2. Developer
3. 1. Celer IM Overview
   1. 1.1. Inter-chain App Use Cases
4. 2. Architecture Walkthrough
   1. 2.1. Celer IM Design Patterns
   2. 2.2. End-to-End Workflow
   3. 2.3. Fee Mechanism
   4. 2.4. CELR Token Utility
5. 3. Development Guide
   1. 3.1. Contract Framework
   2. 3.2. Contract Examples
      1. 3.2.1. Hello World
      2. 3.2.2. Hello World with Token Transfer
      3. 3.2.3. In-Order Delivery
      4. 3.2.4. Batch Transfer
      5. 3.2.5. Cross-Chain Swap
      6. 3.2.6. NFT Bridge
   3. 3.3. dApp Safeguard
   4. 3.4. Message Executor
      1. 3.4.1. Integration Guide
      2. 3.4.2. Integration Guide: Advanced
   5. 3.5. Query IM Tx Status
6. 4. Contract Addresses & RPC Info
9. 5. Audit Reports