CryptoKitties is a game built on the Ethereum Blockchain. Each CryptoKitty is one-of-a-kind and 100% owned by the user. This is made possible by the use of NFT (or Non-Fungible Tokens) technology. Non-Fungible Tokens are special types of tokens that represent ownership of a unique asset on the Blockchain. These tokens cannot be replicated, taken away, or destroyed. Every CryptoKitty is a NFT and the user buying it has its true ownership.
The supply of kitties is limited by certain factors such as reproduction rate, which decreases every time they are bred. The first generation requires under an hour of rest time after having a kitty; After 6 breeding cycles, the slowest generation takes 1 week between each breeding cycle before they can reproduce again.
The kitties can be bred with one another to produce a new CryptoKitty. The baby kitties are born into with a combination of their parents' genetics.
- Some of the kitties were being sold for over $100,000 worth of Ethereum.
The CryptoKitties have complex personalities and profiles describing their occupation, hobbies and interests.
There are detailed character descriptions of the CryptoKitties. Some of the kitties are Dispensary clerks, Metallica fans, or Chanel shoppers.
CryptoKitties had >11% of the total ETH volume in the days following the release. It was a viral game that spread in popularity rapidly. this was worth close to $100 million in volume within 24 hours. By the end of 2017, Cryptokitties got so popular that it amounted to 12% of the total transactions occurring on the Ethereum network thereby clogging it. The most expensive feline, named Genesis, was sold for 246.9 ETH which amounts to about $114,000. Genesis was actually the first cryptocat to come around. 
Different kitties are more rare than others, based on Genetic traits that appear less often. These can be Recessive causing the specific Phenotypes to be more infrequent than others.
For instance, there are some with large, glowing eyes, thin Mustaches that look like Salvador Dalí's mustache.
In addition, only 18% of the total genes have been released so far, allowing for a controlled introduction of new traits into the Gene pool.
Because the genome is 256 bit, there are roughly 4 billion combinations of crypto kitties. The genetic code is a long hash code and it controls things like tail size, hair style, facial gestures, stripes, spots, whiskers and even the background of the kitty.
The creator of the kitties was McElroy Flavelle, a Virtual reality engineer. Another Software engineer, Nick Johnson. He was responsible for bug testing the site.
Players purchase, breed and trade virtual cats that have different visual features of varying levels of rarity. Players must purchase Ether cryptocurrency to join the game, and spend it to perform each breeding and trade action within the game.
The virtual cats are breedable and carry a unique number and 256 bit distinct genome with DNA and different attributes (cattributes) that can be passed to offspring.
Several traits can be passed down from the parents to the offspring. There are a total of 12 'cattributes' for any cat, including pattern, mouth shape, fur, eye shape, base color, accent color, highlight color, eye color, and optional wild, environment, 'purrstige' and 'secret'. Other features like cool down times are not passed down but are instead a function of the 'generation' of the offspring, which is one more than the 'generation' of the highest 'generation' attribute.
A CryptoKitty does not have a permanently assigned gender. While they can only engage in one breeding session at one time, each cat is able to act as either matron or sire. There is a 'cooldown' time that indicates how soon the cat can breed again, which goes up with the number of breeds, capped at one week.
The virtual cats are static images that can only be purchased, bred and sold. The game has no goal.
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