Bubble Sudoku › About

Hi, I’m Kasey.

I made Bubble Sudoku. Here’s how it happened.

How it started

When I was 10, I taught myself how to play sudoku. I learned the basic rules, then figured out the rest over time by spotting patterns. The logic hooked me right away, but I always thought it would be much more fun in color.

Sudoku is still the first thing I reach for when I have a few minutes to fill, whether I’m on a plane, sitting in a waiting room, or have some downtime at work. It’s perfect for those in-between moments. You never have to finish a puzzle in one sitting, and it’s just as easy to get back into, even after days, weeks or months away.

But the apps I tried never had everything I wanted. Some were hard to follow, and others I just didn’t enjoy looking at. I wanted to get better, and I wanted an app that looked good while it taught me.

So I decided to teach myself a new skill and build my own: sudoku in color, with hints that explain every step, simple lessons directly in the app, and Spot It boards to practice one technique at a time.

“Too boring”

The first time I showed it to a friend, it was barely a game. Just a board and some bubbles. The colors weren’t right, the boards weren’t accurate, and the puzzles didn’t always work.

She had never given sudoku a chance because it looked “educational” and “too boring.” But once she learned the basics, she was hooked. Her excitement changed my perspective. What I thought was just a new skill became something I was really proud of. She helped me see its potential and pushed me to keep moving forward.

Built from scratch

Getting it right took far longer than I expected. I thought sudoku would be an easy app to build. It’s a simple set of rules! I didn’t realize how much theory goes into building an accurate board. The parameters are incredibly sensitive to tune, and the puzzle engine alone took five months to build. And I’m still fine-tuning it today!!

Now every board has exactly one solution. Each difficulty level is built on its own set of techniques, so every new technique I add sends its whole difficulty back to be re-tuned and retested.

The hints were the hardest part

There are about 6.7 sextillion ways to fill a sudoku grid. That’s 6.7 billion trillion, to put it into perspective. If you completely filled in one grid every second, it would take more than 200 trillion years to finish them all.

There’s no way to write a hint for every possible board ahead of time, and even if there were, it would take up a huge amount of space on your phone. Since you can ask for a hint at any moment, on any board, I had to build a better way: a system that looks at the board in front of you, instantly finds the next step, and teaches it.

Finding the right next step was hard. Finding a way to teach it was even harder. Each lesson is a template that has to explain a multi-step move clearly on any board, at any point in the game, in every language, following each language’s own grammar. Every hint walks through the logic step by step, even for the hardest technique in the game, so you always walk away knowing a little more.

That also means you don’t need to know every technique before you play. Getting stuck is the best way to learn, and when you do, a hint shows you exactly what you need.

Drawn by hand

Every badge, trophy and piece of art in the app is drawn by hand, on my iPad. Drawing more than 80 pieces was more than I ever anticipated, but it was important to get it right, and hand-drawn art was the way to do it. Bubble Sudoku wouldn’t be the same without it, so I’m glad I put in the dozens of hours.

It will never be done

For months, I worked 12-hour shifts during the day, then came home and worked on the app at night. I pulled all-nighters and fell asleep in front of my laptop more times than I can count.

It always felt like the finish line was just around the corner. Every week for five months, I said “just one or two more weeks” until launch. Then I realized it will never really be done. There will always be something to improve. It was a huge relief when I finally launched. It wasn’t perfect, but it was out there!

Some of what comes next is up to you. Tell me which technique you want me to add next, and I’ll get started on it as soon as I can!

More than a game

Running Bubble Sudoku goes far beyond building the app. I was never planning to start a company, but I founded Pop Logic Studios to release Bubble Sudoku, and now I’m learning how to market an app, too. It takes 12 different services to keep everything running. Building it alone has been hard, and I’m proud of how far it’s come.

If you’ve never played sudoku, I hope this is the version that convinces you to give it a try.

Thank you

To my mom and dad, Sheila and Linda: thank you for all your support and feedback, and for spreading the word.