Reading this maze
Branching diamonds starts at row 4, column 3. Of the 42 grid positions, 27 are paintable and 15 are walls. The start is already painted; the other 26 tiles remain to be reached.
Diamond A at row 1, column 3 toggles gate A; diamond B at row 5, column 2 changes only B. Start left and stop at row 4, column 1. Use closed gates as stopping points on the return crossings; A and B keep separate states. The first slide covers 3 of 27 target tiles.
The verified opening crosses 2 tiles before stopping. A breadth-first search proves a 23-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.