Rush Hour

Rush Hour is a sliding block puzzle played on a 6x6 grid representing a traffic jam. The board contains various cars and trucks — cars occupy 2 cells and trucks occupy 3 cells — placed horizontally or vertically. Each vehicle can only slide forward or backward along its own axis (horizontal vehicles move left/right, vertical vehicles move up/down). The goal is to slide the special red car (always placed horizontally) to the right edge of the grid and off the board, freeing it from the traffic jam.

Rules

1. The board is a 6x6 grid.
2. Vehicles are placed on the grid: cars take 2 cells, trucks take 3 cells.
3. Each vehicle is oriented either horizontally or vertically and cannot rotate.
4. Vehicles slide along their orientation axis only — horizontal vehicles move left or right, vertical vehicles move up or down.
5. Vehicles cannot pass through or overlap each other.
6. Move the red car (always horizontal, usually in the third row) to the right exit of the board.

Strategies

• Work Backwards from the Exit: Identify what is directly blocking the red car's path to the exit. Then figure out what blocks those blocking vehicles, and so on.
• Clear the Exit Row: The red car's row must eventually be completely clear to the right. Focus on moving vehicles out of this row.
• Chain Reactions: Often, moving one vehicle is blocked by another, which is blocked by yet another. Trace these dependency chains to find the first vehicle in the chain that can actually move.
• Use the Edges: Vehicles pushed to the edges of the board are often out of the way. Slide blocking vehicles to the top, bottom, or left edge when possible.
• Minimize Back-and-Forth: Try not to move the same vehicle multiple times. Each move should make progress toward clearing the red car's path.
• Look for Key Vehicles: Some vehicles are "gatekeepers" — moving them unlocks several other moves. Identifying these early can dramatically simplify the puzzle.

Rush Hour was invented by Nob Yoshigahara, one of Japan's most celebrated puzzle designers, in the late 1970s. Yoshigahara, known as the "puzzle king of Japan," designed hundreds of puzzles during his career, but Rush Hour became his most commercially successful creation.

The puzzle was licensed to ThinkFun (originally Binary Arts), an American game company, which first published it in 1996. ThinkFun's version became a massive commercial hit, selling millions of copies worldwide. The game was packaged with 40 challenge cards arranged in increasing difficulty, from beginner to expert. Each card specified a starting configuration, and players had to figure out the sequence of moves to free the red car.

Rush Hour won multiple awards, including a Mensa Select award and the Parents' Choice Gold Award. Its success spawned numerous expansions and variants, including Rush Hour Jr. (a simplified version for younger children), Rush Hour Shift (with a dynamic board), and Rush Hour Safari (themed with animals). ThinkFun also released digital versions for various platforms.

The puzzle is closely related to sliding block puzzles like Klotski, and its computational complexity has been studied by computer scientists. The general version of the Rush Hour problem (on an NxN board) was proven to be PSPACE-complete by Flake and Baum in 2002, meaning it is among the hardest puzzles to solve computationally. Despite this theoretical difficulty, the standard 6x6 game with a limited number of vehicles has been completely analyzed — the hardest known configuration requires 93 moves to solve. Nob Yoshigahara passed away in 2004, but his legacy lives on through Rush Hour and his many other puzzle designs.