1 Introduction
Blockchain, emerged as the underlying supporting technology for Bitcoin [ 1 ], is a stagger ledger system providing non-tampering and traceability functionalities. Ethereum [ 2 ], besides known as the blockchain 2.0 platform, far adds supports for bright contracts, which are programs that can be stored and executed on the blockchain system [ 3 ]. Developers can use ache contracts to create diverse decentralized applications, particularly games. Blockchain games are considered to have alone advantages over traditional on-line games in that their gambling data and logic are transparently stored and executed on blockchains [ 4 ]. These advantages particularly suit games with in-game payment and gamble mechanisms, for example, gamble, which frequently suffered from trust issues in traditional on-line environment. As a result, current designs of blockchain games chiefly revolve around the generation, possession, and deal of virtual assets [ 5 ]. Cryptokitties is a blockchain game released on Ethereum in late November 2017. Players can own, trade, and create virtual kitties, represented by non-fungible tokens meeting the ERC-721 nominal standard in the game. The attributes and transactions of kitties are recorded in the Ethereum blockchain. once released, CryptoKitties soon gained massive popularity that its transactions accounted for more than 10 % of the integral Ethereum traffic in early December 2017 [ 6 ].
Reading: CryptoKitties Transaction Network Analysis: The Rise and Fall of the First Blockchain Game Mania
however, Min et alabama. [ 4 ] claimed that most of the current blockchain games lack playability. possible reasons include that current blockchain platforms restrict developers from implementing complex game functions, stream developers are paying insufficient attention to the players ’ gaming experience, and lack a competitive market in the blockchain plot industry. not amazingly, the popularity of CryptoKitties only lasted for a short period, besides. In this study, we aim to amply unveil the collective user behaviors in the game and the reasons leading to the game ’ second rapid lift and fall by analyzing blockchain transaction records. specifically, we inaugural construct a kitten possession transfer network and investigate the net structural changes over fourth dimension. then, we conjecture and verify the potential reasons for the rapid changes in gaming popularity from four perspectives : the add and demand of kitties, the profitableness in the game, the inequality of players ’ wealth, and the limitations of blockchain systems. Based on our observations, we pinpoint the deficiencies in the design of CryptoKitties and provide suggestions for further development of blockchain games. Network psychoanalysis methods have been applied to cryptocurrency transaction records in many previous works. Chen et alabama. [ 7 ] constructed three graph with ether transfer, contract initiation, and narrow invocation, found a power-law degree distribution, and revealed anomalies in these graphs. Somin et alabama. [ 8 ] besides found a power-law degree distribution in the ERC20 token transfer network. Guo et alabama. [ 9 ] far revealed a bow tie structure in the Ethereum transaction network. Except for the Ethereum blockchain, exchangeable methods have besides been used to analyze transactions on other blockchains, such as EOSIO [ 10 ]. The lie of this paper is organized as follows. CryptoKitties ’ bet on rules are introduced in part 2. In section 3, we construct the pool ownership transfer network and specify network morphologic properties. In department 4, we divide the advance of the game into four stages and examine the changes of network parameters in different stages. We will discuss the reasons for the rapid change in the popularity of CryptoKitties in section 5. section 6 concludes the analyze and provides suggestions for the far development of blockchain games .
