What code does Polygon use?

I'm curious to know, what code does Polygon utilize in its blockchain network? Is it a derivative of an existing popular blockchain framework, or is it a completely unique and proprietary codebase? Understanding the technical foundation of Polygon's infrastructure is crucial in evaluating its potential for scalability, security, and interoperability within the broader decentralized ecosystem. Can you elaborate on the specifics of Polygon's codebase and any unique features it might offer?