- How Does the Game Play?
- Designing the Game
- Building the Game
- Testing the Game
- Summary
- Q&A
- Workshop
This chapter is from the book
This chapter is from the book
This chapter is from the book
Building the Game
The construction of the Battle Office game follows the same pattern you've grown accustomed to in other programs' examples and games. The next few sections guide you through the development of the game's code and resources.
Writing the Program Code
The code for the Battle Office game begins in the BattleOffice.h header file, which is responsible for declaring the global variables used throughout the game. Listing 16.1 contains the code for this file.
Listing 16.1 The BattleOffice.h Header File Declares Global Variables That Are Used to Manage the Game
1: #pragma once 2: 3: //----------------------------------------------------------------- 4: // Include Files 5: //----------------------------------------------------------------- 6: #include <windows.h> 7: #include "Resource.h" 8: #include "GameEngine.h" 9: #include "Bitmap.h" 10: #include "Sprite.h" 11: 12: //----------------------------------------------------------------- 13: // Global Variables 14: //----------------------------------------------------------------- 15: HINSTANCE _hInstance; 16: GameEngine* _pGame; 17: HDC _hOffscreenDC; 18: HBITMAP _hOffscreenBitmap; 19: Bitmap* _pOfficeBitmap; 20: Bitmap* _pTargetBitmap; 21: Bitmap* _pPowBitmap; 22: Bitmap* _pGuyBitmaps[5]; 23: Bitmap* _pSmallGuyBitmap; 24: Bitmap* _pGameOverBitmap; 25: Sprite* _pTargetSprite; 26: Sprite* _pPowSprite; 27: Sprite* _pGuySprites[5]; 28: int _iGuyDelay[5]; 29: int _iGuyMasterDelay; 30: int _iHits; 31: int _iMisses; 32: BOOL _bGameOver;
As the listing reveals, the global variables for the Battle Office game largely consist of the different bitmaps that are used throughout the game. The offscreen device context and bitmap are declared first (lines 17 and 18), as well as the different bitmaps that make up the game's graphics (lines 19–24). The sprite variables for the game are declared after the bitmaps, and include the target sprite, the pow sprite, and the five guy sprites (lines 25–27). The delays for each of the five guys are then declared (line 28), along with the master delay that controls the game's difficulty level (line 29). Finally, the number of hits and misses are declared (lines 30 and 31), as well as the familiar game over Boolean variable (line 32).
The initialization of the game variables primarily takes place in the GameStart() function, which is shown in Listing 16.2.
Listing 16.2 The GameStart() Function Initializes the Bitmaps, Sprites, and Game State Variables
1: void GameStart(HWND hWindow)
2: {
3: // Seed the random number generator
4: srand(GetTickCount());
5:
6: // Create the offscreen device context and bitmap
7: _hOffscreenDC = CreateCompatibleDC(GetDC(hWindow));
8: _hOffscreenBitmap = CreateCompatibleBitmap(GetDC(hWindow),
9: _pGame->GetWidth(), _pGame->GetHeight());
10: SelectObject(_hOffscreenDC, _hOffscreenBitmap);
11:
12: // Create and load the bitmaps
13: HDC hDC = GetDC(hWindow);
14: _pOfficeBitmap = new Bitmap(hDC, IDB_OFFICE, _hInstance);
15: _pTargetBitmap = new Bitmap(hDC, IDB_TARGET, _hInstance);
16: _pPowBitmap = new Bitmap(hDC, IDB_POW, _hInstance);
17: _pGuyBitmaps[0] = new Bitmap(hDC, IDB_GUY1, _hInstance);
18: _pGuyBitmaps[1] = new Bitmap(hDC, IDB_GUY2, _hInstance);
19: _pGuyBitmaps[2] = new Bitmap(hDC, IDB_GUY3, _hInstance);
20: _pGuyBitmaps[3] = new Bitmap(hDC, IDB_GUY4, _hInstance);
21: _pGuyBitmaps[4] = new Bitmap(hDC, IDB_GUY5, _hInstance);
22: _pSmallGuyBitmap = new Bitmap(hDC, IDB_SMALLGUY, _hInstance);
