# Smart Contract Interface via MIDL (EVM on Bitcoin) Developers can think of Helios as an **EVM-based application, but one where transactions are triggered through Bitcoin transactions**. The Helios contracts (for lending pool, etc.) run in the MIDL execution layer, which is EVM-compatible. Thus, in principle, they have functions analogous to an Ethereum lending protocol (e.g., `deposit(uint amount)`, `borrow(uint amount)`, etc.), and state variables tracking who deposited what, outstanding loans, interest indices, etc. ## EVM Compatibility Because Helios contracts are like Ethereum contracts, developers can potentially write or audit them using Solidity and familiar tools such as Hardhat. Helios’s core contracts would be opened to public, and any integration (like oracles or DEX for collateral swap) might also involve standard smart contract development. The grunt of work besides the smart contracts written on Solidity would be interaction with Bitcoin web wallets such as Leather or Xverse that supports MIDL. Developers need to bear in mind that both EVM(MIDL) and BTC mainnet access may be needed upon user interactions. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://helios-finance.gitbook.io/helios-finance/for-developers/smart-contract-interface-via-midl-evm-on-bitcoin.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.