Playpen Studios
A Hong Kong-based independent game studio building clean, accessible puzzle experiences since 2013. Sudoku.by is our most ambitious project to date.
Who We Are
Playpen Studios is an independent game development studio specialising in logic puzzles and brain games. Our catalogue includes Skillz: The DJ Game and ButaVX: Justice Fighter, but Sudoku.by has grown into our flagship platform - Combining a decade of game development experience with a genuine love of Sudoku.
"We wanted to respect the classic Sudoku mechanics while bringing something fresh to the table. Our approach focused on creating difficulty levels that would appeal to everyone - From beginners to expert players."
The Vision Behind Sudoku.by
We launched Sudoku.by with a single mission: build the most accessible yet genuinely challenging Sudoku experience available on the web. Most online Sudoku sites feel clinical - Sparse grids, tiny numbers, difficulty ratings that make no sense. We set out to fix that.
Drawing on our experience in game design, we focused on three principles: every puzzle must be solvable purely by logic, every difficulty level must be accurately labelled, and the interface must never get in the way of the puzzle.
Six Difficulty Levels, Designed From First Principles
Every difficulty level is calibrated by target clue count and required solving technique - Not by randomly removing numbers and hoping for the best.
| Level | Clues | Technique Required | Best For |
|---|---|---|---|
| Easy | 38+ | Naked singles only | First-time players |
| Medium | 32–37 | Hidden singles | Casual daily play |
| Hard | 27–31 | Naked pairs, pointing pairs | Experienced players |
| Expert | 23–26 | X-Wing, Swordfish | Seasoned solvers |
| Master | 20–22 | Multi-technique chains | Dedicated enthusiasts |
| Extreme | 17–19 | All advanced techniques | Puzzle masters |
Technical Innovation
Our puzzle generator uses a custom algorithm that builds puzzles from the ground up with specific solving paths in mind - Not by removing numbers from a completed grid and hoping for the best. Every generated puzzle is:
- Verified to have exactly one unique solution
- Solvable by pure logic - no guessing required
- Human-tested before going live
- Calibrated to match the target difficulty clue count and technique requirement
The platform is built on a modern open-source stack (Python / Flask / SQLAlchemy) with a hand-crafted vanilla JS game engine - No bloated frameworks, no unnecessary dependencies.
What Makes Sudoku.by Different
- No intrusive ads - Clean interface throughout
- 6 calibrated difficulty levels - Not just easy and hard
- Killer Sudoku with full cage-sum logic
- Daily challenges and weekly tournaments
- Global leaderboard with anti-cheat scoring
- Full techniques hub - From basics to X-Wing and Swordfish
- Printable puzzles for offline play
- 30-language support via subdomain architecture