Sliding Number Puzzle

The sliding number puzzle is a tray of numbered tiles with one empty space. Slide tiles into the gap until they are in order, reading left to right and top to bottom, with the gap in the bottom-right corner.

Game Oix shuffles every board using legal moves from the solved position, so every puzzle can be solved. Choose 3×3 (Easy), the classic 4×4 "15 puzzle" (Medium), 5×5 (Hard) or 6×6 (Expert).

1. Tap a tile next to the empty space to slide it.
2. You can also tap any tile in the same row or column as the gap to slide the whole line at once.
3. The arrow keys slide a tile into the gap from that direction.
4. Tiles in their correct position change colour.
5. Finish with all tiles in order and the gap in the bottom-right corner.

• Solve row by row, starting with the top row; never disturb a finished row.
• For the last two tiles of a row, park the last tile one space early with its partner beneath, then rotate both in together.
• Solve the last two rows column by column, using the same pairing trick.
• Keep the gap in the unsolved area.

Step-by-step guide: A Beginner's Guide to Sliding Number Puzzles.