Brain Teasers
- 3
- Archimedes' Laboratory
- Recreational mathematics including puzzles to make and solve, tessellations, geometric puzzles, optical illusions, and curiosities.
- 5
- Brain Teasers
- Brain teasers, riddles, logic puzzles and problems, paradoxes, optical illusions, IQ tests and logical games.
- 7
- Braingle
- Includes a huge collection of user submitted and rated brain teasers and riddles. It also has a message board and some unique multi-player games.
- 8
- Curiouser.co.uk
- Paradoxes, puzzles, games, optical illusions, poetry, curious facts, and quotations.
- 11
- Professor Tangent
- Have fun with games, puzzles, brainteasers and humor as you learn about logic and analysis.
- 12
- Puzzle Contest Center
- Riddles, brainteasers, cryptograms, anagrams, and logic puzzles. Compete in eight new contests monthly.