Captcha The Flag tech

—Andy Hunt

04/27/2026

My son, Stuart, has a new game up on Steam. it’s a hilarious bit of fun, with cool tech behind it.

The game itself is a chaotic PvP first person shooter with fully destructible terrain where you need to solve quick Captchas to reload your guns. Build bridges, walls, domes, tunnels, and blow everything up while competing in teams with fellow humans in games of capture the flag for the amusement of your overlords.

Stuart and his co-programmer Johnny Rockett made a custom voxel engine with Rust and WGPU for Captcha the Flag. Making the engine from scratch means the game can run well on even mid-level hardware, while still allowing lots of chaotic items that can destroy terrain and build structures.

They use cone tracing for real time global illumination that doesn’t require a high end graphics card, and a crazy custom hybrid forward/inverse dynamics physics animation system that’s entirely GPU accelerated for character movement.