Notes on this puzzle
This medium slider scatters 15 tiles across a 4×4 tray, with the gap in row 4, column 3. 1 tile starts in its home square.
Add up how far each tile is from its home square and you get 23, so no solution can be shorter than 23 moves. The shortest possible solution is exactly 23 moves. Matching it is a real achievement. Solving it row by row, the method from our guide, takes 63 moves on this board. Tile 12 has the longest trip home: 3 squares.
Where to beginTiles are not far from home after this short shuffle; fix one corner, then grow outwards from it.