Improved Balance in Multiplayer Online Battle Arena Games by Chailong Huang Athesis submittedto the Department ofComputerScience inconformity withtherequirements for thedegree ofMaster ofScience Bishop’s University Sherbrooke, Quebec, Canada March 2018 Copyright Chailong Huang, 2018 Abstract The Multiplayer Online Battle Arena (MOBA) game is a popular type for its competition between players. Due to the high complexity, balance is the most important factor to secure a fair competitive environment. The common way to achieve dynamic data balance is by constant updates. The traditional method of finding unbalanced factors in a MOBA game like DOTA2 is mostly based on professional tournaments, which is a small minority of all the games and not real-time. We develop in this thesis an evaluation system for the DOTA2 based on big data with clustering analysis, neural networks, and a small-scale data collection as a sample. We then provide an ideal matching system based on the Elo rating system and an evaluation system to encourage players to try more different heroes for a diversified game environment and more data supply, which makes for a virtuous circle within theevaluation system. i Directory 1 Introduction................................................................................................................1 2 MOBAGames Overview...........................................................................................3 2.1Development Path ofMOBAGames...................................................................3 2.2RepresentativeofMOBAGames.........................................................................4 2.3Related Properties ofDOTA2..............................................................................6 3 GameBalance Overview............................................................................................9 3.1StaticData Balance............................................................................................10 3.2DynamicData Balance.......................................................................................13 3.3Matching System Balance..................................................................................15 4 Preliminaries.............................................................................................................16 4.1DOTA2 Matching System..................................................................................16 4.2K-Means ClusterAnalysis..................................................................................18 4.3Artificial Neural Network...................................................................................18 5 Balance Implementation in DOTA2.........................................................................21 5.1Evaluation System fortheDynamic Data Balance ofHeroes............................21 5.2Ideal Matching System Design Based ontheElo Rating System......................33 6 Conclusions..............................................................................................................38 References....................................................................................................................40 Elo PercentageExpectancy Table................................................................................42 ii Chapter1.Introduction Chapter 1 Introduction The explosive development of the Internet has brought great convenience to people, and also made leisure and entertainment style much more diversified. Electronic games [1], especially e-sports games, have become an important part of people's lives. With the increasingly diversified social life and the gradual emancipation of people's minds, electronic games are becoming more and more mainstream, especially among young people. The game industry has also flourished, more and more excellent games are coming out.As a common way of entertainment in daily life, the electronic game is a good help for people to eliminate fatigue and reduce the mental pressure of studying and working. Some healthy games can even help children grow up happily in an educational way [2]. Research shows that games have a good effect on the development of the brain, especially for minors. An electronic game is software, which needs hardware equipment with certain performance to provide the operating environment. With the substantial increase in hardware performance and people’s desire to pursue better entertainment, various types of high-quality games are coming to people’s daily life. Multiplayer Online Battle Arena (MOBA) games [3] are very popular among young people because of their interesting and playful features. The reason why there are so many MOBA game lovers is the competition in all kinds of areas such as operation, strategy, teamwork. Thebasis of thiscompetitivepleasure lies in its balance. DOTA (Defense of the Ancient) is the first independent MOBA game. As a classic game with a 15-year history, it’s still very popular as the second generation DOTA2. Witnessing its enduring popularity, more and more companies have seen the business opportunities, so a batch of similar MOBAgames came out,“LeagueOf Legends” from Riot Games, “Heroes of the Storm” from the famous Blizzard Entertainment, “Heroes of Newerth” from S2 Games are all excellent MOBA games. Even though they are not as balanced as DOTA, they still havea large numberof players. Chapter1.Introduction 2 Success and failure always exist simultaneously, so not all games are as excellent as the ones mentioned above. In China there are even more MOBA games, but most of them are commonly criticized for their low quality, unbalanced setting, even plagiarism. Game design is actually a process of producing artwork: beside creativity and inspiration, exquisite workmanship is also required. Balance is the workmanship of games. It is even more important in a competitive MOBA game. An imbalanced game cannot guarantee the loyalty of the fans; players