23: _pGameOverBitmap = new Bitmap(hDC, IDB_GAMEOVER, _hInstance);
24:
25: // Create the target, pow, and guy sprites
26: RECT rcBounds = { 0, 0, 500, 400 };
27: _pTargetSprite = new Sprite(_pTargetBitmap, rcBounds, BA_STOP);
28: _pTargetSprite->SetZOrder(4);
29: _pGame->AddSprite(_pTargetSprite);
30: _pPowSprite = new Sprite(_pPowBitmap, rcBounds, BA_STOP);
31: _pPowSprite->SetZOrder(3);
32: _pPowSprite->SetHidden(TRUE);
33: _pGame->AddSprite(_pPowSprite);
34: _pGuySprites[0] = new Sprite(_pGuyBitmaps[0], rcBounds);
35: _pGuySprites[0]->SetPosition(92, 175);
36: _pGuySprites[0]->SetZOrder(2);
37: _pGuySprites[0]->SetHidden(TRUE);
38: _pGame->AddSprite(_pGuySprites[0]);
39: _pGuySprites[1] = new Sprite(_pGuyBitmaps[1], rcBounds);
40: _pGuySprites[1]->SetPosition(301, 184);
41: _pGuySprites[1]->SetZOrder(2);
42: _pGuySprites[1]->SetHidden(TRUE);
43: _pGame->AddSprite(_pGuySprites[1]);
44: _pGuySprites[2] = new Sprite(_pGuyBitmaps[2], rcBounds);
45: _pGuySprites[2]->SetPosition(394, 61);
46: _pGuySprites[2]->SetZOrder(2);
47: _pGuySprites[2]->SetHidden(TRUE);
48: _pGame->AddSprite(_pGuySprites[2]);
49: rcBounds.left = 340;
50: _pGuySprites[3] = new Sprite(_pGuyBitmaps[3], rcBounds, BA_WRAP);
51: _pGuySprites[3]->SetPosition(500, 10);
52: _pGuySprites[3]->SetVelocity(-3, 0);
53: _pGuySprites[3]->SetZOrder(1);
54: _pGuySprites[3]->SetHidden(TRUE);
55: _pGame->AddSprite(_pGuySprites[3]);
56: rcBounds.left = 385;
57: _pGuySprites[4] = new Sprite(_pGuyBitmaps[4], rcBounds, BA_WRAP);
58: _pGuySprites[4]->SetPosition(260, 60);
59: _pGuySprites[4]->SetVelocity(5, 0);
60: _pGuySprites[4]->SetZOrder(1);
61: _pGuySprites[4]->SetHidden(TRUE);
62: _pGame->AddSprite(_pGuySprites[4]);
63:
64: // Initialize the remaining global variables
65: _iGuyMasterDelay = 50;
66: _iHits = 0;
67: _iMisses = 0;
68: _bGameOver = FALSE;
69:
70: // Play the background music
71: _pGame->PlayMIDISong(TEXT("Music.mid"));
72: }
I know; that's a heck of a lot of code for a function whose only job is to get the game started. However, you have to consider what all it takes to start a game like this. The bitmaps must be loaded (lines 14–23) and the sprites created (lines 26–62)—not to mention initializing the other global variables in the game (lines 65–68) and starting the background music (line 71). Of course, a few specific parts of this function are worth closer attention.
First, notice that the target sprite is set so that it stops when it reaches the boundary of the game screen (line 27). This ensures that the bull's-eye target is always visible on the screen no matter where you drag the mouse. Similarly, the pow sprite is also given the stop bounds action, as well as being hidden when the game first starts (line 32). This sprite is only displayed when a successful hit is made, which is why it begins the game hidden. At this point it's worth pointing out that the Z-order of the target sprite is set higher than the pow sprite (line 28), whereas the pow sprite's Z-order is set higher than the guy sprites (line 31). This results in the target sprite always appearing on top of the other sprites, while the pow sprite appears on top of the guys.
The first three guy sprites are created at fixed positions on the screen and are also hidden (lines 34–48). The fixed positions are already calculated to display each guy so that he appears to be standing behind the desks in the background office image. The remaining two guy sprites are designed to move across the hallway section of the office background. For this reason, the sprites are given velocities that cause them to move horizontally across the screen (lines 52 and 59). These sprites are also hidden, which allows the game to start with no guys in the office.
