History of Sudoku

The following is based on information derived from the Sudoku.by Editorial Team (from the website Sudoku.by):

Until I started writing this history, I always assumed that Sudoku was a Japanese game; after all, the name is clearly Japanese, right?

Well, it turns out that Sudoku was actually invented in Indianapolis, Indiana in the United States!

The game was created by a mathematician by the name of Howard Garner.

In 1979, at the age of 79, Garner submitted his game idea (called The Number Place) to Dell Pencil Puzzles & Word Games magazine. Later that year, the game was published anonymously.

Unfortunately, Mr. Garner would never see how popular his game would become because he passed away in 1989 shortly before the game would become a global sensation.

Garner's The Number Place was discovered by the Japanese company Nikoli in 1984 and they started to publish it in their magazine under the Japanese name Sūji wa dokushin ni kagiru which loosely translates to ""the digits must remain single." Later, that company shortened the name to what it's known as today: Sudoku.

In addition to the name change, though, the Japanese introduced two pivotal changes to the original rules:

1. Rotational symmetry: the given clues are arranged so the puzzle looks the same if you rotate it 180°. This makes the grid more visually balanced.
2. Minimum clues: puzzles use as few given numbers as possible while still having exactly one correct solution.

Sudoku didn't go viral until 2005, though. That journey is also interesting!

In 1997, a retired judge from Hong Kong (Wayne Gould) discovered the game in a Tokyo bookshop. Gould then spent several years writing a Sudoku puzzle generation engine. In all likelihood, that engine is a remote parent to most of the engines used in today's modern Sudoku apps.

In 2004, Gould was able to convince The Times of London to print a daily Sudoku puzzle. When The Times did publish the puzzle it was an instant hit with their readership.

By 2005 Sudoku was being published globally by hundreds of newspapers and magazines worldwide!

To quote Suduoky.by:

What makes Sudoku's story remarkable isn't just its popularity — it's the journey. A puzzle invented in Indiana, quietly improved in Japan, rediscovered by a retired judge in Tokyo, championed by a London newspaper, and finally exploding into a global daily habit for over a hundred million people.

Not surprisingly, there is an annual World Sudoku Championship sponsored by the World Puzzle Federation (WPF). The event, which originated in Italy, has been happening since its inaugural event in 2006. So, if you think you're "good", get qualified and go shoot your best shot!

How to Play Sudoku

Sudoku is an easy game to learn and that helps to make it as popular as it is.

The gameboard consists of 81 distinct cells that are divided into three groups:

1. 9 columns of 9 spaces
2. 9 rows of 9 spaces
3. 9 quadrants of 9 spaces

To solve the puzzle, the Player must place the numbers 1-9 in the available spaces while following these simple rules:

1. No digit may be repeated in any single column.
2. No digit may be repeated in any single row.
3. No digit may be repeated in any single quadrant.

A fresh puzzle is presented to the Player with pre-existing numbers already filled in.

The difficulty level of a puzzle determines the number of spaces that are pre-filled.

Sudoku Insanity! supports the following difficulty levels:

1. Easy: 45 cells are pre-filled
2. Medium: 32 cells are pre-filled
3. Difficult: 27 cells are pre-filled
4. Very Difficult: 24 cells are pre-filled

Playing Sudoku Insanity!

While Sudoku Insanity! allows you to solve the puzzle using traditional numbers, it also provides the ability to solve the puzzle using Colors and Shapes!

The game is played the same exact that instead of having to track the numbers 1-9, you have to track a series of nine different shapes or colors. It's exactly the same game, but this twist makes the game even more challenging.

Check out "Settings" where you can set the Difficulty Level and Board Style of your puzzles.

The Sudoku Solver

This feature allows you to manually enter your own board or, by entering random numbers, to create a new one. Once a valid, solvable puzzle board has been created, Sudoku Insanity! provides you with the option to immediately play that board or to simply solve it and see the solution.

While I'm not sure how popular this feature will be, I created it because of an experience I had in a doctor's waiting room. During the long wait, I started a puzzle and then couldn't finish it and didn't want to rip out the page or "borrow" the magazine.

Entering Values

To enter a value on the board, simply tap any space that was not prefilled.

When one of these cells has been selected, the keypad below the puzzle will become enabled.

Tapping a number from the keypad will place that value in the selected cell.

Annotations

It's often helpful to be able to make annotations in a cell about what you feel potential values for that cell are.

In Sudoku Insanity! an annotation can be made in a cell by first tapping the pencil that appears above the keyboard. When the pencil is active, small numbers will be written in a cell when the keypad is tapped.

Erasing a cell will not remove any annotations. Annotations may only be removed by tapping the corresponding value on the keypad while the pencil is active.

Note: If you press and hold a number on the keypad, it will become "sticky". When this happens, any other cell that you activate will automatically be populated with that stuck value. To "unstick" the keypad, simply tap the number a second time. This works for normal entries and for annotations.

Annotations are not currently supported when playing a game using Shapes.

"Setting" a Value

It is not uncommon for a puzzle board to contain annotations across a cell's "siblings" (the other cells in the same column, row, and quadrant).

When you've made a final decision about what the value of a cell is, you can "set that value" and quickly erase all annotations of the value from the cell's siblings by pressing down on that cell for a moment.

PRO TIP: This feature should not be underestimated! If you focus on a single column, row, or quadrant and use annotations to record the possible values for each cell, it is often possible to isolate a cell that will only support a single value.

Then, by entering that value and pressing down on the cell to "Set the Value", you will remove that value from all of the siblings. This can then help to identify the correct value for another cell.

