# Cross-chain Helicon is the first to realize the interconnection between blockchains through innovative Blockchain Multi Tunnel (BMT) protocol, Helicon Axis, Indicator, smart contract and other blockchain technology achievements and innovations, in order to realize the complex distributed business between the chains. The application lays the foundation. Blockchain Multi Tunnel Protocol is Helicon's original communication protocol for point-to-point information transmission between blockchains. When a user creates an account in Helicon, Helicon will generate a corresponding tunnel account according to the Blockchain Multi Tunnel Protocol and bind it to the Helicon account. When a cross-chain transaction occurs, BMT will automatically process the switch between games and chains without any involvement by users. It means that uses do not need to bother holding tokens of the chains to pay transaction fees. In the Helicon cross-chain system, smart contracts can also be used to implement transactions such as multi-asset pending orders. Including the following points: • The purchase of pending orders is implemented using smart contracts, and a purchase of pending orders is a new smart contract. • Partial matching and partial transactions are allowed for pending orders. • Cancellation of pending orders is allowed. • Matching transactions and cancellations of pending orders are all transactions that call smart contracts. • Handling fees are required for purchase pending order transactions, matching pending order transactions, and cancellation of purchase transactions. --- # 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://docs.heliconnft.com/technical-architecture/cross-chain.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.