2 Gaming Rules
As shown in table 1, the CryptoKitties game has five bright contracts : the Core sign, GeneScience contract, Offers contract, SalesAuction contract, and SiringAuction contract. The names of these contracts could be found on Etherscan [ 11 ]. Based on these contracts, players can trade or transfer kitties with other players and breed newfangled kitties. table 1
TABLE 1. CryptoKitties ’ second fresh contracts. There are three ways to trade or transfer a pot. ( 1 ) Using the SalesAuction abridge. The seller lists a pot for sale with an initial price, a concluding price, and a price change period to the SalesAuction contract. The initial price is normally higher than the final examination price. After the auction begins, the kitty price will change linearly from the initial price to the concluding price at a ceaseless rate during the price change menstruation. The price will not change after this time period. Unless command by a buyer or canceled by the seller, the pot will remain in the SalesAuction compress. Upon receiving a bid, the SalesAuction contract will send the kitten to the buyer and transfer the requital to the seller. The game publisher besides sells 0-generation kitties to players in this way. ( 2 ) Using the Core narrow. A player can either call the transfer function to transfer his kitten to another player or the approve function to allow other players to transfer his pot. authorized players can call transfer from officiate to transfer other players ’ kitties. Transferring a pot in this way does not inevitably mean that the musician is trading the kitty but can besides be sending a kitten as a endow to a friend. ( 3 ) Using the Offers contract. In this way, the buyer initiates a request to the seller and sends the buy tip to the Offers contract. If the seller accepts the request, the Offers contract will transfer the kitten to the buyer ’ mho address and send the buy fee to the seller. When deal kitties through the SalesAuction, the bet on publisher charges the sellers for 3.75 % of the conduct price as a treatment fee. lapp rate of dealing price will be charged to the buyers using the Offers contracts. When calling any officiate in each sign, the players besides need to pay gas fees to Ethereum miners through their Ethereum wallet. The flatulence tip is normally between 0.0001eth and 0.01eth. There are two ways to breed a new pool. ( 1 ) A player selects two of his own kitties as parameters and call the breed With Auto function in the Core abridge with a breeding fee. After this operation, the mother kitties ( can be randomly chosen between the two ) will become fraught for a menstruation. After this time period, a player, besides called the midwife, will call the pass parturition routine in the Core sign to give parturition to the raw kitten. The newborn kitty will be transferred to the owner of the mother pool. The engender fee will be compensated to the midwife for their Ethereum gas fees paid. ( 2 ) A player breeds with one of his own kitties and another rented from the Siring Auction contract, which lists a number of kitties owned by the lenders. A midwife is besides needed in this case. When a pool is rented out through the Siring Auction contract, the crippled publisher will charge the lender 3.75 % of the rent as a handling tip. The breeding fee varied over time ( see Figure 1 ). It was set to 0.002eth at the game ’ randomness turn. however, due to the congestion of the Ethereum network resulting from the gaming transactions, the gas fee was raised. The game publisher increased the breed fee to 0.015eth and late adjusted it to 0.008eth. such alteration happened several times subsequently, but despite that, the breeding fee has been stable at 0.008eth. FIGURE 1
FIGURE 1. Changes of the breed fee .
3 Data and Methods
3.1 Blockchain Transactions
We synchronized an Ethereum parity client in broad mode and used the eth_getLogs method to extract the transactions in CryptoKitties. The transactions span from November 23, 2017, to May 19, 2020. The data involved 1,923,901 kitties, 104,517 addresses, and 5,173,521 transfer records. There are nine types of transactions ( see Table 2 ) related to the movements of kitties, including the trade, transferring, and the new give birth of kitties. Consider participation rate as the ratio of the number of addresses that take contribution in a specific action to the number of all addresses in CryptoKitties, buy kitties through the SalesAuction compress has the highest engagement rate ( 84.6 % ), indicating that most players would buy at least one pot from the official marketplace. engagement rates are besides high for breeding kitty ( 64.9 % ) and selling kitty through the SalesAuction contract ( 51.8 % ). Players showed gloomy interest in lend ( 38.1 % ) and renting kitties ( 26.6 % ). only a very humble count of players ( less than 1 % ) traded kitties through the Offers abridge. mesa 2
TABLE 2. Nine types of transactions related to the movements of kitties .
