Notes on this puzzle
This hard slider scatters 15 tiles across a 4×4 tray, with the gap in row 3, 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 42. 1 pair of tiles already sit in their correct line but in the wrong order, which pushes the minimum to at least 44 moves. Solving it row by row, the method from our guide, takes 102 moves on this board. Tile 4 has the longest trip home: 6 squares.
Where to beginSolve the top row, then the left column, and treat what remains as a 3×3 puzzle.