The blockchain with the most widespread use of smart contracts is Ethereum. Of all the smart-contract-capable networks presented here, it is not only the one with the largest use, but also has the largest ecosystem of public distributed applications. One of the reasons that Ethereum is so popular is that its representation of smart contracts is relatively intuitive and easy to read. In this section, we are going to look at a common Ethereum-based smart contract that fulfills all four of the preceding criteria and is relatively easy to understand: a token sale contract. The following code will be written in Solidity; for more details, please see Chapter 13, Solidity 101, and Chapter 23, Understanding How Etherum Works.