CryptoKitties are the latest digital craze in the emerging world of cryptocurrency, allowing multi-million-dollar collecting, breeding and trading of adorable, big-eyed, virtual cats.

Bitcoin, the first crypto-currency, rose in value by 54 percent to $903 in 2016. But despite massive skepticism about digital currency, it gained another 1,245 percent to  $11,238 in 2017.

Several new crypto-currencies have also become popular, such as Ethereum.

Economists call money an “illusion,” because it refers to people’s tendency to think of paper money in nominal, rather than real terms. That means associating a face value (nominal) of money with the purchasing power (real) price levels, but paper money is not intrinsically valuable, like gold.

Finding a fun way to combine investing in Ethereum and collectibles, the venture studio Axiomzen launched CryptoKitties on Nov. 28 as a “toy built with emerging technology, the groundbreaking concept of digital scarcity, and a genetic algorithm.”

Directions to start playing the “meow” game are very easy. The user needs a safe place to “store all of your adorable CryptoKitties,” so they open a secure digital wallet app, like MetaMask, on the browser of their computer or laptop. That also provides a bank account to purchase Ether, Ethereum digital payment units.

The player then goes to the CryptoKitties blockchain trading marketplace and invests in cute virtual cryptocollectible kitties to get skin in the game. Although the Kitties were created by the early game adopters, current players can then trade a sole Kittie, or buy another, and two loving Kitties will breed an egg. The egg matures into another Kittie.

The game has turned into a viral chain letter on steroids that is clogging the nodes hosting Ethereum’s blockchain. The game has averaged 10 to 15 percent of all worldwide Ethereum daily volume since Dec. 2. CryptoKitties accounted for 50,000 trades at a volume of $3 million on Dec 4.

The game becomes interesting to participants viral once the player figures out which traits are rare. There are only 156 “jaguar” kitties and 81 “mainecoon” kitties to choose from. “Breeders” actually have DNA papers that can be tracked on the CryptoKittydex web site.

For example, Dracula is a professional Mad Scientist Kittie with a big handlebar mustache. He makes hissing sounds, loves wet food and is considering a career change to become a soap opera star. He currently is being pimped out for about $3 a trick, “siring” more Kitties.