They're addictive, engrossing and maddening. Sliders have been around for well over a century, but you still may have a lot to learn about these braintwisters.

### What is the first sliding puzzle commonly known as?

- Rubik's Slider
- The 15 Puzzle
- Tic Tac Toe

### What shape were the pieces of the original sliding puzzle, the 15 Puzzle?

- square
- triangular
- circular

### How many 15 Puzzle configurations are solvable?

- all of them
- half of them
- all except one

### The 15 Puzzle became popular in which year?

### Who was the inventor of the 15 Puzzle?

- Sam Loyd
- Noyes Chapman
- P.T. Barnum

### How can sliding puzzle pieces be moved?

- by jumping over another piece
- by flipping them
- by moving them into an empty space

### True or False: The simpler a sliding puzzle's design, the easier it is to solve.

### Why was the Pennant Puzzle of 1909 harder to solve than earlier sliding puzzles?

- It had no frame.
- It used rectangular pieces.
- The pieces were all the same color.

### True or False: Even computers have a hard time solving sliding puzzles.

### Ma's Puzzle, released in 1927, introduced what element into sliding puzzles?

- T-shaped pieces
- L-shaped pieces
- Z-shaped pieces

### What is the key to solving sliding puzzles?

- moving two pieces at once
- converting the puzzle to a mathematical formula
- There is no key.

### The Japanese sliding puzzle Sokoban represents what kind of worker?

- taxi dispatcher
- warehouse manager
- airline pilot

### What makes Sokoban especially difficult?

- Pieces can be pushed, but not pulled.
- The pieces are different colors.
- The game has a warp factor that randomizes the tiles.

### What professional group has a history of sliding puzzle analysis?

- mathematicians
- philosophers
- psychologists

### When mathematicians judge a puzzle PSPACE-complete, what does this mean?

- The puzzle is complex and difficult to solve.
- The puzzle has a certain number of empty spaces.
- The puzzle cannot be solved except by a computer.

### What claim is made for the computer-designed puzzle called Quzzle?

- It's a puzzle no one has ever solved.
- It's the best puzzle for a child.
- It's the most difficult simple sliding puzzle.

### Rubik's Cube, a relative of the sliding puzzle, created a sensation in which decade?

### How long did it take chess champion Bobby Fischer to solve Rubik's Cube?

- 5 minutes
- 2.5 minutes
- 25 seconds

### What is the world's record for solving Rubik's Cube?

- 21.71 seconds
- 15.66 seconds
- 5.66 seconds

### Which renowned puzzle inventor has an annual puzzle design award named for him?

- Feliks Zemdegs
- Nob Yoshigahara
- Junk Kato