3.2 Constructing Ownership Transfer Network of Kitties
The actual ownership of the kitties lone changes when ( 1 ) the sales auction on the SalesAuction condense is fulfilled, ( 2 ) the trade through the Offers contract is fulfilled, and ( 3 ) kitties are transferred directly using functions in the Core sign. consequently, We construct the pot ownership transmit network G= ( V, E ), where V is the set of addresses belong to kitty owners, including the game publisher and players, who have the actual ownership of kitties, and E is the set of send edges representing the actual ownership changes. The directed edges e= ( uranium, volt, t ) are temporal role, where uracil represents the address of pool ’ s previous owner, vanadium represents the address of kitten ’ s new owner, and deoxythymidine monophosphate represents the meter when the ownership change occurred. The network contains 104,514 nodes and 1,304,525 edges. We further use three days as the window size and construct a series of temporal networks G= ( G1, G2, … ), where Gt is the network in clock window t .
3.3 Network Structural Properties
We use the average degree, non-zero in-/out-degree proportion, Gini coefficient of in-, out-, and full degrees, modal clustering coefficient, concentration, reciprocity, and assortativity to describe the structural properties of the network. The average degree k¯=2M/N represents the average issue of kitties transferred in and out of the addresses, where M is the number of edges and N is the number of nodes in the worldly network. The non-zero in-/out-degree proportion α=Nout > 0/Nin > 0 is defined as the proportion of the count of nodes with an out-degree greater than zero ( Nout > 0 ) to those with an in-degree greater than zero ( Nin > 0 ) in the temporal role network. It can besides be considered as the ratio of the total of sellers to buyers in the game. The Gini coefficient Gk of the total degree kilobyte of all nodes in the temporal net reflects the gap between the players ’ action in the count of kitties transferred in and out of the address, i.e. ,Gk=1N(N+1−2∑i=1N(N+1−i)ki∑i=1Nki), where ki is the degree of lymph node i indexed in non-decreasing decree ( ki≤ki+1 ) and N is the number of nodes in the net. The Gini coefficients for the in-degrees Gkin and out-degrees Gkout of all nodes can be defined besides. The average bunch coefficient deoxycytidine monophosphate is used to measure the bunch degree of the net, which is defined asc=1N∑v∈VTvkv(kv−1)−2kvr, where television is the number of direct triangles passing through the node five, kilovolt is the degree of node vanadium, and kvr is the number of bidirectional edges of node v. Multiple edges between uracil and five are considered as one even with the lapp t in this case. high average clustering coefficient means that players interact close with other players. Network concentration d=M/ ( N ( N−1 ) ) describes the assign of the electric potential connections in the network that are actual connections. Again, multiple edges between uracil and volt are considered as one evening with the same t in this font. The reciprocity ρ=2Mu/M describes the ratio of the number of edges pointing in both directions to the sum count of edges in the network, where Mu is the phone number of adrift edges in the network. High reciprocity means that the kinship between addresses is relatively potent, and the owners of these addresses are likely to know each other. multiple edges between uranium and v are considered as one even with the like triiodothyronine in this case. The degree assortativity coefficient r measures the similarity of connections in the network with regard to the node degree :r=∑ij(Aij−kikj/2M)kikj∑ij(kiδij−kikj/2M)kikj, where Aij is an element in the adjacency matrix, qi and kj are the degrees of node one and joule, and δij is the Kronecker affair. The direction of edge is ignored and multiple edges are considered in the calculation .
4 Collective Behaviors of CryptoKitties Players
4.1 The Four Stages of Game Progress
Using the numbers of day by day addresses related to CryptoKitties transactions, the game can be divided into four stages : the primer, the emanation, the fall, and the repose, as shown in Figure 2. 1. The flat coat : The game was released on November 23, 2017. There were not many players before December 2, 2017. 2. The raise : A big numeral of players entered the crippled since December 2, 2017. The game popularity quickly increased before reaching a extremum on December 10. 3. The drop : Since then, the popularity has dropped aggressively. At the beginning of 2018, the game ’ sulfur popularity is less than 10 % of its point. 4. The peace : After January 15, 2018, the popularity stabilized into a long-run slow down vogue. trope 3 shows four snapshots of the network in each of the stages. The net size shrinks apparently over meter. FIGURE 2
FIGURE 2. Four stages of the game. The three dotted lines match to December 1, 2017, December 10, 2017, and January 15, 2018, respectively. FIGURE 3
FIGURE 3. Visualizations of typical networks in every stage. Nodes in the net are filtered by out-degree. (A) There aren ’ t many early players in stage 1. (B) The network contains a large numeral of nodes in stage 2. (C) The network shrinks in degree 3. (D) merely long-run players are left in stage 4 .
