Reading this maze
Two signals return starts at row 3, column 3. 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.
Diamonds A at row 2, column 3 and row 3, column 6 toggle the gate marked A. Diamond B at row 4, column 6 toggles the gate marked B. Start left and stop at row 3, column 2. Either A diamond flips A; the B diamond changes only B. Revisit the shared signal to adjust a later crossing. The first slide covers 2 of 33 target tiles.
The verified opening crosses 1 tiles before stopping. A breadth-first search proves a 22-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.