Bouhhhhh ! Infection, zombie, virus they are everywhere on the net. And I am slightly ashamed to bring that here. However, I am not enough to stop me making that suggestion :

It might be fun and allow new challenges to add a new type of creature : the "kind little pink cubes". That is, a variation those angry blue cubes brillantly called N°10 in the editor.

• Blue cubes would follow you AND the pink cubes
• Pink cubes would try to get close to you (for protection) and go away from the blue cubes
• Pink don't hurt you (actually, in terms of triggers, they are not considered as monsters)
• When a blue touches a pink (one or more times, I don't know), it turns brown for a few seconds, stops moving (or moves very slowly) and then becomes a blue cube.
• Pink and blue ignore the brown ones (don't escape, but are not attracted)
• When every monster is killed, you get a bonus for every surviving pink cubes (maybe, depending on their number, they could all gather to leave one or more powerups, or apple, or whatever)
• The player can shoot the pink cubes (would they do anything special ? Such as turning into something solid... Not sure)

Add a trigger "more than x pink cubes left", and I could see interesting challenges there...

More technical :
This would require to change a bit the behaviour of the blue cubes, as they won't only follow the player. One solution would be to consider the actors as "attractors" or "repulsor" with a different value for the blue and pink ones. The attraction and repulsion caused by an actor to another would be higher the closer (something like 1/distance, or 1/(distance²) ). They would create "vectors of attraction" (direction and strenght of the attraction caused by an actor to an other). For a given actor, every vector of attraction created by the others are added. The resulting vector would give the direction where the actor is trying to move.

So pink cubes are attracted by the player, by try to escape the blue cubes. As the result of the stated rules, we could see :

• 1 single blue arrives from one direction, a large group from another, the pink will first move toward the single one. Then as they get closer, tries to escape in another direction (or stop, depending on the configuration)
• A group of blue cubes is coming, the player is not too far. The pink close enough to the player will move behind him. If the group of blue is getting closer to the player, more pink will escape.

So, any thoughts on that ?

A question remains : could you bring your little pink friends from one screen to another ? That might be fun...