Most user interfaces require the user to focus on one element at a time, but StarCraft 2 is a game where players often control more than a hundred units simultaneously. The game interface provides an optional mechanism called "control groups" that allows players to select multiple units and assign them to a group in order to quickly recall previous selections of units. From an analysis of over 3,000 replays, we show that the usage of control groups is a key differentiator of individual players as well as players of different skill levels---novice users rarely use control groups while experts nearly always do. But players also behave differently in how they use their control groups, especially in time-pressured situations. While certain control group behaviors are common across all skill levels, expert players appear to be better at remaining composed and sustaining control group use in battle. We also qualitatively analyze discussions on web forums from players about how they use control groups to provide context about how such a simple interface mechanic has produced numerous ways of optimizing unit control.

Players can change the rules of a multi-person game to experience a different gameplay mechanic, add thematic color, or fine-tune its balance. To better understand game variants, we use a grounded approach to analyze 62 variants for Texas Hold'em, a popular card game, and a follow-up case-study of 91 variants of Halo 2, a popular video game. We study their development and examine whether lessons from Texas Hold'em apply to a constrained system such as Halo 2. We discover video gamers' reliance on 'honor rules', rules dependent on the cooperative spirit of its players. We develop a theory of 'necessity' in rule adoption, showing players' sensitivity to the impact of one change on the whole game. In solving game-design problems, adjustments drawn from a set of 'canned' rule changes address common problems with familiar solutions. We find a complex interplay between who can play and what rules are chosen. Our findings have implications for game designers and for variants in non-game contexts.

Video games are primarily designed for the players. However, video game spectating is also a popular activity, boosted by the rise of online video sites and major gaming tournaments. In this paper, we focus on the spectator, who is emerging as an important stakeholder in video games. Our study focuses on Starcraft, a popular real-time strategy game with millions of spectators and high level tournament play. We have collected over a hundred stories of the Starcraft spectator from online sources, aiming for as diverse a group as possible. We make three contributions using this data: i) we find nine personas in the data that tell us who the spectators are and why they spectate; ii) we strive to understand how different stakeholders, like commentators, players, crowds, and game designers, affect the spectator experience; and iii) we infer from the spectators' expressions what makes the game entertaining to watch, forming a theory of distinct types of information asymmetry that create suspense for the spectator. One design implication derived from these findings is that, rather than presenting as much information to the spectator as possible, it is more important for the stakeholders to be able to decide how and when they uncover that information.