Contents lists available at ScienceDirect Entertainment Computing journal homepage: www.elsevier.com/locate/entcom MOBA games: A literature review Marçal Mora-Cantallops ⁎ , Miguel-Ángel Sicilia University of Alcalá, Alcalá de Henares, Madrid, Spain ARTICLE INFO Keywords: MOBA Multiplayer online battle arena Literature review League of Legends LOL DotA ABSTRACT This article aims to perform a literature review of the available research that focuses strictly on MOBA (mul- tiplayer online battle arena) games. First, a review identifying the relevant papers published since 2011 is conducted, exploring them systematically to extract similarities, gaps and main findings. Results show how League of Legends is the most explored game, with player experience and toxic behaviour as popular topics for research. Second, as MOBA games remain underexplored by researchers despite their vast, enthusiast commu- nity, as well as projection and influence on contemporary game designers, a proposal on future lines for research is provided. 1. Introduction Some 205 million people watched or played eSports in 2014 [3]. Among them, MOBA games are in the lead, both in players and watchers. The League of Legends Championship sold out Staples Center in 2013, then sold out the 40,000-seat World Cup Stadium in Seoul a year later while drawing an online audience of 27 million. However, even though many players are drawn every day to MOBA games, re- search on the subject is still at an early stage. This paper aims to reflect the current research landscape focused strictly on MOBA games, in order to provide a summary of the topics covered and to open venues for new lines of investigation. Existing studies acknowledge the early stage of current research on MOBA games. “Despite its vast, enthusiast community and influence on contemporary game designers, the MOBA remains under-explored by academics” [9]. But few games exhibit a greater need for socially-aware services than this relatively new genre [17] which brings new ways of collaboration and competition on the table, gender and cultural chal- lenges and even new social networks which need to deal with the in- herent toxic behaviour that arises in these contexts. In essence, MOBA games are a subgenre of real-time strategy games in which two teams, typically consisting of five players each, compete against each other with each player controlling a single character. Contrary to real-time strategy games, there is no unit or building con- struction in a MOBA game, so “much of the strategy revolves around individual character development and cooperative team play in combat” [33]. Two of the three most played PC games are MOBA games: League of Legends and DOTA 2 [5]. And yet, it all started from a small and niche fan-made custom map for Blizzard’s real-time strategy (RTS) game StarCraft, Aeon of Strife (AoS), back in 1998, by a modder (an in- dividual who deliberately modifies games to his advantage or for fun) called Aeon64. While AoS set the basics, it wasn’t until Defense of the Ancients (DOTA) when the MOBA genre was born as we know it today. In 2009, Riot Games released League of Legends (LoL) with a com- pletely different pricing approach: it was free to play. Anyone could download it and play with a rotating selection of heroes and some limitations – extra content could be purchased in-game, though. Besides LoL, the second most popular MOBA game as of today (with more than 11 million unique players per month according to their website) is DOTA 2, which was released in 2013 through Valve’s STEAM digital store. Both games are similar in concept but they differ in execution; overall, League of Legends simplified DOTA while DOTA 2 is often considered more demanding and strategically complex than LoL. Moreover, both feature a massive number of players, although LoL has a significantly larger player base. However, they are not alone: a myriad of other titles such as Smite [30], Heroes of Newerth and Heroes of the Storm, the recent entry from Blizzard itself, are also played by millions of players every month. Mobile MOBAs do exist too, with titles such as Vainglory. MOBAs provide an unprecedented research opportunity due to the combination of two factors: the huge number of players (and eSports viewers) they attract and how easy it is to access part of the generated and recorded in-game data. APIs (functions allowing the creation of applications which access such applications’ data and retrieve it) are available and even officially supported. There are, however, some problematic features too: MOBA games are often patched, so the game changes regularly. Professional teams are unstable, frequently https://doi.org/10.1016/j.entcom.2018.02.005 Received 19 February 2017; Received in revised form 14 February 2018; Accepted 19 February 2018 ⁎ Corresponding author. E-mail address: marcal.mora@edu.uah.es (M. Mora-Cantallops). Entertainment Computing 26 (2018) 128–138 Available online 21 February 2018 1875-9521/ © 2018 Elsevier B.V. All rights reserved. T