The other global variables in the Battle Office game are initialized with values suitable for the game's start. For example, the master delay for the guys is set to 50 (line 65), which is a value that you'll get a better understanding of a little later in the hour. The hits and misses are then zeroed out (lines 66 and 67), and the game over variable is set to FALSE (line 68). Finally, the PlayMIDISong() method of the game engine is used to start playing the background music for the game (line 71).
Although it is longer than what you've seen in most of the examples throughout the book thus far, the GameEnd() function is still much smaller than the GameStart() function that you just saw. Listing 16.3 contains the code for the GameEnd() function.
Listing 16.3 The GameEnd() Function Cleans Up After the Game
1: void GameEnd()
2: {
3: // Close the MIDI player for the background music
4: _pGame->CloseMIDIPlayer();
5:
6: // Cleanup the offscreen device context and bitmap
7: DeleteObject(_hOffscreenBitmap);
8: DeleteDC(_hOffscreenDC);
9:
10: // Cleanup the bitmaps
11: delete _pOfficeBitmap;
12: delete _pTargetBitmap;
13: delete _pPowBitmap;
14: for (int i = 0; i < 5; i++)
15: delete _pGuyBitmaps[i];
16: delete _pSmallGuyBitmap;
17: delete _pGameOverBitmap;
18:
19: // Cleanup the sprites
20: _pGame->CleanupSprites();
21:
22: // Cleanup the game engine
23: delete _pGame;
24: }
As you can see, this function is responsible for performing a variety of different cleanup tasks for the Battle Office game. The first step is to close the MIDI player (line 4). The bitmaps and sprites are then wiped away (lines 7–20), and the game engine is deleted (line 23).
Because the Battle Office game plays MIDI music, you know that it's important to pause and resume the music appropriately when the game is deactivated and reactivated. This takes place in the familiar GameActivate() and GameDeactivate() functions, which you've already seen performing this task in other examples.
The game screen in the Battle Office game is painted entirely by the GamePaint() function, which is shown in Listing 16.4.
Listing 16.4 The GamePaint() Function Draws the Office Background Bitmap, the Sprites, and the Number of Hits and Misses
1: void GamePaint(HDC hDC)
2: {
3: // Draw the background office
4: _pOfficeBitmap->Draw(hDC, 0, 0);
5:
6: // Draw the sprites
7: _pGame->DrawSprites(hDC);
8:
9: // Draw the number of guys who were hit
10: TCHAR szText[64];
11: RECT rect = { 237, 360, 301, 390 };
12: wsprintf(szText, "%d", _iHits);
13: DrawText(hDC, szText, -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
14:
15: // Draw the number of guys who were missed (got away)
16: for (int i = 0; i < _iMisses; i++)
17: _pSmallGuyBitmap->Draw(hDC, 389 + (_pSmallGuyBitmap->GetWidth() * i),
18: 359, TRUE);
19:
20: // Draw the game over message, if necessary
21: if (_bGameOver)
22: _pGameOverBitmap->Draw(hDC, 120, 110, TRUE);
23: }
This GamePaint() function is responsible for drawing all the game graphics for the game. The function begins by drawing the background office image (line 4), and then it draws the game sprites (line 7). The remainder of the function primarily draws the number of hits and misses in the lower right corner of the game screen. The hits are drawn as a number using the Win32 DrawText() function (lines 10–13). The misses, on the other hand, are drawn using small guy bitmaps (lines 16–18). A small guy is drawn for each guy who was missed, which helps you to know how many guys can escape before the game ends.
The GameCycle() function controls most of the game play in the Battle Office game, and also works closely with GamePaint() to update the game's sprites and reflect the changes onscreen. Listing 16.5 shows the code for the GameCycle() function.
