Singing Marbles

Inspiration

Know those tiktok videos where marbles are falling down and the lowest wins the grand prize. Well we wanted to make that in 5 hours cause we taught it would be cool.

What it does

Each marble is represented by a popular character (Spongebob, Obama, etc.) and they all sing any song that the user provides, and then the character thats currently in the lead will sing that song with its SOUL.

How we built it

We built a real-time browser game with a React + TypeScript frontend and a Node.js/Express backend.
Physics and marble movement are handled with Matter.js, while Socket.IO keeps race state synced live between server and client.
For AI voice conversion, we integrated the Musicfy API (voice list + convert voice flow).
We added persistence with SQLite (saved characters + generated outputs) and local file storage for generated audio so songs remain available after reloads.

Challenges we ran into

Normalizing Musicfy API responses and handling inconsistent payload shapes
Preventing “Unknown” character/song labeling and mapping outputs back to the correct character
Keeping race rendering, leaderboard updates, and audio playback in sync
Supporting character persistence (name/image/song) across app restarts
Safely removing players mid-race without breaking physics/race state

Accomplishments that we're proud of

End-to-end flow from voice selection -> character creation -> song conversion -> live race playback
Persistent character library with reusable songs
Leader-aware audio switching (the top racer’s song plays automatically)
Real-time multiplayer-style race updates with smooth camera tracking