Input is the player’s organ of expression in the game world, the only way a player can speak to the game. This is an overlooked aspect of game feel: the tactile feel of the input device. Games played with a good-feeling controller feel better. The Xbox 360 controller feels good to hold; it’s solid, has the proper weight, and is pleasingly smooth to the touch. By contrast, the PS3 controller has been lamented as being light and “cheap [feeling], like one of those third party knockoffs.”
This difference in tactile feel of the input device has implications for the feel of a given game. When I prototype something -- platformer, racing game, whatever -- it will feel noticeably better if I hook up the inputs to my wired Xbox 360 controller than to simple keyboard inputs. You can’t always control the input device your player is going to use to interface with your game so you should be aware of, and compensate for, how different input devices feel. One way to lean into a given input device is through natural mappings.
A natural mapping is a clear, intuitive relationship between possible actions and their effect on the system. Consider three possible configurations of burners and dials on a stove:
Imagine trying to use each of them. Which one requires no thought to operate? Clearly, figure C is a natural mapping: the layout of the dials correspond clearly and obviously to the burners they activate. There is a clean, physical metaphor connecting the input device and the way it can alter the system. A good example from a modern game is Geometry Wars for Xbox 360.
Look at Geometry Wars relative to the Xbox360 controller. Notice the way that the joystick is formed, and how that transposes almost exactly to the motion in Geometry Wars. It’s almost one for one: the joystick sits in a circular plastic housing that constrains its motion in a circular way. Pushing the control stick against the edge of the plastic rim that contains it and rolling it back and forth creates little circles, which is almost exactly the analogous motion produced on screen by Geometry Wars in response to input. This is what Donald Norman’s would refer to as a “natural mapping.” There’s no explanation or instruction needed because the position and motion of the input device correlates exactly to the position and motion of the thing being controlled in the game. The controls of Mario 64 also have this property; the rotation of the thumbstick correlates very closely to the rotation of Mario as he turns, twists, and abruptly changes direction.
Another way input device affects game feel is through the inherent sensitivity of the input device. Consider the difference between a button and a computer mouse. A typical button has two states, on or off. It can be in one of two positions. As an input device, it has very little sensitivity. By contrast, a typical computer mouse has complete freedom of movement along two axes. It is unbounded; you can move it as far as the surface underneath allows, giving it a huge number of possible states. A mouse is an extremely sensitive input device.
So an input device can have an inherent amount of sensitivity, falling somewhere between a mouse (near-complete freedom in two axes) and a button (only two states, on or off.) This is what I call input sensitivity; a rough measure of the amount of expressiveness inherent in a particular input device.
The implication for game feel prototyping is to consider the sensitivity of your input device relative to how fluid and expressive you want your game to be. In most cases, this is a decision about complexity -- as a general rule, additional sensitivity means greater complexity. This is not a value judgment per se; greater sensitivity has both benefits and drawbacks depending on the goals of the design and how the mechanic fits into that design. What’s important to realize is the implications your choice of input device has for the sensitivity of the game. Of course, the input device is only half the picture. The other place to define sensitivity is in reaction: how does the game process -- and respond to -- the input it receives from the input device.
Consider two following games, Zuma and Strange Attractors:
In Zuma, there is a reduction in the inherent sensitivity of the mouse as an input device. Instead of freedom of movement in two axes, the object being controlled is stationary. The frog character rotates in place, always looking at the cursor, clamping the mouse’s sensitivity down to something more manageable.
By contrast, Strange Attractors is a game which uses only one button as input. The position of your ship in space is always fluid, always changing very subtly, and you can manipulate it only by activating or deactivating the various gravity wells around the level. Both Strange Attractors and Zuma have fairly sensitive, nuanced reactions to input. This is reaction sensitivity: sensitivity created by mapping user input to game reaction to produce more (or less) sensitivity in the overall system. It is in this space -- between player and game -- where the core of game feel is defined.