How to play
Unblock Car
Also known as Sliding block puzzle, Traffic jam puzzle, Rush Hour, Car escape puzzle
- 100K+ downloads
- On Google Play since 2022
- Free to play
What is Unblock Car?
Unblock Car is a sliding block puzzle set in a gridlocked car park. Every vehicle can only slide along the direction it faces, so freeing the red car means moving the right blockers in the right order. There is no timer pressure or chance involved, just a chain of consequences you have to unravel.
How to play Unblock Car
Setting up the board
A rectangular grid, classically 6x6, is packed with vehicles that are two or three cells long, each lying either horizontally or vertically. One vehicle, usually red, is the target, and a single gap in the border is the exit. Everything else is empty space, and there is deliberately very little of it.
How it works
- Each vehicle slides only along its own axis: horizontal ones move left and right, vertical ones move up and down.
- Vehicles can never rotate, be lifted off the board, or jump over another vehicle.
- A vehicle may slide any number of cells, provided every cell it passes through is empty.
- Only the target vehicle can leave the board, and only through the exit.
- Sliding one vehicle in one direction counts as a single move, however far it travels.
- Nothing is hidden and nothing is random, so every puzzle is solvable by reasoning alone.
How to solve
You win the moment the lane in front of the target vehicle is completely clear and it can slide straight out through the exit.
Solving tips
- Work backwards from the exit. The only vehicles that absolutely must move are the ones sitting in the target's lane between it and the exit. Identify those first and ignore everything else until you know what is genuinely in the way.
- Trace the blocking chain. For each blocker, ask what stops it from sliding far enough to clear the lane, then ask the same question about that piece. The chain is usually three or four deep, and the correct first move is at the far end of it.
- Move the least constrained pieces first. Three-cell trucks pinned against an edge have almost no freedom, so treat their positions as near fixed and plan routes around them.
- Watch the empty cells rather than the cars. Solving is really about shepherding the gaps to wherever a blocker needs to land, so before each move ask which cells you are freeing and which you are sealing shut.
- Resist the obvious move. Nudging the target car forward early feels like progress but consumes the very lane you need as working space.
About this puzzle
Sliding block puzzles, in which pieces move within a tray and can never be lifted or rotated, are well over a century old; classic examples include the French L'Ane Rouge (the red donkey) and Dad's Puzzle.
The car-themed version, Rush Hour, was invented by the Japanese puzzle designer Nob Yoshigahara in the 1970s.
It was first sold in the United States in 1996 by Binary Arts, now known as ThinkFun, played on a 6x6 board with twelve cars and four trucks.
The format has since become a staple of digital puzzle games under a range of names.
Frequently asked questions
No. Every vehicle is locked to its orientation for the whole puzzle, so a horizontal car only ever moves left and right and a vertical one only up and down. This constraint is what makes the puzzle work.
Every published or generated puzzle is constructed so that at least one solution exists. Arbitrary arrangements of blocks are not guaranteed to be solvable, which is why puzzles are built or verified by a solver rather than shuffled at random.
It varies by puzzle, and each board has its own optimal count that a solver can compute. Typical puzzles are solved in well under twenty moves, while on the classic 6x6 board the hardest configuration found so far requires 51 moves.
Most versions count one move per vehicle per direction, no matter how many cells it travels. Some solvers instead count steps, where each single cell of travel counts separately.
Difficulty comes from the depth of the blocking chain and from moves that look wrong, such as sliding a piece away from where it eventually needs to be. Board size and vehicle count matter far less than how tightly the dependencies are tangled.
