About Number Puzzle
The 15-puzzle has driven solvers happily mad since the 1870s, when it sparked one of the first international puzzle crazes. Slide tiles in the 4×4 frame until 1-15 sit in order — in as few moves as you can.
How to Play Number Puzzle
- 1Tap any tile adjacent to the empty space to slide it (arrow keys work too).
- 2Arrange the tiles 1-15 left-to-right, top-to-bottom.
- 3Your move count is your score — lower is better.
Tips & Strategy
- ◆Solve the top row first, then the left column, and never disturb them again.
- ◆Learn the 3-tile rotation: cycling three tiles around the blank is the atomic move of every solution.
- ◆The last two rows solve together, column by column, not row by row.
Frequently Asked Questions
Is every shuffle solvable?
Yes — we check the mathematical parity of every shuffle, so the unsolvable arrangements that fooled 19th-century players never appear here.
What is a good move count?
Under 120 moves is solid, under 80 is excellent; the theoretical optimum for hard positions is 80 moves.
Why is it called the 15-puzzle?
Fifteen numbered tiles plus one gap in a 4×4 frame — the gap is the sixteenth square and the whole trick.