About Sliding Puzzle
Sliding Puzzle presents a grid of numbered tiles with one empty space; your task is to slide tiles into the gap until they are arranged in numerical order from left to right, top to bottom. The classic version uses a 4×4 grid of 15 tiles (known as the Fifteen Puzzle), but this game offers 3×3 (8 tiles), 4×4 (15 tiles), and 5×5 (24 tiles) modes. Difficulty scales non-linearly: the 5×5 grid has roughly 10 quadrillion possible states, making random scrambles far harder to untangle without a systematic method.
Every randomly generated board is guaranteed solvable — the game checks parity before presenting a scramble. An unsolvable board (odd-parity permutations on an even-width grid) would have no solution regardless of move count, so this check is essential for fair gameplay. Move count and elapsed time are displayed throughout, and your personal best for each grid size is saved locally so you can track improvement over multiple sessions.
The world record for the 15-Puzzle (4×4) is 20 moves — known as God's number for this configuration. In practice, expert human solvers average 50–80 moves on a random scramble using the row-by-row technique. At 5×5, optimal solutions often exceed 200 moves, and even experienced solvers take several minutes on difficult scrambles. The gap between "can solve it eventually" and "can solve it efficiently" is what keeps the Sliding Puzzle engaging across thousands of attempts.
How to Play
- Click or tap an adjacent tile — Slides it into the empty space
- Arrow keys — Slide tiles in the indicated direction
- New Game button — Generates a fresh random solvable scramble
- Grid size selector — Switch between 3×3, 4×4, and 5×5 before starting
- Move counter and timer start on your first move
- Your best move count and time are saved for each grid size separately
Tips & Strategies
Solve row by row
Complete the top row first, then the second row. Once two rows are locked in, solve the remaining section column by column. Never move tiles that are already in their correct row.
The last-row exception
The bottom two tiles in each column cannot be placed directly — use a rotating cycle of 3 moves to position them without disturbing rows above. This exception catches most beginners.
Count your blank-space moves
Every solution passes through the empty space. Think of moving the blank, not the tiles — planning the blank's path is easier than visualising tile trajectories.