Reading this maze
First stripe starts at row 1, column 1. Of the 5 grid positions, 5 are paintable and 0 are walls. The start is already painted; the other 4 tiles remain to be reached.
Slide right to the boundary. All five floor tiles lie on this one straight row, so one complete slide paints the board.
The verified opening crosses 4 tiles before stopping. A breadth-first search proves a 1-slide finish from this exact starting board; that is a reference target, not a move limit. You may revisit any painted tile.