The pathing tries to find the best route possible.
In open areas there's lots of identical paths for it to take;
To choose which path it will go it follows these priorities:
UP, RIGHT, DOWN, LEFT.
This means that the path will go UP as far as it can first – then right, down, left.
If the path is going to the TOP RIGHT from the BOTTOM LEFT, the path will go UP all the way to the top, then RIGHT.
If the path is going to the BOTTOM LEFT, from the TOP RIGHT, the path will go all the way DOWN and then LEFT.
TOP LEFT, from BOTTOM RIGHT, UP, then LEFT.
So, BOTTOM LEFT, from TOP RIGHT? If you answer "DOWN then LEFT" you are correct!
If you answered "uhhmm.. what's up with the directions in caps?" then you get a bonus point!
Remember, teleports are traps and do not effect the path choice.
The Green start location on a map starts the Green Path, or 'Path 1'.
The Green Path noted by the green in the arrow may pass over Green Allow blocks:
The pathing is very greedy. It's only looking at it's next target.
It does not look at the big-picture. You can use this to your advantage.
When there's more than one checkpoint, you can completely wall one off.
Not many maps will contain more than one of any checkpoint.
The below demo demonstrates it's greed. - The path will actually be shorter if you wall the bottom A!