Encoding tiles symmetry and rotation
The base implementation notes that you can "Augment pattern data with rotations and reflections." I don't think you need reflections for the circuit problem but you might run into it with more complex setup.
Let's assume you don't need reflections. For rotations you need to have 4 letters that indicate the orientation of the piece.
For this issue let's call them :
- S -> straight
- L -> rotated 90° to the left
- F -> "flipped" but really it's rotated 180°
- R -> rotated 90° to the right
So this tile :

would have edges 4S, 2, 4S, 0
And this one :

would have : 4S, 1, 1, 4R
Now the complicated bit is that you have to account for that whenever you are rotating a piece. For a Left (90°) rotation :
- every S becomes L
- every L becomes F
- every F becomes R
- every R becomes S
This also fixes the problem of having 5.png left edge connecting to a 4S the wrong way because it will never be a 4S AND a top facing edge at the same time.