Ali El Rhermoul and Jon Radoff's team at the a16z Tech Week AI/Virtual Worlds Hackathon won grand prize: it's a multiplayer online game featuring a persistent world, generative AI for storytelling (Anthropic Claude) and immersive environments (Blockade Labs, Scenario) and a client/server architecture using Beamable + Unity to create a persistent world using a new technique called "semantic programming," which uses an XML-based format to provide consistency between generative and game components.