CAPTCHA Royale turns CAPTCHAs into a competitive multiplayer game. A Rust/WASM engine generates 12 CAPTCHA types across 4 difficulty tiers. No images transmitted, just seeds. Battle Royale: wrong answer eliminates you. Sprint: pure speed. ELO matchmaking on Cloudflare Workers.
The idea started as a joke: what if CAPTCHAs were actually fun? Then I realized the core mechanic (solve a visual puzzle under time pressure) is basically a competitive game waiting to happen.
The interesting technical challenge was making it cheat-proof. The CAPTCHA engine is Rust compiled to WASM. The server never sends images, just a seed number. Both the client and server independently generate the identical CAPTCHA from that seed, so there is nothing to intercept. Answers are validated server-side by the same WASM module running inside Cloudflare Durable Objects.
There are 12 CAPTCHA types across 4 tiers. Tier 1 is what you would expect: distorted text, math, image grids. By Tier 4 things get weird: CAPTCHAs that animate and morph while you are trying to solve them, typography deliberately designed to fool OCR but stay human-readable, and multi-step chains where each correct answer reduces your time for the next one.
I wrote up the full architecture and design decisions here: https://sean-reid.github.io/blog...
Would love to hear which CAPTCHA types people find hardest, and any ideas for new ones. The generator system is modular so adding new types is straightforward.
Sean Reid