Designing the Game
The design of the Battle Office game flows fairly smoothly from the overview of the game that you just went through. You know that there is a background image required to show the office inhabited by the people you're shooting at. You also know that the people themselves can probably be represented by sprites. Granted, not all the people are moving, but keep in mind that sprites can be used in a variety of different ways. For example, you can use a sprite to simply show and hide an image of a person, as well as perform hit testing on the sprite to see if it has been clicked with the mouse. This approach works well for the people hiding behind desks. Similarly, sprites can be used to represent the people running in the back of the office.
To help you get a feel for how the Battle Office game is laid out, take a look at Figure 16.1.
Figure 16.1 The Battle Office game consists of an office with desks that people can hide behind, as well as a hallway that people can run back and forth through.
Notice that the office in the figure includes three desks that are suitable for people to hide behind, along with a hallway. The hallway provides a way for people to run back and forth, which provides you with moving targets to shoot at. Again, the main premise of the game is to shoot at the office workers as they pop up from behind desks and run back and forth down the hallway. In the lower right corner of the game screen, you'll notice that there are boxes to display the number of hits and misses in the game.
As I mentioned earlier, your weapon is up to your imagination; all you use to shoot people is a special bull's-eye sprite designed to follow the mouse pointer. It's probably a little healthier to think in terms of using a "friendly" weapon such as a wad of paper, but this is ultimately up to each individual player. Rather than focus on a weapon, the game instead displays a red bull's-eye that you control with the mouse and use to shoot the people in the office. When you score a hit, a "pow" image is displayed to indicate that you hit the target.
Now that you understand the basics of the game and how it is played, it's time to examine what kinds of sprites need to be used. Following is a list of the sprites that go into the Battle Office game:
Five office worker sprites
The five office worker sprites represent the people in the office who you are shooting at when you play the game. Three of these people sprites are stationary behind desks and simply appear and disappear, while the two others run across the hallway near the back of the office. The target sprite is the bull's-eye that you use to aim with the mouse. Finally, the pow sprite is used to indicate that you've scored a hit, and it is placed directly over the person you've hit. Although you can certainly score multiple hits throughout the game, a single pow sprite is sufficient to represent each hit; the sprite is simply moved to the new hit location when a new hit occurs.
Beyond the sprites, the Battle Office game also requires several bitmaps. Following are the ten bitmap images required of the game:
Background office image
Bull's-eye target image
Five office worker images
Small office worker image
Game over image
Most of these images should be pretty obvious given the game design thus far. However, you're probably curious about the small office worker image, which is used to indicate how many people you've missed. When the game begins, there are no misses, so none of the small worker images are displayed. As the game progresses and some of the people get away, the small worker image is drawn repeatedly to indicate each miss. Five misses results in the game ending; in which case, the game over image is displayed.
Now that you have a feel for the graphical objects involved in the game, let's consider other data that must be maintained by the game. First, it's pretty obvious that you'll need to keep track of how many misses you've had because it determines when the game ends. It's also important to keep track of the number of hits so that you'll have a means of keeping scorethe number of hits is the score in the Battle Office game. A Boolean variable to keep track of whether the game is over is also required.
A couple of other pieces of information that aren't immediately obvious involve the manner in which the office workers are displayed. By the way, when you see the bitmaps, you'll realize that all the workers are men, so I've opted to refer to them as "guys" in the game code. So, I might as well start using the same terminology in this discussion. The game displays the five different guys at random time intervals, which gives the game a more spontaneous feel. In order to establish these intervals, you need to keep track of each guy's time delay. Additionally, the game is much better if it gradually gets harder the longer you play. So, a master delay is used to provide a means of slowly reducing the length of time that the stationary guys appear on screen. In other words, the guys behind the desks slowly begin appearing for shorter periods of time, which makes it harder to shoot them.
To recap the data requirements of the Battle Office game, the game design has led us to the following pieces of information that must be managed by the game:
The number of guys missed
The number of guys hit
A Boolean game over variable
A delay variable for each guy
A master delay variable for controlling the game's difficulty level
With this information in mind, you're now ready to move on and assemble the code for the Battle Office game.