Long before Puzzuzu or Survivor, these puzzles lived in toy boxes, on friends' coffee tables, and on computers that took their time starting up. You may have met one already. You may even have sworn you'd never play it again.
Here are five classic puzzle families you can play here, with a little history and a way into each one. If you remember the numbered 15-puzzle, Classic Slide is a good place to begin.
Classic sliding tiles and the 15-puzzle
The familiar 15-puzzle has fifteen numbered tiles and one empty space on a 4×4 board. A move slides a neighboring tile into the space. Usually the goal is either to place the tiles in order, or unscramble a picture.
The puzzle is generally credited to Noyes Palmer Chapman, a New York postmaster who shared an early version in 1874. It became a craze in 1880, helped along by prizes for solving arrangements that sometimes couldn't be solved at all. Its tangled history fills an entire book, The 15 Puzzle Book: How It Drove the World Crazy.
Puzzuzu's Classic Slide uses pictures and several board dimensions. A practical starting method is to complete a row and a column, then repeat within the remaining rectangle. The Classic Slide guide illustrates individual moves and the final-pair setup that makes this method workable.
Tower of Hanoi
Tower of Hanoi asks you to transfer a stack of disks between pegs, moving one top disk at a time and never placing a larger disk on a smaller one. The rules fit in a sentence, but each new disk nearly doubles the work.
Édouard Lucas introduced the puzzle in 1883 with a story about monks moving a tower of 64 golden disks. When they finished, the world would end. Fortunately for everyone, even a perfect solution takes 2^64 − 1 moves. The same rule applies to any standard three-peg tower: with n disks, the minimum is 2^n − 1 moves. Three disks take seven moves; four take fifteen. The ETH Library's account has the story and the math.
Try three disks in Tower of Hanoi. To move the largest disk to the goal peg, first move both smaller disks to the spare peg. Move the largest disk, then move the two smaller ones on top. That is why adding a disk doubles the previous job and adds one move. Toppling Tower of Hanoi shows how to repeat the pattern on larger towers.
Sliding blocks and Orthogonal Slide
Sliding-block puzzles share Classic Slide's use of empty space, but blocks can have different sizes and only specified pieces may need to reach a goal. Moving one block can require rearranging most of the board around it.
“Orthogonal Slide” is Puzzuzu's name for this family of sliding puzzles as a nod to the site's Survivor origins. The Classic Puzzles collection includes familiar layouts such as Klotski and Pennant. Rob's sliding-block puzzle page shows just how many relatives they have.
In Orthogonal Slide, pieces keep their orientation and move separately. A two-cell-wide target moving down needs two neighboring empty cells beneath it. The Orthogonal Slide guide shows how small-block moves create that opening in Klotski.
Instant Insanity
Instant Insanity uses four colored cubes. Arrange and orient them so that each long side of the row shows all four colors. Fixing one side can spoil another.
The puzzle's origins are murky. The Smithsonian's Instant Insanity record credits Franz O. Armbruster and traces earlier versions of the idea; Parker Brothers sold the puzzle under its familiar name in the 1960s.
My personal history with this puzzle starts at my cousin's house as a kid in the 1980s. I'd solve it, scramble it, and then discover that I couldn't repeat the feat without memorizing the cubes. Naturally, I tried again trying to find a rule to solve the puzzle without using memorization.
Try Instant Insanity by noting the pairs of opposite faces on each cube before rotating at random. Those pairs constrain which colors can appear on opposing sides. Cracking Instant Insanity develops the graph-based approach to keeping track of them.
Tetravex and edge matching
Tetravex gives each tile a value on each of its four edges. Fill the board so that touching edges agree. A tile that matches the neighbor above may fail to match the neighbor on its left, so each placement has to satisfy all of its current neighbors.
I first played Tetravex on a Windows 3.1 computer. Scott Ferguson's version appeared in Windows Entertainment Pack 3, though the edge-matching idea has older origins most likely MacMahon Squares.
Tetravex is one of the few games I added to Puzzuzu without a Survivor connection. You can understand the rule at a glance, then spend a surprising amount of time finding the one tile that fits. Vexed by Tetravex explains how to narrow the choices.
Your turn
So go ahead and pick the one that used to sit on your shelf, or try one you somehow missed. Start with a few tiles in Classic Slide, or see how long four cubes can keep you busy in Instant Insanity. If an old favorite still manages to stump you, at least this time you won't have to dig through your cousin's toy box to try again.