User Interfaces - Fundamentals of Game Design - page 207

■ Pick portable objects up and put them down. If your game includes portable
objects, implement a mechanism for picking them up and putting them down.
This can mean anything from picking up a chess piece and putting it down else-
where on the board to a full-blown inventory system in a role-playing game in
which the player can pick up objects in the environment, add them to the inven-
tory, give them to other characters, buy them, sell them, or discard them again.
Be sure to include checks to prevent items from being put down in inappropriate
places (such as making an illegal move in chess). Some games do not permit players
to put objects down, in order to prevent the players from leaving critical objects
behind.
■ Manipulate fixed objects. Many objects in the environment can be manipu-
lated in place but not picked up, such as light switches and doors. For an avatar-
based game, design a mechanism that works whenever the avatar is close enough to
the object to press it, turn it, or whatever might be necessary. In other interaction
models, let the player interact more directly with fixed objects by clicking them.
You can simplif y this process by giving fi xed objects a limited number of states
through which they may be rotated: a light switch is on or off; curtains are fully
open, halfway open, or closed.
■ Construct and demolish objects. Any game that allows the player to build
things needs suitable control mechanisms for choosing something to build or
materials to build with, selecting a place to build, and demolishing or disassem-
bling already-built objects. It also requires feedback mechanisms to indicate where
the player may and may not build, what materials he has available, and if appropri-
ate, what it will cost. You should also include controls for allowing him to see the
structure in progress from a variety of angles. For further discussion of construc-
tion mechanisms, see Chapter 18, “Construction and Management Simulations.”
■ Conduct negotiations and financial transactions, and set numeric values.
In complex simulations, players sometimes need to deal with numbers directly,
especially when managing quantities of intangible resources such as money.
Conventional user interfaces for desktop applications employ many ways of obtain-
ing a number from the user—typed characters, scrolling list boxes, sliders, and so
on. Unfortunately, most of these prosaic mechanisms harm the player's fantasy
unless he is playing a game set in the modern world. If you need to let the player
manipulate raw numbers, try to find a way—perhaps with appropriate artwork and
consistent typefaces—to make it fit into your game's cultural style.
■ Give orders to units or characters. Players need to give orders to units or char-
acters in many types of games. Typically this requires a two- or three-step process:
designating the unit to receive the order, giving the order, and optionally giving
the object of the order, or target . Orders take the form of verbs, such as attack , hug ,
open , or unload , and targets take the form of direct objects for the verbs, such as thug ,
dog , crate , or truck , indicating what the unit should attack, hug, open, or unload.