Rethinking Sudoku: What happens when you replace numbers with colors?
Over breakfast, a random thought popped up: What if Sudoku wasn’t about numbers at all? What if it was purely visual?
This wasn’t driven by market research or user needs, it was pure curiosity. Could the logical structure of Sudoku work with colors instead of digits? Would people be able to solve puzzles using visual pattern recognition rather than numerical logic?
Is this even solvable? The only way to find out was to build it.
Making 9 colors work
Traditional Sudoku uses 9 numbers - simple, clear, universal. But 9 colors? We had no idea if people could actually differentiate and track that many hues in a puzzle format.
Through trial and error, I developed a palette of 9 vibrant, distinct colors - each color corresponding to one number (1 to 9).
Here’s the same puzzle shown in both formats. While the logical structure stays the same, the cognitive challenge transforms from numerical reasoning to purely visual pattern recognition :
Redesigning Game UI for Colors
The shift from numbers to colors required completely rethinking the game’s visual feedback systems.
Error Indication
Added “X” overlays instead of traditional color changes. Since red is part of the game’s color palette, we couldn’t use the standard approach of turning incorrect cells red to indicate errors.
Cell Highlighting
Added clear borders around selected cells for better readability. This helps players track which cell they’re working on without visual confusion.
Smart Palette
Removed colors from selection when placed correctly 9 times. User testing revealed this made the game significantly easier, as players could instantly see which colors were still available rather than struggling to distinguish which ones remained.
Completion Feedback
Animations for completed rows, columns, and 3x3 grids. This makes the experience feel more dynamic and rewarding rather than static.
Results & key insights
The experiment proved that Sudoku absolutely works with colors.
People can and do solve color-based puzzles successfully. The biggest surprise was that users developed better color differentiation skills through practice - creating a genuinely different cognitive experience.
Users were “very confused at first, could barely differentiate colors. The more they play, the easier it gets.” This suggested people actually train their color recognition through gameplay - something numbers never require.
No single color palette works for everyone. Some users consistently mixed similar hues, while others had perfect color recognition from the start.
What I learned
Random questions can lead to valid experiments
Starting with a breakfast curiosity rather than “users need...” led to genuine insights about visual cognition and game design.
Test the core assumption first
Before worrying about features, we needed to answer: “Is this even possible?” Building a basic prototype quickly validated the concept.
Visual changes everything
Replacing numbers with colors wasn’t just cosmetic - it fundamentally altered the cognitive demands, error states, and user experience of Sudoku.
And most importantly...
Yes, it's possible!
The breakfast question turned into a real product. More importantly, it revealed how simple visual swaps can create entirely new types of cognitive challenges and learning experiences.
