What Is a Brain Teaser? Its Parts, Kinds and What Makes One Good
A brain teaser is a short puzzle with a hidden trap, a moment of insight and one checkable answer. Its kinds, its neighbours and what makes a good one.
Riddle10 blog
Puzzle science and history
What research says about riddles, puzzles and thinking.
Where puzzles come from and what mathematics and research say about them. The articles here cover the history of classic puzzles, the ideas behind them and what counts as a puzzle, with sources listed at the end of each one.
Start here: history of puzzles, what makes a good puzzle, what makes a puzzle hard
What Is a Mechanical Puzzle? Parts, Kinds and Why They Get Hard
A mechanical puzzle is an object you solve by moving or fitting its parts. Its parts, kinds, rules and why half of a sliding tray's positions are unreachable.
Types of Puzzles: Six Groups by the Material You Work With
Word, number, picture and spatial, physical piece, pure logic and chessboard puzzles: what each type of puzzle uses and how to begin.
What Makes a Puzzle Hard? Search, Outcomes and Hidden Rules
Four things make a puzzle hard: a huge search, tests that reveal little, long solutions and hidden constraints. What the research shows for each.
What Makes a Good Puzzle? One Answer, Fair Clues and an Aha Step
A good puzzle has one answer, fair clues, a clear goal and an aha step. What research on logic, weighing and dissection puzzles shows about each.
Why Some Puzzles Are Computationally Hard, Even for Computers
Why some puzzles are hard for computers: positions grow too fast to check, best answers are NP-hard, and clever estimates cannot remove the worst cases.
Puzzle With a Unique Solution: How Designers Make Sure
A good puzzle has exactly one answer. How designers and researchers check every possibility so a puzzle ends with a single solution.
How Many Latin Squares Are There? Counting Puzzle Grids
Latin squares go from 12 of order 3 to a 37-digit count at order 10. How the counts were found, how larger ones are estimated, and how grid loops are counted.
How Puzzle Difficulty Is Measured: Solve Rates to Dead Ends
Puzzle difficulty is measured by solve rates, ratings, dead ends and solution length. What research says each method shows and misses.
How Computers Solve Puzzles: Search, Estimates and Logic
Computers solve puzzles by searching a network of positions. See breadth-first search, A*, greedy search and logic programs on one worked example.
Why Some Peg Solitaire Puzzles Are Unsolvable
A colouring trick shows why some peg solitaire puzzles can never end with one peg, and what research found about symmetric and unique-solution boards.
Dissection Puzzles: Cutting a Triangle Into a Square
Any polygon can be cut into any other of equal area, but how few pieces? Why four convex pieces is the record for turning a triangle into a square.
Chess Board Puzzles: How Many Queens Fit, With and Without Pawns
From eight queens to a quarter of the board: what peer-reviewed papers say about queens, pawns, dragon kings and the distance between squares.
Packing Puzzles: The 70 Square and the Thirty Colour Cubes
Why 24 squares cannot tile a 70 square, how a shorter proof is being built from the edges, and how 30 painted cubes copy each other.
What Is a Puzzle? A Definition From Mathematics and Puzzle Design
A puzzle has a fixed start, fixed rules and a clear goal. What research says makes a puzzle good, what makes it hard, and when it has no solution.
History of Puzzles: Six Classic Puzzles and Where They Came From
A short history of puzzles: eight queens in 1848, the 15-puzzle from the 1870s, the 70 square, coin weighing, truth-tellers and colour cubes.