The first blockchain game CryptoKitties exploded onto the cryptocurrency market in late November 2017. To date, the game has 274,615 sales with over $19.35 billion USD sold.  Built on the Ethereum (available on Coinbase) blockchain, CryptoKitties uses ETHer (ETH) as its in-game currency. The top digital cat within the entire game sold on December 6th, 2017, for 253.33 ETH which at the time, was worth $110,707.16 USD. That same cat is now worth $299,444.07 USD.