Is Moonriver a layer 2?

Could you clarify whether Moonriver is classified as a Layer 2 solution in the blockchain and cryptocurrency space? Layer 2 solutions are often designed to improve scalability and transaction throughput on top of existing blockchain networks, so it's important to understand the technical underpinnings of Moonriver to accurately answer this question. Is Moonriver built to function as a complementary layer to another blockchain network, enhancing its capabilities in a specific way? Or does it operate independently as a standalone blockchain network? Understanding these details will help us determine whether Moonriver can be accurately labeled as a Layer 2 solution.