Clearing Values

There are two ways to clear the value in a cell:

1. Tap the keypad value that matches the existing value in the cell.
2. Tap the erase button above the puzzle board.

Clearing a cell's value will not remove annotations from the cell. Annotations may only be removed by tapping the corresponding value on the keypad when the pencil is active.

Using the "Erase Annotations" feature from the Settings Menu will clear ALL annotations on the puzzle board.

Undo

Sudoku Insanity! will log the changes that are made on the board as you play. To Undo a series of actions, simply tap the "Undo" button above the puzzle board.

Hints

Stuck and starting to think the app is broken and that you're playing a puzzle that cannot be solved? Try using a Hint. A hint can be used by tapping the hint button directly above the game board. A hint will fill in a random unsolved space.

Yeah, it's probably considered cheating, but who's going to tattle on you?

In Sudoku Insanity! the number of available hints is determined by the difficulty level of the puzzle:

1. Easy: 10 hints
2. Medium: 6 hints
3. Difficult: 4 hints
4. Very Difficult: 2

Reset Board

This feature is available from the menu and will clear the board of all entries and set the board back to its original state.

Erase Annotations

Premium Feature

This feature is available from the menu and will remove all of the annotations that have been made on the board, but will not affect the actual value in any cells.

Erase Mistakes

Premium Feature

This feature is available from the menu and will erase any bad values from cells on the board.

This feature will not remove incorrect annotations. I went back and forth with respect to annotations, but removing them basically solves the puzzle if enough were made. My suggestion is, if the annotations seem skewed, use the "Clear Annotations" feature.

Any mistakes that are removed, whether they are the cell's value or an annotation, count against the puzzle's score.

Check Puzzle

Premium Feature

This feature is available from the menu and will check the board for errors. If errors are found, they will be highlightd in red. All correct entries will be locked and displayed in green and the cell's value will be removed from the annotations of sibling cells.

Is it cheating? Maybe, but on some of the Very Difficult puzzles there may come a time when, without this "nuclear" option, your only recourse is to start over completely using the "Reset Board" feature.

Solve Puzzle

Premium Feature

This feature will complete the current puzzle by filling in the correct solution. Any errors that were made will be shown in red.

History of Sudoku Insanity

There are literally hundreds of Sudoku games available in the various marketplaces. That you found Sudoku Insanity! is probably a result of sheer luck or because my mother told you about it!

Like other things I've developed, I created this app for myself to meet my specifications. Since I tend to "set the bar high", I hope my work meets with your approval.

If you have any suggestions or requests, please feel free to reach out. I enjoy collaborating with the folks who play my apps and am humbled when they do.

How It All Started

Back in 2010, Microsoft released its first Windows Phone. At the time, I was a consultant for a Microsoft Partner. Though most of my career was spent in leadership roles, my passion has always been programming and I constantly looked for excuses to code.

At the time, I'd never written a mobile app before. Not many folks who worked on the Microsoft platform had because the mobile app space was still relatively new.

I decided I wanted to "figure it out" and create an app.

The first thing I needed to do was figure out what app to create. Looking at the phone, the screen seemed to scream "Sudoku". It was the perfect size, Sudoku is a game I enjoy, and the abundant number of features that would be required would surely result in a rewarding training experience.

I think it took me about 2-3 months to figure out the programming patterns and complete the first version of my app.

Then, I had to get it loaded into Microsoft's store so folks could download it.

I won't bore you with the details, but let's just say that getting it published was a nightmare. Even with my internal contacts with Microsoft, I was never able to get a Developer Account properly established and get the app uploaded. In retrospect, I've never been shocked that the Microsoft App Store lost so badly to Apple & Google. It was slop shoot!

Suffice to say that I abandoned my attempts to upload the app and was happy that I could play it on my own phone which was fine with me.

Microsoft Phone ultimately died, but I've still got my original phone, still keep it charged, and have been playing Sudoku on it for years!

The Move to Apple & Google

In 2017, I completed my first app for IOS: Riverboat Gambler. That app is a free casino simulator that helps people learn how to play a tremendous number of "carnival games" that can be found in casinos around the World.

That app is extremely popular and is actually being used to train casino dealers!

That app was also written as a training exercise so I could figure out how to put an app on an IPhone or IPad. When I felt my skills had matured enough, I glanced over at my little "orphan" and tried to create an IOS version of Sudoku.

Unfortunately, at the time, I just didn't have the requisite skills to work within the screen constraints that existed. For that reason, I abandoned the idea. But, I kept the code 😎

As Riverboat Gambler gained in popularity, I was encouraged by folks in the Player Community to create a version for the Play Store. So, that's what I did. I figured out how to create an Android version of the app and now I support it on both platforms.

As I improved my understanding of Android Studio and Java and, as my skills at screen construction improved, I started to realize that Android could be a great match for my original Sudoku design and, I think it was!

I started fiddling around with an Android version of this app in 2022, but then I got distracted with life and the backlogs for the other apps and Sudoku became orphaned - again. In fact, it's been so long since I last worked on this app that someone else has already published an app in the Play Store under the name I originally used. 😂

This week, I came across the code when I was cleaning up my laptop and decided it was time to either complete the app or delete the code. So, after three days of work, here it is! There are some changes I will make overtime and the look will probably evolve over time, but it's pretty much what I want it to be. It also means I can send my Microsoft Windows Phone to the Smithsonian.

Please give me a "pass" on the screen asthectics"

To paraphrase Dr. McCoy:

"I'm a Coder - not a Graphic Artist!"

So, there you have it. After about 16 years, I'm pleased to release what was actually my first mobile app. It's a bit of a bummer than it took so long because now there are so many Sudoku games on the market. But, hey, it beats just deleting the code.

~Danny

September, 2026

Riverboat Gambler, LLC Privacy Policy

Content property of Riverboat Gambler LLC