OpenAI's GPT-5.6 Sol Ultra Generates a Playable Minecraft-Style 3D Game Written Entirely in Lean 4

OpenAI's flagship GPT-5.6 Sol Ultra generated a playable, Minecraft-style 3D voxel game written entirely in Lean 4, a language normally reserved for formal mathematical proofs — completing the initial build in roughly one hour and 44 minutes and fixing its own rendering bugs. The demo, showcasing a compact open-world game dubbed "Axiom: First Light," has drawn attention as an unusual stress test of the model's reasoning and coding abilities.