4.2 Evolution of the Network Structure
The evolution of network geomorphologic properties in the four stages are shown in Figure 4. In the first phase, the Gini coefficient of out-degrees decreased on the spur of the moment. This is because about all 0-generation kitties were transferred from the game publisher ’ randomness addresses to the players in the first few days. soon after that, players began to breed new kitties and sell them to each early. The decreases in average degree, network concentration, and average cluster coefficient result from early on players entering the game and expanding the net. interim, the assortativity coefficient stayed damaging because low-degree players tended to trade with high-degree players, who are the game publisher. FIGURE 4
FIGURE 4. evolution of the net structural properties over time. (A) The average academic degree, (B) the non-zero in-/out-degree ratio, (C) the Gini coefficients of in-, out-, and sum degrees, (D) the average bunch coefficient, (E) network concentration, (F) reciprocity, and (G) assortativity. Dotted lines separates the four stages. The labels on the x-axis present the middle date of prison term windows. The x-axis are re-scaled to better illustrate the argument dynamics in stages 1, 2 and 3. In the second stage, the network concentration stayed low due to the large issue of players entering the game. The degree assortativity coefficient increased to zero, meaning that low-activity players tended to transfer kitties among themselves rather than trading with high-activity players. In the third stage, the non-zero in-/out-degree ratio maintained an up vogue, indicating that the proportion of sellers to buyers was increasing, and market contest was intensifying. The Gini coefficient of out-degrees decreased gently, indicating that flush the seller/buyer proportion increased, the opening between sales volume among sellers was narrowing. however, in-degrees ’ Gini coefficient went astir on the spur of the moment. The anomalous data period around December 23, 2017, was caused by an exceptionally large number of transactions made by a handful of addresses. In the fourth stage, the increasing average degree and reciprocity indicate that the players left in the games were actively trading with each other. The Gini coefficients all maintained an upward tendency, indicating a large break shape in these players : some big players were gradually dominating the game. note that the average degree, Gini coefficients, and reciprocality abruptly increased in June 2019. We found that they were caused by the launch of Wrapped Cryptokitties ( WCK ), which is an ERC-20 token contract, enabling players to exchange unwanted ERC-721 kitties for WCK and use WCK to exchange other kitties. The successor of a large total of ERC-721 kitties with WCK resulted in a sudden fluctuation in the network structure .
4.3 Changes in the Kitty Ownership Transferring Methods
There are three ways to transfer the ownership of kitties : through the SalesAuction, Offers, or Core contracts. The changes in the proportions of the three methods over time are shown in Figure 5. In the early on days of the game, the ownership transfer of kitties was chiefly realized through the SalesAuction contract. late, the proportion of transferring kitties with the method in Core contract gradually increased. After April 2019, this method had become the main way of transferring kitten ownerships. The act of kitties transferred through the Offers contract was always little. FIGURE 5
FIGURE 5. The change in proportion of three methods to transfer the kitties. cost was the independent reason for this change. Players tend to transfer kitties at a lower cost. When buying and selling kitties through the SalesAuction and Offers contracts, players need to pay a transaction fee to the game publisher, normally 3.75 % of the transaction sum. Using the transmit method acting in the Core abridge, in contrast, merely requires a gas tip payment. Therefore, some third-party trade platforms emerged to help players trade kitties, charging fewer transaction fees. For model, the transaction fee charged by the OpenSea deal platform is only 2.5 % .
