Unblock Car is a sliding-block traffic puzzle: a 6×6 parking lot, one red car stuck in the third row, and a gap in the right-hand wall that it has to reach. Every vehicle slides only along its own axis, so the whole puzzle is working out which car has to move out of the way of which other car, and in what order. It runs free in your browser with no download and no signup, and it suits anyone who wants a two-minute problem with a clean, provable answer.
How to Play Unblock Car: Rules of the 6×6 Traffic Grid
The board is 36 squares, six rows by six columns. Your red car is two squares long, lies horizontally in the third row from the top, and the exit is the gap in the right wall of that same row. Everything else on the board is an obstacle: cars occupy two squares, trucks occupy three. Nothing ever leaves the board except your red car, and only through the exit.
There is exactly one kind of legal move. A vehicle slides forward or backward along the direction it is pointing, into empty squares. Horizontal vehicles move left and right only. Vertical vehicles move up and down only. Nothing rotates, nothing lifts over anything, nothing jumps a gap, and a vehicle cannot pass through another vehicle even if there is space on the far side. If you drag a car sideways to its axis, nothing happens — a wrong drag costs you nothing at all.
Two rules beginners keep missing. First, a vehicle can slide several squares at once, and in standard scoring that whole slide is one move, not three. Second, your red car is allowed to move left. New players push it as far right as it will go on move one, which fills the exit lane and blocks the vertical trucks that need to cross row three. You win the moment the squares between the red car and the right wall are all empty and you drive it out.
How to Solve Any Level: Work Backwards From the Exit
Do not start by looking at the board. Start by looking at one line: the squares in row three to the right of your red car. Whatever sits in those squares is the level. Usually it is one to three vertical vehicles. Every other piece on the board is scenery until you prove it is in the way of one of those blockers. This single habit is the difference between a two-minute solve and ten minutes of shuffling.
Now use the geometry, because it removes the guessing. A vertical truck is three squares long. Above row three there are only two rows — rows one and two — so a three-long truck can never park above the exit lane. It must go down, into rows four, five and six, and that means you need free squares below it, not above. That turns a vague 'somehow move this truck' into a checklist: count the empty squares underneath it, and if there are not enough, your real job is emptying those squares. A vertical car is only two long, so it has two options, and you pick the direction with more room behind it.
Then go one level deeper. For each blocker in the exit lane, ask what is blocking it, and for each of those, what is blocking them. You now have a short chain, usually two or three links. Solve it from the far end: clear the space the deepest piece needs first, then work back up the chain toward the exit. Move the red car last. Occasionally the correct move is to reverse the red car left, freeing an exit-lane square so a truck can slide through row three on its way down.
Why Some Levels Need So Many More Moves (What 'Par' Actually Means)
Par is the shortest possible solution to that specific arrangement, and it is found by a computer walking every reachable board position and taking the shortest path, not by a designer estimating difficulty. That matters because of how moves are counted: one vehicle sliding once in one direction is one move, however far it travels. Some versions of this puzzle instead count every square crossed, which is why the same level can be described as an eight-move solve in one place and a nineteen-move solve in another. Compare your count only against the count the game itself is showing you.
Par has almost nothing to do with how crowded the board looks. A board with fifteen vehicles can fall in six moves, and a sparse board with eight vehicles can need forty, because par tracks the length of the dependency chain, not the density of traffic. The other thing that inflates par is retrograde moves: positions where you must first slide a piece away from where it will eventually sit, or reverse your own red car, before the board opens up. Those levels feel unfair because progress genuinely looks like regress for several moves in a row. Computer searches of the 6×6 board have turned up starting positions that need more than fifty moves at optimal play.
There is a real reason no shortcut formula exists. Generalised to arbitrary board sizes, this puzzle was proved PSPACE-complete by Gary Flake and Eric Baum in 2002, which in plain terms means the only reliable way to find the optimal solution is to search. So beating par is not about spotting a trick; it is about replaying a level you already understand and removing the moves you now know were wasted. Your best score for each level is saved on your device, so a level you solved in thirty-one can be ground down to par over a few attempts.
Stuck? Three Jams That Look Impossible and How to Break Them
Jam one is the ring. Car A cannot move because of B, B is held by C, and C is held by A. Every piece you touch is the wrong piece, because you keep pushing on the ring itself. The fix is to stop looking at what is blocking your target and instead find the one member of the ring that has an empty square behind it — usually against the top or bottom wall, or in a corner. Move that one, and the whole circle unwinds in order. Corners and the outer rows are not obstacles in this puzzle, they are storage.
Jam two is the packed exit lane: two or three vertical pieces sitting across row three, all apparently immovable. Nine times out of ten this is because you have been clearing space upward. Remember the three-long truck can only park in rows four to six, so rows five and six are the parking bays you actually need. Clear the bottom of the board before you touch anything in the exit lane, and blockers that looked welded in place will drop straight down.
