How I Built a Fast, Multilingual Crossword & Sudoku Platform (crossword.by)

TooBoo — Tue, 07 Apr 2026 20:22:34 +0000

For the past months I’ve been working on a side‑project that started as a tiny experiment and slowly grew into something much bigger — a clean, fast and multilingual platform for crosswords, sudoku and other logic puzzles: crossword.by.

I didn’t plan to “build a puzzle platform”. I just wanted a simple place to solve crosswords without ads, pop‑ups, trackers or slow scripts. But the deeper I went, the more interesting the challenge became.

Here’s the story, the tech behind it, and what I learned along the way.

Why build another puzzle website?

Most puzzle websites fall into one of two categories:

overloaded with ads
outdated and slow
limited to one language
not mobile‑friendly
or all of the above

I wanted something different:

instant loading
clean UI
works on any device
supports multiple languages
no registration
no distractions

Basically: a quiet place to think.

The multilingual challenge

Supporting multiple languages (EN, DE, FR, ES, UK, RU and more) turned out to be one of the most interesting parts.

Crosswords are language‑dependent:

clue structure
word length
letter frequency
cultural references

I had to rethink how puzzles are stored, generated and validated.

Instead of a single dictionary, I built a modular system where each language has its own word list and metadata.

This also opened the door to something cool:

children‑friendly puzzles with simplified vocabulary.

Sudoku: harder than it looks

Sudoku seems simple on the surface, but generating good puzzles is a whole different story.

I wanted:

no guessing
logical solving path
difficulty levels that actually make sense
clean grids with minimal clues

I experimented with several generation algorithms, pruning strategies and difficulty estimators. Eventually I built a hybrid approach that balances:

constraint propagation
backtracking
human‑style solving heuristics

The result: puzzles that feel natural, not random.

Performance matters

One of my goals was to make everything instant.

That meant:

no heavy frameworks
minimal JS
pre‑rendered pages
optimized SVG rendering for grids
caching wherever possible

The entire site loads in a blink, even on slow mobile devices.

Designing for focus

Puzzle‑solving is a “flow” activity.

Anything that breaks concentration ruins the experience.

So I kept the UI extremely minimal:

no pop‑ups
no modals
no animations
no dark patterns
no clutter

Just the puzzle, clean typography, and a few essential controls.

What I’m working on next

There’s still a lot I want to add:

user‑generated puzzles
community challenges
daily streaks
printable versions
more languages
more puzzle types

But even in its current form, the platform is already being used by people from different countries — which is incredibly motivating.

Try it out

If you enjoy crosswords or sudoku, feel free to try the platform:

👉 https://crossword.by

I’d love to hear your thoughts — UI, puzzle quality, performance, missing features, anything.

Thanks for reading!

Forem: TooBoo

How I Built a Fast, Multilingual Crossword & Sudoku Platform (crossword.by)