5 Reasons for the Rise and Fall of CryptoKitties
5.1 Reasons for the Explosive Growth of Game Popularity
On December 2, 2017, the pot with ID 1 was sold for 247eth, i.e., more than US $ 100,000 [ 12 ]. This message spread quickly on the Internet, generating a large amount of attentions. design 6 shows the Google course index of CryptoKitties and count of daily addresses related to CryptoKitties transactions. Kitties traded at extremely high prices will undoubtedly attract media care and bring many newfangled players to the game. The increase attention from Internet users finally led to the explosive growth of the bet on ’ south popularity. We can not rule out the possibility that the plot publisher measuredly made the newsworthiness that a limited pool has being sold at an highly high price. In fact, about all transactions with an sum greater than 100eth occurred in early on December 2017, which corresponds precisely to the ascend stage of the game. however, despite of the causal agent, media exposure had indeed increased the game popularity significantly. FIGURE 6
FIGURE 6. Google Trends of CryptoKitties and the numbers of daily active addresses. Cryptocurrencies, such as Bitcoin, show a positive correlation coefficient between their prices and the sizes of the drug user groups [ 13 – 15 ]. The kitties in the game are ERC-721 token, and consequently, the lapp rule applies. On the one hand, the expansion of the musician community has increased the requirement for pool tokens and promoted the rise of kitten price. On the early hand, the increase in kitten price attracted more players to join the community. finally, the submission of a large number of players into the game has led to a surge in demand for kitties, hence the kitten price ( see Figure 7 ). The mean price of kitties in each day is significantly higher than the median price because a belittled issue of kitties were sold at importantly higher prices than median. FIGURE 7
FIGURE 7. Mean and medial prices of the kitties sold in each day .
5.2 Reasons for the Rapid Fading of Game Popularity
The rapid growth of bet on popularity only lasted less than ten days. Since then, the number of players has dropped precipitously. Lee et alabama. [ 16 ] noted that users ’ playing behaviors in CryptoKitties are affected by bad and enjoyable factors. here, we propose four specific reasons that could account for the rapid decline in game popularity : the out-of-balance of the provision and demand of kitties ; the loss of profit in kitten trade ; the increasing gap between the rich and poor players, and the limitations of blockchain systems .
5.2.1 The out of Supply and Demand Balance
The bombastic numeral of players poured in during the explosive growth degree bred a big total of kitties in a identical short time. Since December 4, 2017, the count of new kitten listings has significantly exceeded the total of kitties sold every day, resulting in a rapid increase in the number of kitties left on sale, i.e., stock armory ( see Figure 8A ). The kitty market has become a buyer ’ second market, and the contest has intensified. The proportion of a successful sale for kitties listed on each day besides decreased ( see Figure 8B ), and the dollar volume time, i.e., the average time interval between kitty list and trade close become longer ( see Figure 8C ). FIGURE 8
FIGURE 8. The supply and necessitate of kitties in the commercialize. (A) The numbers of new pool listings, kitties sold, and kitties on sale in the marketplace every day. (B) The ratio of successful sale for kitties listed on each day. (C) Turnover time, i.e., the average time interval between pool listing and barter close for kitties listed on each day. Dotted lines separates the stagecoach 1, 2 and 3.
