CryptoKitties.

CryptoKitties is a blockchain based virtual game developed by Axiom Zen that allows players to purchase, collect, breed and sell various types of virtual cats. It represents one of the earliest attempts to deploy blockchain technology for recreational and leisurely purposes. The game's popularity in December 2017 congested the Ethereum network, causing it to reach an all-time high in transactions and slow down significantly.

On March 20, 2018, it was announced that CryptoKitties would be spun off into its own company and raised $12 million from several top venture capital firms and angel investors. The investment round was led by New York based Union Square Ventures and San Francisco based Andreessen Horowitz.

In October 2018, CryptoKitties reached the milestone of 1 million cats being bred with a volume of 3.2 million transactions on its smart contracts.

In November 2018, Dapper Labs, which was spun out of Axiom Zen as the developer of CryptoKitties, raised an additional $15 million in a venture round led by Venrock.The company doubled its valuation in this round.

Link :
https://www.cryptokitties.co