## The story behind Tessera

A week after being made redundant from his role as Senior Designer at a Swedish energy startup, Paul Cooper shipped a daily word puzzle.

Tessera is a 4×4 grid where every row spells a four-letter word, and every column spells a four-letter word too. Players start with the letters scrambled and swap two tiles at a time to solve. There's one puzzle a day, the same for every player worldwide, resetting at midnight UTC. It takes about a minute to play, less if you're good. The whole thing lives at [tesserapuzzle.com](https://www.tesserapuzzle.com), with no app to download, no signup, and no ads.

Cooper built it solo over seven days following his redundancy, using AI tooling end-to-end — design, code, dictionary curation, deployment, and a Spanish localisation that launched a few weeks later. It is the kind of project that, in 2023, would have taken six months of evenings.

The most interesting design problem turned out not to be the mechanic but the dictionary. Cooper's first prototype used SOWPODS, the official Scrabble word list — and kept generating puzzles where the gold solution was "ESES" or "PSST". Technically valid four-letter words. Emotionally infuriating. He ended up curating a 2,000-word list using Wikipedia frequency data, intersected with SOWPODS, so that the puzzle's solutions are words people actually use. The top ten gold words are now AREA, ARIA, UREA, ENDS, ALOE, ELSE, IDEA, TSAR, ORAL, ILIA — words you'd recognise from a newspaper, not a Scrabble tournament.

On the AI workflow, Cooper is careful to make a distinction that he says the broader discourse hasn't quite caught up with: "The AI didn't make the game. It removed the friction between having an idea and shipping it. That changes which projects get built. The threshold for 'worth attempting' just dropped a lot." He's quick to add that AI didn't replace the design work — choosing the tier names ("Tenacious" instead of "Struggling" for the slowest solvers), the green-outline hint that signals warmth without giving the answer, the decision to use strict word matching over a more permissive rule — those decisions stayed entirely his. AI made him faster at the parts he was slow at, and exactly as fast at the parts that needed taste.

The Spanish version went live in May 2026, with its own separately curated dictionary. Cooper is currently looking for senior product design and UI engineering roles, and treats Tessera as a small piece of public evidence about how he works now. A more technical write-up of the build is at [pjcooper.design/blog/meet-tessera](https://www.pjcooper.design/blog/meet-tessera).