How to Beat the 15-Puzzle: A Step-by-Step Method
The 15-puzzle looks hard, but it solves cleanly if you work one row or column at a time. Here is a method you can repeat on any board, including the 3×3 version in our Sliding Puzzle.
Step 1 — Solve the top row
Move 1 into the top-left corner. Then slide 2 and 3 into place beside it. Keep the empty space below the row you are building so you can rotate tiles into position.
Step 2 — Solve the left column
With the top row done, place 4 (and 5 on a 4×4) down the left edge the same way.
Step 3 — Repeat for the next band
Treat the remaining area as a smaller puzzle and repeat: top row, then left column, until only a 2×2 or 3×2 block is left.
Step 4 — Finish the last block
The final corner tiles usually fall into place with a small rotation of the remaining squares. If one tile is stuck, rotate the whole unsolved block around the empty space until it lines up.
Tip
Never break a completed row to chase a single tile. Build from the outside in and the board resolves itself. Practice a few 3×3 rounds first — they are quick to finish and teach the pattern fast.