FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Navigation Mechanisms
Navigation mechanisms allow the player to tell a character, vehicle, or other mobile unit how to move. This section uses the term avatar to refer to anything that the player controls directly, including vehicles. It also uses the word steering to describe the act of directly controlling both vehicles and characters, even though the idea of steering a walking character may sound a little odd. UI designers usually find creating vehicle navigation systems easier than creating ones for characters because input devices more closely resemble a vehicle's controls than they do an avatar's body.
A navigation mechanism establishes a relationship between the way the player moves the controls and the way the avatar responds on the screen. The player learns this relationship and uses it until it becomes automatic. When a player gives movement commands, the avatar must respond in a consistent and predictable way. Anything that disrupts the player's understanding of the control relationship, such as a sudden change of camera angles, may cause the player to make a steering error.
This section assumes that players steer using a joystick except where otherwise indicated; for most purposes, you may consider a joystick interchangeable with a D-pad but offering finer control. Joystick directions are referred to as up (forward or away from the player), down (towards the player), left, and right. Steering wheels for cars or control yokes for aircraft aren't covered here because they should be self-explanatory.
If the player designates a point in the landscape and the character or vehicle moves to that target without further player control, the game uses point-and-click navigation.
