• Choosing a codebase
• The config file
• Consensus
• Abstraction
• P2P networking
• Privacy-preserving protocols
• APIs
• User interfaces
• Efficiency improvements
• Virtual machine optimization and precompiled contracts
• Denial-of-service attacks and Security
• The Merkle Tree
• Transaction Parallelizability
• Smart Contract Safety
• State channels
• Privileged Accounts
• Changing the Consensus Set