K-pop's biggest stars, from BTS to Seventeen, have danced routines that Youngjun Choi choreographed. They co-founded the startup MVNT to build an AI system for programmable dance, much like Suno, the generative AI music platform. He's seen stars rise and fall into obscurity, and been the unseen hand behind some of the industry's most famous routines. The platform then uses the choreography database to power AI tools, allowing users to input music and generate new routines. MVNT is in the process of building its app and database — it has reached 1,100 users, and notched more than 2,000 dance routines created on the platform.