Sliding block puzzle online

How to play

1. Spot the big block and the exit. Every level has one red 2×2 block and a green Exit tab on the wooden frame. The exit can be on the bottom or the right side, so look before you move.
2. Slide blocks into empty squares. Drag a block with a finger or mouse. It slides along the grid, may turn a corner in the same drag, and stops when something is in the way. Blocks never rotate or jump.
3. Use tap controls if you prefer. Tap a block, then an arrow button, or tap an empty square it can reach. Arrow keys work on a keyboard.
4. Free the big block. The level is solved when the red block reaches the exit opening. Fewer moves is better: moving the same block again straight away is still one move.
5. Undo, reset, hint. Undo steps back, Reset starts the level again, and Hint plays the next move of a shortest solution from where you are.

Kinds of sliding puzzles

“Sliding puzzle” covers a few different games. Knowing which one you are playing changes how you think:

• Exit puzzles (this page): blocks of different sizes, one target block, one exit. The challenge is making room. The best-known 4×5 version is klotski, called 华容道 in Chinese.
• Number sliding puzzles: equal square tiles with numbers, such as the 15 puzzle, where the goal is to put them in order. That is a sorting problem rather than a traffic problem.
• Picture sliding puzzles: the same idea as numbers, but the tiles form an image.
• Packing puzzles are not sliding puzzles at all: you lift pieces and fit them into a box, as in our wooden block packing puzzle.

Beginner techniques for sliding block puzzles

• Plan the big block’s route first. Trace the path it must take to the exit, then list the blocks sitting on that path.
• Create parking spots. Before you move a blocker, make sure there is an empty space it can go to, ideally in a corner away from the route.
• Move small blocks in pairs. Two 1×1 blocks side by side behave like one 2×1 block, which can open a lane for a long block.
• Look for ‘trains’. Often several blocks need to shuffle in a loop, each moving into the space the previous one left. Repeat the loop until the gap is where you want it.
• Watch the exit side. On side-exit boards the big block must line up with the opening, so its row matters more than its column.
• Undo is free. If a position looks worse than three moves ago, go back rather than pushing on.

What makes a sliding puzzle hard?

Our search reports two numbers for each level: the fewest moves, and how many different positions can be reached at all. You might expect a bigger position space to mean a harder puzzle, but the two are only loosely linked. Level 4 has the largest space here (81,462 positions) and needs 11 moves, while level 6 can reach only 260 positions yet needs 17.

What really makes a level hard is a narrow bottleneck: a stretch where only one or two moves make progress and everything else just shuffles blocks around. Few empty squares and long blocks lying across the target’s path create those bottlenecks. That is why the later levels have only two empty squares.

More block puzzles

Finished every level? Take on the 4×5 classic in klotski and check your route against the shortest klotski solution. For a different kind of thinking, read our block puzzle tips and tricks and try the tetromino puzzle or the wood block puzzle.