5.2.2 The Loss of Profit in Kitty Trading
Buchholz et aluminum. [ 17 ] pointed out that the value of cryptocurrencies has no benchmark but strictly depend on the issue and demand in the grocery store. As the add of kitties significantly overwhelmed the demand, the price of kitties dropped significantly. profit is an important motivation to encourage the players to stay in the crippled. If their gross from selling kitties becomes lower than the costs, the players ’ exuberance will decline or evening disappear. Teoretically, suppose a actor uses two of his own kitties to breed a new pot and sell it at the medial kitten monetary value ( excluding the 0-generation kitties ) through the SalesAuction abridge on the lapp day. The median cost of breeding and selling a kitty in one day can be written asc=fbreed+gbreed+gsell, where fbreed is the average education fee, gbreed is the average flatulence fee for kitten breeding, and gsell is the median flatulence fee to sell a kitty through SalesAuction abridge on a particular day. The profit of a pool sale on the lapp day can be written asp=0.9625×vmedian−c, where vmedian is the median price of kitties ( excluding 0-generation kitties ) sold on that day. The seller can alone receive 96.25 % of the share price after deducting the 3.75 % handling fee received by the game publisher. number 9A shows that the cost break-down for breeding and selling increase sharply in stage 2. Among all the costs, the breeding tip is the highest, followed by the miner ’ s fee for the sell mathematical process, and the miner ’ s tip for the breed operation is the lowest. figure 9B shows that starting from December 13, 2017, the average profit for a actor to breed and sell a kitten became negative, indicating that the musician may lose money when playing the game. FIGURE 9
FIGURE 9. The loss of profit in pot sales. (A) The average engender fee, accelerator fee for breed, and gas fee for selling a kitty through SalesAuction abridge on each sidereal day. (B) The gross ( median price of kitties ), price, and net income for breeding and selling a pool on each day. Dotted lines separates the stage 1, 2 and 3. The actual in-game education and sale may not happen on the lapp day. For every kitten sold, the seller ’ s actual net income can be evaluated by the deviation between the education or learning cost and sell gross. here, we besides estimate the actual net income of kitties sold each day. For the kitty sold for the first meter, the seller ’ second profit can be written asp1=0.9625×v−fbreed−gbreed−gsell−r−grent, where vanadium is the price at which the pool is sold, fbreed is the breeding fee, gbreed is the boast fee for pot education, and gsell is the natural gas fee to sell the pool. If the actor rents another player ’ sulfur kitty, he has to pay the rent gas constant and boast tip grent. The seller can lone receive 96.25 % of the consider price after deducting the 3.75 % handling fee for the game publisher. For the kitties that are bought from others and resold, the seller ’ sulfur profit can be written asp2=0.9625×vsold−vpurchase−gpurchase−glisting, where vsold is the sold price, vpurchase is the leverage monetary value, gpurchase and glisting are the gas fees paid in purchasing and selling the kitten. The seller can merely receive 96.25 % of the manage price after deducting the 3.75 % handling fee for the game publisher. design 10 shows the probability of generating a positive profit by selling kitties each sidereal day. After December 6, 2017, this probability for kitty resales became less than 50 %. After December 13, 2017, this probability for selling self-bred kitties became less than 50 %. Whether the player sells kitties bred by self or previously purchased, there is a great chance of losing money. FIGURE 10
FIGURE 10. The probability of generating positive profit in selling a pot each day. Dotted lines separates the degree 1, 2 and 3 .
5.2.3 The Increasing Gap Between the Rich and Poor
Players receive gross from selling and lending kitties. In the foremost stagecoach of the game, the Gini coefficient of casual gross from selling and leasing increased significantly ( see Figure 11A ), and that of the accumulative gross for all the addresses besides increased importantly ( see Figure 11B ). After entering the third stage, although the Gini coefficient of the gross earned by players from selling and renting fluctuated, they all remained at a relatively high floor ( greater than 0.6 ). The Gini coefficient of roll up tax income stayed at a high level ( greater than 0.8 ). Since 0-generation kitties were chiefly sold by game publisher, these sales were not considered when counting the gross of players. Our results show that the gap between the rich and poor in the crippled expanded. A few players earned most of the money from the game, while most can only get very little income, if any. The increasing col in the gross has caused most players ’ gaming experience to deteriorate, and they gradually withdrew from the game. FIGURE 11
FIGURE 11. Gini coefficients of (A) day by day betray and lending gross and (B) the roll up gross from pot sale and renting for all the addresses. Dotted lines separates the stagecoach 1, 2 and 3. not only the revenues, pool ownerships were besides gradually concentrated to a few players. The Gini coefficient of the count of kitties owned by all addresses at each stage is shown in Figure 12. When counting the total of kitties belong to an address, unsold kitties in the SalesAuction sign belong to the seller, and unrented kitties in the SiringAuction sign belong to the lender. In the beginning and second gear stages, many newly players entered the crippled, all making buying, and the Gini coefficient gradually decreased. however, as the count of raw players decreased and existing players depart, the Gini coefficient rose in the one-third stage and kept rising in the fourth stagecoach. As of April 2020, the Gini coefficient of kitties with addresses has exceeded 0.8. At this time, the resources in CryptoKitties became highly concentrated. FIGURE 12
FIGURE 12. The Gini coefficient of kitties owned by all addresses. Dotted lines separates the four stages. The x-axis are re-scaled to better illustrate the parameter dynamics in stages 1, 2 and 3 .
