A game is a system of constraints. Whether it’s Solitaire or Call of Duty, the player is restricted in what he can do. When we play any game, what we’re really doing is trying to beat the constraints. Sometimes beating the constraints can mean optimizing statistical probabilities in your favor. It could be reading your opponent and trying to figure out what sets of constraints you can impose on her, and conversely, how to deal with the constraints that she can impose on you. Whatever it is, constraints are central to any game.
Now let’s compare two similar games, Chess and Checkers. With tournaments across the globe and the prestigious title of Grandmaster, Chess is taken seriously. Checkers, on the other hand, is something you would play with your ten year old brother. The rules of Checkers is simple; your pieces can move forward in a diagonal pattern, and you remove opposing pieces from play by “leaping” over their pieces. If you get a piece to the opposite end of the board, it gets promoted and can now move backwards. Chess has a myriad of rules which are far too many to discuss.
An important distinction to note is that it’s not the number of rules that necessarily creates constraint. For instance, Go is very simple but is on parity with Chess in complexity. What ultimately matters is the ability to maneuver around constraints. In Starcraft, one of the major constraint is resources. Initially, the player has little choice in what he can do, but as the game progresses, he can choose to expand to acquire more resources, build less resource intensive units, or even cripple his opponent’s economy to give himself a relative advantage.
The key goal of a successful game is have enough maneuverability around constraints so that it grants the player enough freedom to experiment. When there’s too few constraints, the game becomes too easy, but with too many constraints, the game becomes static with little room for novel strategies.