CryptoKitties - Lessons Learned

Table of Contents



Figure 1: Miku, my first cryptokitty

If you haven't heard yet, CryptoKitties is an app that allows you to collect and breed (i.e. buy and make) digital cats, which are collectibles that only exist digitally. To put that another way, these cats are crypto-collectibles (think virtual Beanie Babies or baseball cards) that you purchase with cryptocurrency (Ether in this case) that, at some point, actually had to be purchased with actual, non-digital money 1.

You may have heard about CryptoKitties in the news recently because, well, the marketplace is gonzo crazy. Some kitties have sold for over $100,000 and there are tons of speculators trying to make a quick buck.

But that's not the only reason. It's also the first Ethereum-based app (which is also called a decentralized app or dApp) that possesses these attributes:

  1. It is popular with a wide audience
  2. It's been around for almost two whole months (as of 12/21/17) and hasn't been hacked to death yet. 2

All of this together makes CryptoKitties very special and incredibly fascinating from a lot of different viewpoints. I therefore have dipped my toes in the CryptoKitties pool and learned a lot about both the app and the Ethereum system in general. Hopefully these tips will help someone else out.

Lessons Learned

It takes a LONG time to buy Ethereum using Coinbase

I've purchased Bitcoins in the past from Coinbase and it's a pretty quick and painless process after your first transaction. I expected the same process when buying Ethereum, so I was shocked to learn that I needed to wait 7 days to convert dollars into Ether.

By the way, this time frame has been consistent both of the times that I've purchased Ether.

There are other options, but when it comes to exchanging money I am very, very risk averse, and Coinbase is the biggest and most trusted cryptocurrency exchange. So I'm willing to wait.

CryptoKitties Are NOT Like Tamagotchi

You don't feed or raise CryptoKitties - you just get to look at, breed and sell them. This was also a big surprise to me at first since I figured that was the point of the "game".

So what is the point? Well, I guess that depends on who you are. For some people it's owning as many cute digital cats as possible. For dorks like me it's all about learning about the Ethereum ecosystem.

But for most people they just want to farm cats and make a profit. This may sound boring until you realize that a) you're playing with real money and b) this is the wild west of digital markets so anything can happen. I don't care if you're an Economics professor or a Wall Street trader or a 13 year old with way too much free time and Mountain Dew - this market is definitely challenging in new and crazy ways all of the time.

And that's kindof cool :-)

(Almost) Every Action You Initiate Has A Financial Cost

Pretty much everything you do in this app will cause MetaMask (your Ether wallet) to display a transaction confirmation popup. That's because your kitty lives on the blockchain to a large extent. And you have to spend at least a little Ether (or sometimes very much) to change anything on the blockchain.

I learned this lesson when I offered one of my cats for siring. I first had to create a CryptoKittiesCore contract on the blockchain that had no primary cost but did include a transaction fee (called gas in the Ethereum world). These gas costs are the incentive that the Ethereum miners have to process transactions.

I then changed my mind 5 minutes later and decided to cancel my siring offer. Well, that worked the same way - no primary costs, but I had to pay a gas cost. In the end, I spent a total of $3.31 in processing fees to make and change my mind.

Don't Use Much Money

Remember the gonzo crazy thing I mentioned earlier? Like I said before, this is fake money buying fake collectibles, and the CryptoKitties system could collapse overnight in hundreds of amazing and bizarre ways that no one could ever foresee.

Also, the price of Ether is incredibly volatile these days. The value has more than doubled in the last month, and there's nothing saying that it won't crash any time soon. Also, did I mention this was fake money?

Finally, I really, really, REALLY don't like that I can only interact with the CryptoKitties system using an Ethereum wallet that runs within a web browser instance. Don't get me wrong - I really like MetaMask. It's easy to install, works on multiple browsers and has a great interface. Heck, it even makes it really easy to buy Ether and automatically have it added to your wallet. And of course, it would be really hard to use a web-based dApp without some sort of wallet built into your web browser.

The part I don't like is that I'm exposing my Ethereum wallet to every single web site that I visit and every other browser plugin that I have installed. This is a huge threat and it's only a matter of time before some vulnerability in the plugin or a related browser will cause some people to lose money.

