Implement pathfinding

[rosshadden]

Pathfinding should probably either be a mixin or a utility. Or perhaps a mixin that uses a utility? :bowtie: :godmode:

I have some great ideas for pathfinding. Just so I don't forget:

Entities with pathfinding should have a target (perhaps a selector, outlined in #16), an awareness radius, and a field of view (angle). If a target is within the awareness radius and inside the FOV, we trigger whatever pathfinding algorithm that entity possesses.

Here are some algorithms I thought up:

• One simple algorithm could be to just move toward the (closest) target.
  • This would mean they would get stuck behind objects and scenery they collide with, which is what happens in a lot of Zelda games.
• A more powerful algorithm would be:
  1. If an enemy sees a target, it "memorizes" the position they saw it at
  2. It uses whatever specific pathfinding algorithm it has been assigned to make it's way closer to that spot, like A*.
  3. Repeat steps 1 and 2. This means that even if a target moves outside the awereness radius / FOV, the chasing entity still tries to get to the last spot it remembered, and updates the memorized position if it sees a target again along the way.

Maybe the second one does everything the first does, and we just make it support different cases, and make the specific algorithm it uses for pathfinding just be the direct path. Actually I like that. So maybe in addition to an awarenessRadius, there's also a chaseOrForgetRadius, where an entity stops chasing the target if it gets outside this radius. Then the classic dumb Zelda enemy is supported, as we can make their awarenessRadius === chaseOrForgetRadius, and the pathfinding algorithm that they would use in the second step of the above explanation would be to move in a direct line toward the target. And other entities could use different chasing algorithms, like A*.

[rosshadden]

We should talk about this before either of us implements it, @oppenlander. What I have here is very rough. But I do think we can come up with a powerful set of rules that handles every case we can think of at the time. And based on the above, I actually don't think it will be that difficult!