Klotski

The World's Most Reused Difficult Trick

This Stock Puzzle consists of a 4x5 board with sliding blocks. One block is 2x2; the other blocks are 2x1, 1x2 and 1x1. The goal of the puzzle is to get the 2x2 block into the bottom position.

There are variations of this puzzle based on differences in the initial position, or in the number of blocks of various sizes. It is sometimes known as the Dad's Puzzle, where the theme is a father trying to move around pieces of furniture, or the Pennant Puzzle.

Examples of Klotski include:

Video Games

• The "World's Most Difficult Trick" in Lufia II.
• The furniture puzzle in The 11th Hour.
• The "Last Pedestal of Buddha" in Quest For Karma.
• The Archie Comics Web site has a Java puzzle called "Traffic Jam", in which the player must move Archie's red car to the exit by rearranging other vehicles in the parking lot.
  • A physical version of this has been sold under the name "Rush Hour".
• The old Windows game pack came with Klotski: three levels of eight puzzles each, starting with several variants of the puzzle described above, then moving through more complex puzzles and culminating in a 27x27-square puzzle titled Sunshine. This final puzzle, requiring some 2000-plus moves to get the five-by-five block to its home, takes not so much ingenuity as patience: with only five squares' leeway, each square required for a single move of the red piece, work the red piece down to the door, then tediously work it around the edge of the puzzle and back up to the top.
• The GNOME desktop environment includes a straightforward Klotski game in the GNOME Games package.
• And if you thought this kind of puzzle was hard enough, don't even look at Bricks, a Windows/DOS Klotski clone that includes, among other things, magnetic pieces, walls that pop up if you slide something over them, pieces that can't move until a certain "key" piece is brought to a certain position, and unconnected groups of pieces that move as one unit. And that's just in the first installment.
• This type of puzzle appears in the Professor Layton games, naturally. Obscenely difficult versions are also the final puzzles in each game.
• The Adventure Game Companions of Xanth includes an optional Klotski puzzle.
• The video for Rockman.EXE Axess's ending theme, Hikari Todoku Basho, has a short animation of the puzzle being solved in the background near the start of the video.

Real Life

• The International Obfuscated C Code Contest had a winning entry one year that solved this puzzle. Here's the catch: When presenting its moves and the current state of the board, it would print out valid C code (obfuscated to look like the blocks)... which actually compiled, into a program that did the same thing, but faster. Crowning Moment of Awesome for the entire study of computer science.