Game world

Brain teasers online

64 games in 4 variants

Brain teasers are for the moments when you feel like thinking a little. Fill in sudoku and its relatives kakuro and killer sudoku, solve nonograms, find your way out of a maze or race the clock with sums. Many games offer several difficulty levels.

Showing 48 of 64

Which variant should you pick?

A short explanation of every variant. The button below shows only those games.

Brain training23 games

Short games for focus and logic: nonograms, lights you switch on and off, higher or lower, peg solitaire and tic tac toe.

Sudoku16 games

Sudoku in many forms: classic, mini, killer, X, kakuro, calcudoku and wordoku with letters. Each asks you to place numbers or symbols without repeats.

All games: Sudoku

Mazes13 games

Mazes from simple to tangled: guide a ball, a snake or a character to the exit, collect keys or fill every corridor in one stroke.

Maths12 games

Numbers and arithmetic turned into games: making ten, quick sums against the clock and mahjong with numbers.

Rules for games in this world

Short guides to games in this world, with rules and tips for beginners.

Game rules

Sudoku

Sudoku rules explained simply, with solving techniques for beginners and a quick tour of variants: mini, killer, sudoku X and picture sudoku.

Read the rules

Questions about brain teasers

What is the difference between sudoku and killer sudoku?

In standard sudoku every row, column and 3x3 box holds the numbers 1 to 9 without repeats. Killer sudoku adds cages with a given sum and often starts with no numbers filled in.

What is a nonogram?

A picture puzzle: the numbers beside each row and column say how many cells in a row are filled. Fill them in correctly and a picture appears.

Are there daily brain teasers?

Yes. Daily Sudoku, Daily Kakuro and similar games have a fresh puzzle every day, and there are many more in the Daily challenges world.