize ;-)

Wow. All these projects are fascinating. I was working on something that might fit in here. I'll have to revisit it.