Okay, I mostly got the movement stuff sorted out. i'm having some oddity in entities moving slowly or quickly towards a location, I think that might have to do with mixing fixed/relative/location attributes. I have this idea for a train boss that moves on a couple of different fixed paths with him "entering an exit" at the edge of the screen and then teleporting to a different "entrance" using the locations. It is having teleport issues. However, since there is a demand for low level enemies I've been workgin on those instead. Interestingly using fixed locations can move your entity outside of the map boundaries, which has some potential (and potential for trouble). If you want to keep entities inside the boundaries, relative movement using angle and speed seems to be the way to go.
My current problem is in regards to using the bullet attribute follows_previously_spawned_entity. The wiki entry:
follows_previously_spawned_entity (bool)
*makes this entity follow the last entity spawned by this operation
*for now [b]only[/b] works with a pattern triggered by an entity's [u]spawning_patterns[/u] attribute
*also, only takes effect on an entity after the spawning bullet behavior has concluded (without a die tag); before that point the bullet pattern itself decides where it moves
entity attribute spawning_patterns
spawning_patterns (List<bullet_pattern>)
when this entity is spawned by room-generation, instead of just spawning one at the center of the corresponding tile, it picks one of the bullet patterns in this list, then spawns one entity per bullet node that's a direct child of the pattern (so child nodes that do their own spawns don't count)
What I think I figured out at this point in writing this is that it works like this:
An Entity Y with spawning_pattern X spawns in a room. Entity Y then spawns new entities around it in the pattern specified by spawning_pattern X. Those entities then move according spawning_pattern X.
Which is great, except it is nothing that I was interested in using. I wanted to get bullets to follow bullets, but wait, shots are entities. But bullets aren't shots. So never mind again.
And now if anyone else has this bright idea they can save themselves some trouble, unless I'm completely wrong.