Reading this maze
Parallel circuits starts at row 6, column 5. Of the 42 grid positions, 33 are paintable and 9 are walls. The start is already painted; the other 32 tiles remain to be reached.
Diamond A at row 6, column 7 toggles the gate marked A. Diamond B at row 4, column 2 toggles the gate marked B. Start up and stop at row 4, column 5. A and B keep independent states; a diamond only changes its matching letter. The first slide covers 3 of 33 target tiles.
The verified opening crosses 2 tiles before stopping. A breadth-first search proves a 24-slide finish from this exact starting board; that is a reference target, not a move limit. You may revisit any painted tile.
Diamonds A and B control separate gate groups. Each letter toggles only its matching barred gate; the other group keeps its current state. Changes take effect during the same slide. Undo restores both groups, and Hint searches from both gate states and the painted floor.