Notes on this puzzle
This expert slider scatters 24 tiles across a 5×5 tray, with the gap in row 2, column 4. Not a single tile starts in its home square.
Add up how far each tile is from its home square and you get 90, so no solution can be shorter than 90 moves. Solving it row by row, the method from our guide, takes 216 moves on this board. Tile 19 has the longest trip home: 6 squares.
Where to beginOn 5×5, peel off the top row and left column twice; only then does the board become a familiar 3×3.