So, the FlxG collide method knows how to tell which tiles in a tilemap are walls or not walls, but the overlap method does not. If you write a simple custom collision with the overlap method and tell it to .separate(), your sprite will collide with every tile in the map, not just the walls.

This is expected behavior, as there's a note in the FlxG documentation that says:

this takes the entire area of FlxTilemaps into account (including "empty" tiles). Use FlxTilemap#overlaps() if you don't want that.

On the other hand, the documentation for FlxTilemaps.overlaps() says:

Checks to see if some FlxObject overlaps this FlxObject object in world space. If the group has a LOT of things in it, it might be faster to use FlxG.overlaps().

In my scenario I have a lot of tilemaps and just one object to collide with them, the player. The way this is written, I'm thinking I have to call this method for EACH MAP, i.e. map1.overlaps(player), map2.overlaps(player), etc. Whereas with the FlxG method I can pass it the entire FlxGroup of maps as one parameter and the player as another parameter, which seems way better. I guess I could write a function with a loop that iterates through each map doing this one by one, and then call that in update(), but I'm getting the impression that it might be really inefficient.

What's the best approach here? Am I missing something obvious?