Complex systems that just work.

A prediction league for the 2026 World Cup. Friends and family called the score of all 104 matches; a scoring engine settled the arguments.

Built as a single Cloudflare Worker: the React SPA ships as static assets, a Hono API handles auth, predictions and rankings, D1 holds the state and KV absorbs the traffic. During the tournament, scheduled jobs synced live results and news — retired now that the cup is over, the site stays up as a freeze-frame of the final table.

A competitive murder-mystery logic game, adapted from the puzzle book genre: read the clues, place every suspect on the floor plan, accuse the killer — faster than everyone else.

The heart of it is a constraint solver that proves every published case has exactly one solution before players ever see it. An admin builder composes rooms, furniture and structured clues that render as natural Portuguese sentences; players race a server-side clock with a single accusation each, solo or in teams, over an F1-style season leaderboard. Same calm architecture as the bolão: one Cloudflare Worker, D1, KV.

A Totobola-style prediction game for the Portuguese league. Call 1X2 on every matchday; correct calls earn points and half a star — stars buy doubles and triples, just like the real coupon.

Matchdays in the Liga sprawl unpredictably across Friday-to-Monday, so there is no single deadline: every match locks server-side at its own kickoff. Hourly jobs rebuild the calendar from football-data.org — new rounds appear on their own, rescheduled games move themselves — and a 15-minute results pass only spends API calls when matches are actually hot. Same calm architecture: one Cloudflare Worker, D1, and an idempotent scoring engine an admin can always override by hand.

A four-player arena game in the spirit of the bomb-laying classics: blast crates, grab power-ups, trap your friends. Room codes, online multiplayer, bots that hold their own.

The whole simulation is one deterministic Rust crate — integer-only math, seeded RNG — compiled to WebAssembly and run twice. In the browser it powers offline practice; on Cloudflare it lives inside a Durable Object, one per room, ticking 20 times a second as the sole authority on every match: the sim itself validates each move, so a modified client can't cheat physics. State streams to players as compact binary snapshots over WebSockets; the canvas just interpolates and draws the neon.

Hangman for a crowd: rooms of up to ten, one secret word, and a personal gallows per guesser. Wrong letters are yours alone — the word belongs to everyone.

After Kabum's Rust-and-wasm adventure, this one is deliberately boring tech doing a social job. The entire rulebook — turns, per-player gallows, the word-setter role the room's owner can assign and the setter can pass on, hint reveals, full-word risks, sit-outs, the persistent room scoreboard — is a single pure TypeScript state machine, shared verbatim by client and server and pinned down by thirty unit tests. A Durable Object per room wraps it with WebSockets and a 45-second turn clock, broadcasting personalized views: only the word's creator ever sees the secret, and accented letters match their plain keys, so CORAÇÃO yields to a C.