Letting the Player Do What She Wants to Do
Now you can begin devising an appropriate control mechanism to initiate every action the player can take that affects the game (whether within the game world or outside of it, such as saving the game). Refer to the list provided earlier in "What the Player Wants to Do" to get started.
What key actions will the player take to overcome challenges? Refer to the genre chapters in this book for special UI concerns for each genre. What actions unrelated to challenges might she need: move the camera, participate in the story, express herself, or talk to other players online? Create visual and audible feedback for the actions to let the player know if these succeeded or failed.
You'll need to map the input devices to the player's actions, based on the interaction model you have chosen (see "Interaction Models" later in this chapter). Games vary too much to tell you exactly how to achieve a good mapping; study other games in the same genre to see how they use on-screen buttons and menus or the physical buttons, joysticks, and other gadgets on control devices. Use the latter for player actions for which you want to give the player the feeling that she's acting directly in the game without mediation by menus. Whenever possible, borrow tried-and-true techniques to keep it all as familiar as possible.
Work on one gameplay mode at a time, and every time you move to a new game - play mode, be sure to note the actions it has in common with other modes and keep the control mechanisms consistent.
Shell menus allow the player to start, configure, and otherwise manage the operation of the game before and after play. The screens and menus of the shell interface should allow the player to configure the video and audio settings and the game controls (see "Allowing for Customization" later in the chapter), to join in multiplayer games over a network, to save and load games, and to shut down the game software.
The player should not have to spend much time in the shell menus. Provide a way to let players get right into the action with one or two clicks of a button.
A surprising number of games include awkward and ugly shell menus because designers assumed that creating these screens could wait until the last minute. Remember, the shell interface is the first thing your player will see when he starts up the game. You don't want to make a bad impression before the player even gets into the game world.