Sudoku is the most mainstream of the three, at least in the United States. The game is a grid-based number game, consisting of nine 3x3 squares positioned into a larger 3x3 square made up the subgrids. The objective is to fill each column, row, and subgrid with the numbers one through nine; each number can only appear once in each row, column, or subgrid square. Certain numbers are placed in squares to give a clue to the person playing the puzzle. Difficult is dependent on the number of freebie numbers given, as well as their location.



The puzzle is relatively new compared to other classic puzzles, and didn't take off in popularity until 2005. Even though it's popularity has only recently peaked, the game was invented over 20 years ago. It was originally invented by an American; Howard Garns is attributed with developing the puzzle game, which he named "Number Place." The misconception that the Japanese invented the game comes because the game was popular in Japan under the name Sudoku, or "single number," long before it made waves in America.

In 2004, Sudoku began its rise when it was first published in a British newspaper in November 2004. The game quickly developed into a national phenomenom. The puzzle finally made its back to the United States again. By this time, it was more than just a trivial puzzle game. Sudokus puzzles are now seen in magazines, books, video games, and TV game shows.

Due to the puzzle's amazing success, there are a variety of variants that have popped up. Sudoku puzzles can be created in several different sizes, provided it's a square number. Grids such as a 4x4, 16x16, and even a 25x25, can be found for a alternative challenge to the traditional puzzle. There are also several other restrictions which can complicate the game, such as requiring that numbers only be used once in each diagonal as well, or substituting the numbers with symbols, words, or pictures.

Futoshiki is very similar to sudoku, except placed on a 5x5 board with no subgrids. The objective is to place the numbers one through five in each column and row. However, there is one twist; there are inequalities placed between grid spots that restrict which numbers can be placed where. If there's a sign placed in between the squares, a number must be "less than" or "greater than" the number placed in the adjacent square.

Second only to sudoku, kakuro is another one of the most popular number-based logic puzzles. The black-and-white colors looks very similar to a crossword puzzle. Unless sudoku where no arithmetic is involved, kakuro requires math to solve. The objective for the player is to reach a certain sum (the clue) using the numbers one through nine no more than once each. All open squares must be used, which complicates the player's ability to reach the sum. If the clue sum was seven, there are several options. They could use a one, two, and four, or just combine the one and two into a three that requires only one square.

These relatively new number-based puzzle games have been extremely successful. As they continue to grow in popularity and complexity, expect them to one day surpass the word-based games such as word searches and crossword puzzles.