CryptoKitties was the first blockchain game to gain mainstream interest[1], focused on the breeding and collection of virtual cats. Launched in 2017 by Dapper Labs, it became notorious for clogging the Ethereum blockchain due to a large number of players[2]. In the future, it will be integrated with the Flow blockchain, created by the same company. Currently, each cat is an ERC721 token, and some of them remain among the most highly-valued smart property on the market according to the last sale price.