will get bored easily if they only have a few options to win a game. Thus a deep understanding of thebalance of the game as well as the way to achieve it are both necessary for a MOBA game. With the analysis of MOBA game and data balance, this thesis develops a new method to achieve a better implementation of dynamic balance in DOTA2, and then an ideal matching system is designed as an improvement over theoriginal one. In this thesis Chapter 2 focused on the overview of an emerging game type called MOBA (Multiplayer Online Battle Arena), with the representative work DOTA2 (by Valve Corporation). In Chapter 3 we show that because of MOBA game’s complexity, balance is the most important purpose for designers from the design process (static balance) to an on-going concern through new patches (dynamic balance). Most companies like Valve are trying to evaluate the imbalanced factors based on players reports and game situations in professional tournaments. The former only reflects the most prominent problems, the later only include professional players as sample, ignoring thousands million ordinary players around the world. In Chapter 4 preliminaries about DOTA2 rank/ matching system, K-Means cluster analysis and BP-Neural Network are introduced for further research. The main contribution of this thesis is in Chapter 5, where a new method is developed to achieve a better implementation of dynamic balance, with small-scale data collection as a sample.As a multiplayer online game, a fair matching system also plays an important role in game balance. Based on DOTA2 original rank/matching system (which uses the same rank system based on Elo ratings as “League of Legends”), we design an ideal algorithm for the matching system. Finally we come up with an improvement on the rank/matching system based on the analysis of dynamic data balance.Finally potential problem and further research are discussed inChapter 6. Chapter 2 MOBA Games Overview MOBA is the abbreviation of Mutiplayer Online Battle Arena games, also called Action Real-time Strategy Games (Action RTS, ARTS), or DOTA-like Games, which is a subclass of Real-time Strategy Games. In a MOBAgame, there are no buildings, population, resources, arms training, technology tree, or unit organization, which are all common in traditional RTS games. Players in MOBA games are usually divided into two camps, five versus five by fighting for more gold to buy items, and experience to level up, which can all strengthen the players’units. The ultimate goal is to destroy a certain building of the other side. Unlike most traditional hard-core RTS games such as “Warcraft III: The Frozen Throne” and “Star Craft”, MOBA game player usually controls one character only called “hero”,which has specific abilitiesand slotsto equip with items. Compared with traditional RTS game, MOBAgames are more entertaining, so the difficulty of the operation is designed to be acceptable for most of the average players. Not deliberately requiring any high level of operation and mental strength makes MOBAgames more universal, and easier to start. Beside, most MOBA games are free games, which is another low threshold for a large number of players. 2.1DevelopmentPath ofMOBAGames Origin In 1998, Blizzard Entertainment released the classic RTS game “Star Craft”, which is the first time that Blizzard bound a map editor with a game, which allows all the players to edit their own map. Among all custom maps, the one named “Aeon of Strife” from an unknown player became originator ofall MOBAgames. Chapter2MOBAGameOverview 4 Development In 2002, “the conscience of gaming industry” Blizzard Entertainment again released the sequel of “Warcraft” series “Warcraft III: Reign of Chaos”. This legendary game soon became the hottest topic for every player around the world. As before, a map editor was released with the game itself, which threw players once again in the madness of designing custom maps. In a short time, a group of mapdesigner got together and planted theseed ofDOTA, themilestoneofMOBAgames. The warcraft-version “Aeon of Strife” first came out, followed by “Valley of Dissent” and “Defense of the Ancient”. Finally, “DOTA All-Star” became the ultimate DOTA map, with continuous updates tofix bugs and adjust balance. Sincethen, MOBAevolved into areal gametype. Prosperity The fantastic gameplay attracted countless crazy players in a very short time. Tens of unique heroes, various items, fine operability, imaginative tactics, and of course the constantly improved balance, all these advantages allowed DOTAto sweep the world in a few months.Asia, Europe, South and North America were suddenly full of DOTAplayers and lovers. While at that time “Warcraft III” including DOTA could only be played on local area network, LAN Battle platform became another business opportunity. With the heat of DOTA, many battle platforms appeared, such as GG (Good Game) and VS. More and more players gave up on all kind of custom maps such as 3C, RPG (Role-playing game) maps and even Warcraft III itself, to became DOTA fans. It was also at that time that the huge number of players attracted other game companies, which tried to share this MOBAcake.As a result, some excellent MOBA game like “Smite” and “League Of Legends” came out, with great success and huge profit. Based onthese success precedents, even moreMOBAgames kept coming out. 2.2Representative ofMOBAGames DOTA2 Since DOTA came out, countless imitations followed the trend. Of course, most of them got their own features, in one way or another. Though DOTAis classic and balanced, it is just a custom map based on the Warcarft III game engine [5] after all, which is a game from 2002. With the rapid development of information technology, old game engines are destined to be eliminated because of Chapter2MOBAGameOverview 5 their shortcoming and limitations: There is a 8MB limit for Warcarft III custom maps, which means that one day inevitably no more new