Sliding Puzzle (15-Puzzle)

How to play

Click any tile adjacent to the empty space to slide it into the empty spot. Arrange all tiles in order from 1 to 15, reading left to right and top to bottom. Solve it in the fewest moves possible!

Why the 15-Puzzle Stood the Test of Time

The 15-Puzzle was invented around 1878 and became a worldwide craze almost immediately — Sam Loyd, the famous American puzzle designer, famously offered $1,000 (worth roughly $30,000 today) to anyone who could solve a specific starting configuration, knowing it was mathematically impossible. That unsolvable variant is what made the puzzle famous: roughly half of all random scrambles are unsolvable, which is why this version scrambles by applying 200 random valid moves from the solved state rather than randomizing the tiles directly. The result is a guaranteed-solvable board every time — and a puzzle that's easy to understand but surprisingly hard to solve efficiently.

Key Features

• Always solvable scramble: The board is scrambled by making 200 random legal moves from the solved state — guaranteeing solvability in a way that pure random tile placement cannot.
• Green correct-position feedback: Tiles that are already in their correct position display in green — gives you a quick visual progress indicator without needing to mentally verify each tile's target position.
• Move and time counter: Both moves taken and elapsed time are tracked simultaneously — you can optimize for fewest moves, fastest solve, or both.
• Persistent best-moves record: Your lowest move count across all sessions is saved in localStorage — the key metric for measuring improvement in puzzle-solving technique.
• Touch-optimized: Tap any tile adjacent to the empty space on mobile — the same interaction as desktop clicking, fully responsive down to small screens.
• Instant new puzzle: Generate a fresh scramble anytime with one button — no page reload, timer resets, and you're straight back into it.

Real-Life Use Cases

• Spatial reasoning training: The 15-Puzzle requires holding the current board state and multiple future moves in working memory simultaneously — a demanding spatial cognition exercise.
• Patience and persistence practice: Unlike fast-reflex games, the 15-Puzzle rewards deliberate thinking. It's a good choice for people who want a challenge that rewards calmness over speed.
• Mathematics education: The puzzle has rich connections to group theory and permutation parity — teachers use it to introduce these concepts tangibly before the abstract math.
• Travel entertainment: Classic puzzles like this load instantly and work offline once cached — ideal for situations where you want a mental challenge without a data connection.

Who Can Use This

Anyone who can count to 15 can play — the rules are as simple as a puzzle gets. The challenge is in execution, not comprehension. Younger children will enjoy the tactile satisfaction of sliding tiles; older players and puzzle enthusiasts will work on reducing their move counts. It's particularly satisfying for methodical thinkers who prefer logical deduction over reflexes.

Tips & Best Practices

• Solve row by row, top to bottom: The standard efficient approach is to solve rows 1, 2, then columns in row 3, then the bottom 2×4 section. Don't try to solve the whole board at once.
• Place tiles 1 and 2 last for row 1: Placing tiles 1 and 2 in a completed row requires temporarily rotating them into position from below — there's a specific 3-step rotation pattern worth learning.
• The last two rows require special techniques: The final 2 rows (tiles 9–15) can't be solved using simple row-by-row logic. You need the "3-cycle" technique: rotate three tiles in a loop while keeping others fixed.
• Think 2 moves ahead, not 1: Every move shifts the empty space. Plan which direction the empty space needs to travel to be adjacent to your target tile — it's the empty space you're really controlling, not the tiles.
• Use the green indicators: Keep checking which tiles are already correctly placed. Preserve those positions as you solve other areas — accidentally moving a correctly placed tile costs you extra moves.