Puzzle Library
Browse our hand-curated puzzles
All Puzzles
83 puzzlesBrowse every puzzle in the library
Starter Puzzles
13 puzzlesPuzzles for new hikers starting out!
Puzzles By Difficulty
Easy
43 puzzlesSingle-insight puzzles accessible with everyday reasoning. One "aha!" moment required.
Medium
29 puzzlesMulti-step puzzles requiring persistence and systematic thinking. High school mathematics sufficient.
Hard
8 puzzlesRequires specific techniques like induction, graph theory, or advanced proofs. Multiple interconnected insights needed.
Expert
2 puzzlesDeep mathematical reasoning or research-level thinking. Advanced proof techniques and mathematical background required.
Open
1 puzzleCurrently unsolved problems with no known solution. Active areas of mathematical research.
Recommended Puzzles
Guessing Hats 1
Angry with his three wise men, the evil king subjects them to an impossible task: they’ll have to guess the colour of the hats on their heads. If any one of...
Stack of Coins 2
You and your friend have decided to make treasure hunting your weekend project. After a few weeks of treasure hunting, you guys stumble on another pirate’s...
Treasure and Locks
Thirteen pirates put their treasure in a chest. They want the chest to be openable whenever a majority of them (7 or more) agree, but not when only a minority...
Antipodal Temperature and Pressure
Assume the earth is a perfect sphere. Show that at any given time, there exist two antipodal points (points on exact opposite sides of the Earth) with the same...
100, 10, 1
Your friend, Cole, shows you his first attempt at programming: a calculator that takes in a binary sequence and does an arbitrary computation on it: If the...