elements could be added into DOTA, including new heroes, abilities and items. Low image quality was also intolerable to players after 10 years. Last but noleast, some bugs based on the game engine itself can never be fixed in DOTA. All these problems have restricted the further development of DOTA. At the same time, new MOBA games such as “Smite” and “League Of Legends” competed for DOTA players based on their own engines and good publicity, and so kept more and more potential players away from DOTA. This phenomenon seemed to suggest that DOTAwas meant to gradually exit the stage of history. In 2008 Icefrog, “the father of DOTA” who kept updating DOTAwithout any benefits for years, finally decided to take a new step in DOTA's life, that is,make DOTA2. In 2009, Icefrog and Valve hit an agreement, starting the development and research work on DOTA2. After two years, DOTA2 came out, and immediately won the praise of players around the world. Based on Source Engine [14], DOTA2 fixed most bugs that would never be fixed in DOTA, with brand new features like skins, watch, matching, voice chat, community, and reports. Since then, DOTA2 literally became a individualgame, detached fromWarcarft III. To this day, DOTA2 still has a large number of players, with a 1.2 million highest number of online players on Steam (the platform of Valve). Also DOTA2 is the leader on professional e-sports game. In 2017, the International 7 was held in Seattle, U.S. with a more than 24 million dollar prize pool. Players who left DOTAreturned to DOTA2, which again shows the classic nature and balance of this game.As a high-quality MOBAgame, with remarkable gameplay and balance, this thesis will takeDOTA2 as an analysis template. OtherMOBAgames “League Of Legends” or LOL was developed by Riot Games, which has been acquired by the Chinese Internet giant Tencent. Besides the classic MOBA elements from DOTA, LOL also has its ownfeatures, suchas runes, talent tree, and ofcourse, brand new heroes. Looking around the world, LOL has much more players than DOTA2, mainly because of Riot’s wise development strategy that released the game with vigorous publicity in 2010-2011, during the period that players lost by DOTA have not joined the DOTA2 camp. Also, LOL is even more entertaining than DOTA2, with lower difficulty to get started. The bright color cartoon style attracted more young players as well. Objectively speaking, in game balance, LOL didn’t do as good a job as Chapter2MOBAGameOverview 6 DOTA2 did. For example, in professional games the heroes played rate (the number of heroes that have been picked in the whole tournament versus the total number of heroes) of LOL is much lower than DOTA2, that is, so many heroes in LOL are too weak to be picked and played in professional games, which means that thedesigns of theseheroes is not balanced. “Heroes of Newerth” (HON) was developed by S2 Games. It inherited DOTA's traditional play style, and has a great numberoffans in Europe andAmerica with excellent reputation. “Smite” was developed by Hi-Rez Studios. This 3D MOBA game is based on the Unreal 3 game engine. Under the epic background of the war of gods, “Smite” combines for the first time MOBA with a FPS (First Person Shooter) game. Therefore, it has a higher requirement for players’personal operating skillsand teamwork. Drawing on “Smite”’s success, Blizzard Entertainment developed and published “Overwatch” in 2016. With better game engine and images, “Overwatch” caused a huge response, and won the “Game of the Year” at the 20th annual DICE Awards (by the Academy Of Interactive Arts & Sciences) There are so many successful MOBA games. The above are just some representative cases. In general, these games all came from the idea of DOTA, combined with their own creativity such as FPS, and history or mythology background. All in all, the basis of MOBA games is the balance, which of course, got the mostsuccessful implementation inthe DOTAseries. 2.3Related Properties of DOTA2 DOTA2 is a very complicated game. This thesis will only introduce the elements that are related to ourresearch, while omittingirrelevant factors. Introductiontothemapandthewaytowin In general, every DOTA2 game has 10 players, divided into two camps. Every player needs to pick a hero to control at the beginning of the game, doing a 5 versus 5 confrontation. The two camps are respectively called Radiant and Dire with one ancient structure in each of their bases. The bases are located on each side’s high ground, with three lanes to the other side. For each side, there are two barracks (melee and range) and tree defense towers on each lane. Barracks produce three types of “creeps” (melee, range and siege)every 30 seconds who automatically attack all the enemy units Chapter2MOBAGameOverview 7 along the lane. Defense towers automatically attack enemies whenever within their range. The strength and number of creeps grow over time. Each side also has two jungles, with some neutral creeps in them. Players control their heroes to kill creeps and enemy heroes to gain gold and experience. Gold can be used to build items strengthening heroes. Experience is for leveling up, heroes can get one spell point each level for one of their four abilities (three basic abilities and one ultimate ability which can only be gained on certain levels). The only way to win is to destroy enemy’s ancient structure right at the very center of their base. Figure 2.1 shows the basic structure ofthe DOTA2map. Figure 2.1DOTA2 minimap Unitsanditems 113 different heroes (Figure 2.2) can be picked by players. Each hero is one of the following three types: Strength, Agility and Intelligence based on their major attributes. Beside these three types, there are more attributes combined on every hero (Figure 2.3) including:Armor, Move speed,Attack speed, Magic resistance, Health/Mana points, Damage, and four abilities with different cool down and damage types, etc. Figure 2.2Hero Profiles