Notes on this puzzle
This expert slider scatters 24 tiles across a 5×5 tray, with the gap in row 2, column 4. 2 tiles start in their home squares.
Add up how far each tile is from its home square and you get 78. 3 pairs of tiles already sit in their correct line but in the wrong order, which pushes the minimum to at least 84 moves. Solving it row by row, the method from our guide, takes 184 moves on this board. Tile 21 has the longest trip home: 7 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.