FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Player Actions
Action games routinely allow moving or maneuvering an avatar; aiming and shooting; selecting, collecting, manipulating, or modifying objects; and various kinds of fighting moves—punching, kicking, defending, and so on. Platformers naturally include a number of moves for climbing and jumping. 3D shooters frequently offer a number of specialized activities associated with infantry combat, including crouching or lying prone to avoid fire and improve one's aim, dropping and rolling to get out of danger, and peeking out from behind cover.
Two specialty actions—smart bombs and hyperspace escape—are characteristic of action games and are seldom found anywhere else. They're normally found in high-speed 2D games. A smart bomb sounds like an object, but it's usually implemented as an action available to the player. Pressing the smart bomb button clears the area immediately surrounding the avatar, typically leaving it entirely free of enemies, although the range cleared varies from game to game. Because the smart bomb is so powerful, you should make it costly, generally by making it available only once or by making its effect diminish every time it is used. Because the player doesn't know what lies ahead, he is always faced with the decision of whether to use it in a given situation or to try to make do without it in case he gets into even worse trouble later on.
Hyperspace escape is a button or other player-selectable option that instantly moves the player's avatar to another location in the game world, normally at random. It's a means of getting out of trouble. However, unlike the smart bomb, a hyperspace escape is just as likely to land the avatar in an equally difficult situation as it is to transport it to safety. Asteroids provides an example of the early use of hyperspace escape. Designers usually allow players to use the hyperspace button more frequently than the smart bomb because the usefulness of the maneuver is balanced by the chance that the avatar could end up in an even worse situation. Ironically, the more likely the Asteroids player is to need it (usually because of the amount of debris on the playfield), the more risk there is to the player.