Jam three is the frightening one: no legal move except undoing the move you just made. This is a dead end in your own path, never a broken level. Every move in this puzzle is reversible — unlike Sokoban, where a wrong push can ruin a board permanently — so a solvable level stays solvable no matter what you do. The usual cause is that you filled the last empty square in a column with a vehicle you did not need to move. Undo three to six moves and replay the same moves in a different order; most of these jams are a correct move made too early. If you are chasing par, a full reset is cheaper than a twenty-move unwind, because the reset costs you nothing on the counter.
Rush Hour, Unblock Me, Parking Jam: How These Puzzles Differ
The ancestor is Rush Hour, designed by the Japanese puzzle inventor Nob Yoshigahara in the 1970s and brought to the US market by Binary Arts, later ThinkFun, in 1996. The boxed game ships a plastic 6×6 grid, a red car, cars and trucks of two and three squares, and a deck of forty challenge cards sorted into four difficulty tiers. The exit-on-the-right geometry, the piece lengths and the axis lock all come from there, so anything you learn here transfers directly to the physical set and back again.
Unblock Me, published by Kiragames in 2009, is the same mechanic dressed differently: plain wooden blocks instead of vehicles, a target block instead of a red car, and a very large level library split between a relaxed mode and a timed-free challenge mode. Mechanically there is nothing new to learn — the blocker-chain method and the 'three-long pieces must go down' rule work identically. If you have played one of these, your skill carries over completely.
Parking Jam is a different genre wearing similar clothes. There you tap a car and it drives out along a route if the route is clear, so the puzzle is choosing the order of departures, not repositioning pieces on a grid. Klotski, the older Chinese sliding puzzle sometimes sold as Huarong Dao, drops the axis lock entirely: pieces move both horizontally and vertically and the target is a 2×2 block, which makes it a spatial-shuffling puzzle rather than a dependency puzzle. Unblock Car is the axis-locked, fully reversible, order-dependent one — if what you enjoy is untangling a chain of who-blocks-whom, this is the family member you want.
Who Unblock Car Is For (and Why It Works on a Phone in Two Minutes)
Three properties make this unusually kid-friendly, and Rush Hour has long been sold for roughly age eight and up. There is no timer, so thinking is free. There is no text, so reading level and language do not matter — the same board works for a child, a grandparent and someone whose English is their third language. And because every move is reversible, there is no fail state at all: the worst outcome of a bad move is one extra number on the counter. Kids can experiment without being punished, which is exactly how the exit-lane logic gets learned.
For adults it fits the gaps in a day. A level is typically one to three minutes, it is turn-based so you can stop mid-solve, and it runs in the browser with no download and no signup — open the page and drag. On a phone you drag a vehicle along its axis with one thumb; a drag in the wrong direction simply does nothing rather than costing you a move. Your best move count for each level is stored locally in your browser, which is what makes replaying for par worthwhile.
Be clear about what it is not. There are no accounts, so nothing syncs between your phone and your laptop, and clearing your browser data clears your saved best scores. There is no multiplayer, no leaderboard and no level editor. If you want to race a friend in real time, this is the wrong page. If you want a quiet, self-contained problem with one provably shortest answer, it is the right one.
Questions people ask
Is Unblock Car free, and do I need to download or sign up for anything?
It is free and it runs entirely in your browser. There is no download, no app store, no account and no signup form. Open the page and start dragging cars. Your best move count for each level is saved locally in your browser on that device.
Can I get a level into a state where it is impossible to finish?
No. Every move in this puzzle is reversible, so a solvable level stays solvable no matter how badly you tangle it. If you reach a position where the only legal move is undoing your last one, that is a dead end in your own path, not a broken board. Undo a few moves and replay them in a different order, or reset the level.
What counts as one move?
One vehicle sliding once in one direction, however many squares it travels. Moving a truck three squares down is one move, not three. This matters because some other versions of the puzzle count each square crossed, which is why move counts for the same layout can differ wildly between sites.
I have been stuck on the same level for ten minutes. What should I actually do?
Ignore most of the board. Look only at the squares in the red car's row to the right of it, and list the one to three vehicles sitting in them. Those are the level. For each one, work out where it can physically go: a three-square truck cannot fit above the exit row, because there are only two rows up there, so it must move down. Then clear the squares it needs at the bottom of the board first, and touch the red car last.
Is this the same as Rush Hour or Unblock Me?
It is the same puzzle family. Rush Hour was designed by Nob Yoshigahara in the 1970s and published in the US by Binary Arts, now ThinkFun, in 1996; Unblock Me, from Kiragames in 2009, is the same mechanic with plain blocks instead of vehicles. The 6×6 grid, the exit on the right, the two- and three-square pieces and the axis lock are shared, so every technique transfers between them. Parking Jam is a different genre — there you choose the order cars drive out, rather than repositioning them.
How to play Unblock Car
- Drag vehicles along their lane — cars move only forward/backward.
- Clear a path for the red car to reach the exit on the right.
- Fewer moves = higher score. Can you beat the level par?
Unblock Car is free to play online at Trivio — no download, no signup, works on desktop and mobile. Your best score is saved in your browser.