Zen Sudoku for Palm OS

Reviewed by: Howard Carson, March 2007
Published by: Deluxeware & Island Labs
Requires: Palm OS 5 1.1MB free memory
MSRP: US$12.95

Normally we don't review inexpensive Palm OS, smartphone or Windows Mobile/Pocket PC games, but Sudoku is a craze that's no longer the original little fan game it was after Dell Magazines first introduced its version in the 1970's. In fact, Sudoku (after expriencing wild growth in popularity since 2001) seems to have settled into a well deserved place in the pantheon of programs that are must-haves for every Palm OS, smartphone or Windows Mobile/Pocket PC. The best of breed for Palm OS right now seems to be Numberz, made by Jampaq Software. Contenders for the Palm OS Sudoku crown have got to beat Numberz before they can reach for the top. Zen Sudoku has stepped up.

According to Wikipedia's excellent article on the subject, Sudoku puzzles are actually a special case of Latin Squares—any solution to a Sudoku puzzle is in fact a Latin square. Sudoku imposes the additional restriction that 3×3 subgroups must also contain the digits 1–9 (in the standard version). This particular type of puzzle as we know it was first published in the late 1970’s in Math Puzzles and Logic Problems magazine by Dell Magazines. The name given by Dell to these puzzles was Number Place, as they are still called by this company until today. Dell took Euler’s Latin Square concept and applied it to a 9x9 grid with the addition of nine 3x3 sub-grids, or boxes, each containing all numbers from 1 to 9. So the Sudoku concept was not invented in Japan as many people may believe, but the name Sudoku was. In 1984, Nikoli, Japan’s leading puzzle creating company, discovered Dell’s Number Place and decided to present it to Japanese puzzle fans. The puzzles, which were first named Suuji Wa Dokushin Ni Kagiru, ("the numbers must be single" or "the numbers must occur only once") quickly became popular. In 1986, after some important improvements were added mainly by making symmetrical patterns and reducing the number of given clues, Sudoku became one of the best selling puzzles in Japan. Realizing that the only problem with the Sudoku puzzles was their long name, Kaji Maki, the president of Nikoli abbreviated it to Sudoku: Su = number, digit; Doku = single, unmarried. Today there are more than 600,000 copies of Sudoku magazines published solely in Japan every month.


Zen Sudoku (and Sudoku in all its guises) is a deceptively simply game. It takes place on a board divided into a grid of 81 squares divided into 9 sets of 9 squares (3x3 subgroups). The goal is to place one instance of the numbers 1 through in each column and row, with all of the numbers 1 through 9 also appearing in each of the 9 sets of 9 squares. Each game begins with some numbers already placed strategically on the board to help you get started. Easy levels provide a lot of starting numbers. As you progress to more difficult levels, there are fewer and fewer starting numbers provided. As well in the more difficult levels, the few starting numbers are placed in positions which offer little or no hint for other number positions.

At all levels of game play, you'll find that there seem to be several possible numbers that can be placed in most of the empty squares. The thing is, there's actually only one correct solution for each board. Zen Sudoku, like most of its competitors, offers a feature called Pencil Marks which essentially allows you to mark down the possibilities for each empty square, gradually eliminating the possibilities as you find more and more correct numbers. But because there are often several incorrect possibilities for each of the empty squares, it's also possible to play to a point where you can't make any more moves and end up with unsolved empty squares. That means you have to backtrack. Zen Sudoku (all good Sudoku) is challenging and provides terrific exercise for your brain.

Cons: Zen Sudoku has all the right things going for it, but is unfortunately cursed with a visually distracting game board. The separation grid lines between the nine-squares are drawn using a low contrast color and we found ourselves constantly checking to ensure that we were actually estimating number positions for the correct set of squares. So why didn't we simply turn off the distracting background graphics? Because the configuration settings do not allow it. Unlike Numberz, there's no move checker to determine after a particular move if the game is still solvable. Purists might recoil at this (and some purists I know who play Numberz never use the move checker), but I personally don't find that the feature detracts from game play. Discipline and patience, when playing Sudoku, are everything. I think that it's a comparatively small effort for Deluxeware or Island Labs to tweak the Zen Sudoku game code and configuration screen so that graphic backgrounds can be turned off, add more visual contrast to the nine-square grid, and add a move checker button.

Pros: One of the Sudoku fanatics I know has color acuity issues and, unexpectedly, that deficiency allowed him to see the Zen Sudoku nine-square sections quite clearly. He wondered out loud what all the fuss was about. He loves Zen Sudoku and we certainly understand why. We just wish we could play it as enjoyably too, because the game has all the right functionality. Zen Sudoku responds quickly to taps and drags, and the number grid pop-up is a clever alternative to dragging & dropping a selected number to a square. Just tap & hold a blank square in any part of the grid and a little sub-grid pops up containing only available number choices—tap your selection. The game level and puzzle logic seems to be different than Numberz, so if you're already used to Numberz you may find that it takes significantly longer—as long as several weeks, or even a couple of months—to work your way up to the Very Hard level in Zen Sudoku. All in all it's a worthy addition to the Sudoku lineup. Download the trial version to give it a try.

KSN Product Rating:

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