90% Faster, 100% Code-Free: MLLM-Driven Zero-Code 3D Game Development

3D game development demands expertise across programming and engine configuration, limiting non-professional participation. Existing automated approaches face three challenges: (1) scope limited to 2D content or isolated code snippets; (2) manual integration of generated components into game engines; and (3) suboptimal interactive game logic and state-transition management. A critical gap remains in translating MLLM outputs into production-ready, executable projects within engines like Unity and Unreal Engine. We introduce UniGen, the first end-to-end multi-agent framework for automating runnable 3D game development from natural language. UniGen employs a Planning Agent to convert requirements into structured blueprints, a Generation Agent to produce executable C# scripts, an Automation Agent for component binding and scene construction, and a Debugging Agent for real-time error correction. Evaluated on three game prototypes, UniGen eliminates manual coding and reduces mean development latency by 91.4%. The agent implementation and prompt templates are available at https://github.com/yxwan123/UniGen.