Reading this maze
Coral crossroads starts at row 3, column 3. Of the 42 grid positions, 34 are paintable and 8 are walls. The start is already painted; the other 33 tiles remain to be reached.
Diamonds A at row 3, column 5 and row 2, column 1 toggle the gate marked A. Diamonds B at row 2, column 4 and row 5, column 1 toggle the gate marked B. Start right and stop at row 3, column 7. Either matching diamond flips its letter; both A diamonds share A, and both B diamonds share B. The first slide covers 5 of 34 target tiles.
The verified opening crosses 4 tiles before stopping. A breadth-first search proves a 27-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.