Is Horizen a layer 1?

I'm curious to know if Horizen, the blockchain project, can be classified as a layer 1 blockchain platform? I've heard that layer 1 blockchains are the foundational, CORE infrastructure that supports various decentralized applications and smart contracts. Given Horizen's focus on privacy, scalability, and interoperability, does it indeed operate as a layer 1 blockchain, providing a secure and robust base for developers to build upon? Or does it function more as a layer 2 solution, enhancing the functionality of existing layer 1 blockchains? Clarifying Horizen's position within the blockchain architecture hierarchy would greatly aid in understanding its potential and applications.