So I guess what I'm saying is that it doesn't make a lot of sense to play around with more money than you feel comfortable losing very suddenly and unpredictably. My philosophy is that I'm comfortable "playing" with the amount of money that I would spend on a good technical book. Then if I lose it all I can view it as an educational expense.

The Price Listed In The CryptoKitties App Isn't What You Pay

This is where things got very, very confusing.

Yesterday I wanted to hire the siring services of another cat so that my cat could have a kitten. I found a few cats that were advertising their stud services for 0.0049 Ether. I have 0.015 Ether. So basically it will cost me 33% of what I possess, right?

I then initiate the breeding process (ugh how else could I say that) and MetaMask tells me that this transaction will cost 0.013 Ether plus 0.006 Ether in gas costs for a total of 0.019 Ether.

So for those of you keeping track at home:

Table 1: Siring Costs
Item Cost in Ether
Stud services 0.0049
Gas 0.0060
??? 0.0081
TOTAL 0.0190

0.019 Ether (2 Ether pennies?) is a lot more (4 times more) than the half of 1 Ether penny that I thought I was spending. Heck, the price that is listed on the site is actually the smallest cost in the entire transaction!

The first question you may ask now is who is right, the CryptoKitties site or MetaMask? The answer is simple - always defer to MetaMask. MetaMask is asking you for a confirmation of a transaction that will be added to the blockchain, which means that money will be moved.

The blockchain is the system of record, and MetaMask is the authoritative tool for editing that system of record. The CryptoKitties site is neither of these things, and shouldn't be used as a way of calculating total costs.

So what are the other charges? Let's look at the gas costs first. Remember, gas it the incentive that miners have to process transactions. In the Ethereum system, this price you pay per unit of gas is proportional to the amount of activity on the network. So more concurrent transactions on the blockchain means higher costs, and things are very busy right now. 3

The CryptoKitties Site Charges Fees

This brings us to the mysterious line item in the Table 1 above. This is the amount that CryptoKitties charges to process the transaction. For now let's call this the app fee.

How is this calculated? Well I went on a message board and apparently this is broken down like this:

(Fixed Cost + ((Size / gas price) / 1000000000))

So what are all of the fixed costs and sizes for each kind of event (e.g. siring or bidding)? Well, I haven't been able to find that yet, but if this becomes more than a minor hobby for me I may need to create a spreadsheet.

It Doesn't Make Sense To Use The System When The Network Is Busy

Remember, when the network is busy you have to pay a higher gas price to ensure that your transaction is processed in a timely way. This not only affects the transaction fees that you pay but also the app fee amount that CryptoKitties charges.

It's therefore advantageous to wait until the gas price is low before initiating any transactions. Also A good rule of thumb that I've heard is that you should pay 2 more gwei than the SafeLow price on the ETH Gas Station.

CryptoKitties Isn't Fully Decentralized (Whatever That Means)

A big, theoretical promise of building decentralized apps on the blockchain is that we will no longer have to live with the calf-cow model of digital services. We will no longer have to rely on large, amoral companies to do things like manage user profiles, store data or authenticate people. We will have P2P and the blockchain and everything will be decentralized and democratized. (Digital) proletarians of all countries, unite!

Of course the modern world is very, very far away from this ideal pipe dream. We therefore still need some cows, just hopefully smaller ones :-).

So how big is the CryptoKitties cow? Well, there's actually an article on it:

The way I read this is that the site and the algorithm used to generate your kitty's genome is proprietary. Pretty much everything else exists on the blockchain.

This is a nice high-level explanation, but I still wonder what would happen to their customers and partners if the site were to disappear for some reason. For example:

  • Is it possible to know what your cat looks like without relying upon the CryptoKitties web site? Is the algorithm that converts my kitty's 256-bit genome into an adorable picture proprietary?
  • How do they ensure that people can't create counterfeit cats? Is this also proprietary to their system?


I'm really glad that I've made a small investment of time and money into the CryptoKitties system. I've learned a ton and had a lot of fun to boot. If you have any interest in where cutting edge technology, economics, and business concepts intersect then I highly recommend that you also do the same.



Or as my very astute wife likes to put it, "you bought something fake with fake money that you bought with actual money." :-)


This may sound like a sarcastic joke but it isn't. Most Ethereum dApps disappear due to malicious actions before they even get started.


If you want more information on how busy the system is and how much you should be paying for gas checkout the ETH Gas Station site.

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