Click a tile adjacent to the empty space to slide it in. The goal is to arrange all numbers in order from left to right, top to bottom. You can also use arrow keys.
3×3 (8 tiles) is great for beginners, 4×4 (15 tiles) is the classic challenge, and 5×5 (24 tiles) is extremely difficult. Complexity grows exponentially with size.
Solve the first row first, then work row by row. The last two rows need to be solved together. Follow the 'corners first, edges next' principle to avoid disturbing solved tiles.