Listing 16.5 The GameCycle() Function Randomly Controls the Guys in the Office and Determines if the Game Has Ended
1: void GameCycle()
2: {
3: if (!_bGameOver)
4: {
5: // Randomly show and hide the guys
6: for (int i = 0; i < 5; i++)
7: if (_pGuySprites[i]->IsHidden())
8: {
9: if (rand() % 60 == 0)
10: {
11: // Show the guy
12: _pGuySprites[i]->SetHidden(FALSE);
13:
14: // Start the countdown delay
15: if (i == 3)
16: {
17: // Start the guy running left
18: _iGuyDelay[i] = 80;
19: _pGuySprites[i]->SetPosition(500, 10);
20: }
21: else if (i == 4)
22: {
23: // Start the guy running right
24: _iGuyDelay[i] = 45;
25: _pGuySprites[i]->SetPosition(260, 60);
26: }
27: else
28: // Start the stationary guys
29: _iGuyDelay[i] = 20 + (rand() % _iGuyMasterDelay);
30: }
31: }
32: else
33: {
34: if (--_iGuyDelay[i] == 0)
35: {
36: // Play a sound for the guy getting away
37: PlaySound((LPCSTR)IDW_TAUNT, _hInstance, SND_ASYNC |
38: SND_RESOURCE);
39:
40: // Hide the guy
41: _pGuySprites[i]->SetHidden(TRUE);
42:
43: // Increment the misses
44: if (++_iMisses == 5)
45: {
46: // Play a sound for the game ending
47: PlaySound((LPCSTR)IDW_BOO, _hInstance, SND_ASYNC |
48: SND_RESOURCE);
49:
50: // End the game
51: for (int i = 0; i < 5; i++)
52: _pGuySprites[i]->SetHidden(TRUE);
53: _bGameOver = TRUE;
54:
55: // Pause the background music
56: _pGame->PauseMIDISong();
57: }
58: }
59: }
60:
61: // Update the sprites
62: _pGame->UpdateSprites();
63:
64: // Obtain a device context for repainting the game
65: HWND hWindow = _pGame->GetWindow();
66: HDC hDC = GetDC(hWindow);
67:
68: // Paint the game to the offscreen device context
69: GamePaint(_hOffscreenDC);
70:
71: // Blit the offscreen bitmap to the game screen
72: BitBlt(hDC, 0, 0, _pGame->GetWidth(), _pGame->GetHeight(),
73: _hOffscreenDC, 0, 0, SRCCOPY);
74:
75: // Cleanup
76: ReleaseDC(hWindow, hDC);
77: }
78: }
The GameCycle() function is one of the heftiest functions you've seen thus far in the book, and there's a good reason for it. This function is carrying out a great deal of the Battle Office game logic by determining when and how the office guys appear. The function first loops through the five guy sprites (line 6), checking to make sure that each one is hidden before attempting to show it (line 7). If the guy is hidden, he is first made visible (line 12). And then some interesting things take place, depending on which guy is being shown. If one of the moving guys is being shown, which is indicated by an array index value of 3 or 4, a countdown delay is started and the sprite position is set (lines 15–26). The position makes sure that the guy starts moving from the edge of the game screen, while the delay gives them just enough time to run across the hallway before being hidden again. If the guy sprite is not one of the moving guys, a delay is set that is based on the master delay, which gets shorter as the game progresses (line 29). The idea is that the stationary guys will be displayed for shorter and shorter periods of time as the game continues.
If the first sprite check inside the loop showed that the guy sprite was already being displayed, the delay is decreased and checked to see if the guy has been shown long enough to hide him again (line 34). In other words, this is the part of the game logic that counts down the delay and results in each guy only being on the screen for a limited amount of time before hiding again. If the delay gets to 0 before the guy is shot, he gets away. If a guy gets away, the first step is to play a sound effect to let the player know (lines 37 and 38). The guy sprite is then hidden (line 41), and the number of misses is increased by one (line 44).
Because the number of misses is being increased, this is a good spot to check and see if the game is over (line 44 also). If there have been five misses, the game is over. A sound effect is played to let the player know that the game is over (lines 47 and 48), and the guy sprites are all hidden (lines 51 and 52). Ending the game also involves setting the _bGameOver variable (line 53), as well as stopping the MIDI music (line 56). In this case, the music is only paused—there is no reason to close the MIDI device just yet because the player might decide to start another game.
The remaining code in the GameCycle() function should be familiar to you because it is fairly generic game code. More specifically, it updates the sprites (line 62), and then draws the game graphics using double-buffer animation (line 65–76).
You survived the GameCycle() function, which was about as messy as the code in this book gets. Listing 16.6 contains another important function in the Battle Office game, MouseButtonDown().