5.2.4 Limitations of Blockchain Systems
The monetary value of performing operations on a public blockchain arrangement is highly volatile due to the mentally ill monetary value of cryptocurrencies, resulting in it difficult to control the cost of the applications deployed on the blockchain. As CryptoKitties was deployed on Ethereum, the cost of playing the game ( including the costs of buy, breed, and renting kitties, vitamin a well as the fees paid to Ethereum miners ) has risen significantly due to the rapid wax of Ether price in the third stage. Ether monetary value increased from US $ 451 on December 10, 2017, to US $ 1,322 on January 10, 2018 ( see Figure 13 ), resulting in a meaning increase in the cost of playing the game, raising the bars for new players entering the game. FIGURE 13
FIGURE 13. The Ether price. Dotted lines separates the stagecoach 1, 2 and 3. In addition to the cryptocurrency price, other potential limitations of blockchain systems include the unnecessary gas cost by ailing designed smart contracts and the depleted system throughput ( measured in transaction per second base, TPS ). Under-optimized smart contracts will consume more gas than necessity [ 18 ], making it more expensive for users to play games. Chen et alabama. [ 19, 20 ] studied the flatulence cost mechanism of Ethereum and proposed a way to optimize smart contracts through analyzing bytecodes, potentially reducing the bet on costs. The low throughput of Ethereum [ 21 ] has rendered that coincident operations by many users are not feasible. once besides many players have joined the game, the time needed to validate operations in the game takes excessively long, consequently sabotaging the players ‘ bet on experiences .
6 Conclusion
This paper is the first to fully unveil the exploiter activities in the once most popular blockchain game CryptoKitties and identify the reasons for its rise and fall. Based on the number of addresses associated with the game every day, we divide the process of CryptoKitties into four stages : the fuse, the lift, the drop, and the repose. We extracted all the five million pool transactions from the Ethereum blockchain and constructed the kitty possession transfer network for characterizing the exploiter behaviors. We found that a big numeral of players flooded in the bet on in the early days but cursorily withdrew later, and a few big players gradually took manipulate of the crippled. We found that the public attention draw by the message that a special kitty was sold at an extremely high price finally led to the explosive growth of bet on popularity. For the rapid worsen of the popularity, reasons including 1 ) the glut of game props, i, the kitties, 2 ) the loss of profit in the game prop deal, 3 ) the increasing opening between the wealth distribution among the players, and 4 ) the limitations of blockchain are accounted for. Drawing from these observations, we advise on the design of future blockchain games as follows. 1. Design a reasonable prop up output mechanism to keep a balance between add and requirement. 2. Provide a mechanism for adjusting player income to prevent players losing money in prop up trade with a high probability. 3. Design a mechanism to narrow down the break between the ample and poor and prevent the tax income from being gained by only a few players. 4. To amply consider the limitations of blockchain systems in the game plan .
Data Availability Statement
Publicly available datasets were analyzed in this study. This datum can be found here : hypertext transfer protocol : //github.com/jiangxjcn/Cryptokitties-analysis.git .
Author Contributions
Both authors designed the study and wrote the composition. XJJ conducted data analysis .
Funding
This work is supported by CityU Start-up Grant for New Faculty ( No. 7200649 ) and CityU Strategic Research Grant ( No. 11503620 ) .
Conflict of Interest
The authors declare that the research was conducted in the absence of any commercial or fiscal relationships that could be construed as a potential conflict of interest .
Acknowledgments
We thank Si-Hao Liu and Ying-Hao Zhang for their suggestions on the revision of this article .
References
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