Notes on this puzzle
This hard slider scatters 15 tiles across a 4×4 tray, with the gap in row 2, column 1. Not a single tile starts in its home square.
Add up how far each tile is from its home square and you get 35, so no solution can be shorter than 35 moves. Solving it row by row, the method from our guide, takes 95 moves on this board. Tile 13 has the longest trip home: 4 squares.
Where to beginSolve the top row, then the left column, and treat what remains as a 3×3 puzzle.