Listing 16.6 The MouseButtonDown() Function Checks to See if a Guy Was Clicked with the Mouse
1: void MouseButtonDown(int x, int y, BOOL bLeft)
2: {
3: // Only check the left mouse button
4: if (!_bGameOver && bLeft)
5: {
6: // Temporarily hide the target and pow sprites
7: _pTargetSprite->SetHidden(TRUE);
8: _pPowSprite->SetHidden(TRUE);
9:
10: // See if a guy sprite was clicked
11: Sprite* pSprite;
12: if ((pSprite = _pGame->IsPointInSprite(x, y)) != NULL)
13: {
14: // Play a sound for hitting the guy
15: PlaySound((LPCSTR)IDW_WHACK, _hInstance, SND_ASYNC | SND_RESOURCE);
16:
17: // Position and show the pow sprite
18: _pPowSprite->SetPosition(x - (_pPowSprite->GetWidth() / 2),
19: y - (_pPowSprite->GetHeight() / 2));
20: _pPowSprite->SetHidden(FALSE);
21:
22: // Hide the guy that was clicked
23: pSprite->SetHidden(TRUE);
24:
25: // Increment the hits and make the game harder, if necessary
26: if ((++_iHits % 5) == 0)
27: if (--_iGuyMasterDelay == 0)
28: _iGuyMasterDelay = 1;
29: }
30:
31: // Show the target sprite again
32: _pTargetSprite->SetHidden(FALSE);
33: }
34: else if (_bGameOver && !bLeft)
35: {
36: // Start a new game
37: _bGameOver = FALSE;
38: _iHits = 0;
39: _iMisses = 0;
40:
41: // Restart the background music
42: _pGame->PlayMIDISong();
43: }
44: }
The MouseButtonDown() function responds to mouse clicks in the game and serves as a means of determining if the player scored a hit on one of the office guys. The function first checks to make sure that the game isn't over and that the player clicked the left mouse button (line 4). If so, the target and pow sprites are temporarily hidden so that they don't interfere with performing a hit test on the mouse position (lines 7 and 8). This is necessary because the next task in the function is to see if the mouse position lies within any of the guy sprites. Because the target and pow sprites have a higher Z-order than the guys, they would always supercede the guys. In other words, the hit test would always return either the target or pow sprites and would never detect any of the guys.
The MouseButtonDown()function checks to see if one of the guy sprites was clicked by calling the IsPointInSprite() method on the game engine and passing in the mouse coordinates (line 12). If one of the guys was hit, a sound effect is played (line 15) and the pow sprite is positioned and displayed to indicate the successful hit (lines 18–20). The guy sprite who was hit is then hidden (line 23), which makes sense considering that he's been shot. The number of hits is then increased and checked to see if the difficulty level of the game needs to increase (line 26). The difficulty level is raised by decreasing the master delay for the guys (lines 27 and 28), which determines how long the stationary guys appear on the screen. Regardless of whether a hit was detected on a guy sprite, the target sprite is made visible after performing the test (line 32).
The last block of code in the function allows you to right-click to start a new game (lines 34–43). A new game is started by resetting the game state variables (lines 37–39) and restarting the background MIDI music (line 42).
Another mouse-related function used in the Battle Office game is MouseMove(), which is used to move the target sprite so that it tracks the mouse pointer. This is necessary so that you are always in control of the target sprite with the mouse. Listing 16.7 shows the code for the MouseMove() function.
Listing 16.7 The MouseMove() Function Tracks the Mouse Cursor with the Target Sprite
1: void MouseMove(int x, int y)
2: {
3: // Track the mouse with the target sprite
4: _pTargetSprite->SetPosition(x - (_pTargetSprite->GetWidth() / 2),
5: y - (_pTargetSprite->GetHeight() / 2));
6: }
The target sprite is made to follow the mouse pointer by simply calling the SetPosition() method on the sprite and passing in the mouse coordinates (lines 4 and 5). The position of the target sprite is actually calculated so that the mouse pointer points at the center of the sprite.
The last function of interest in the Battle Office game is the SpriteCollision() function, which is called in response to sprites colliding. Listing 16.8 shows how uneventful the SpriteCollision() function is in this game.
Listing 16.8 The SpriteCollision() Function Does Nothing Because There is No Need to Respond to Sprite Collisions
1: BOOL SpriteCollision(Sprite* pSpriteHitter, Sprite* pSpriteHittee)
2: {
3: return FALSE;
4: }
When you think about how the Battle Office game works, there is no reason to respond to any sprite collisions. Therefore, the SpriteCollision() function simply returns FALSE to indicate that nothing special is to take place in response to a collision (line 3) .