South Park Gauntlet

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One of the more popular games for the Commodore 64 and even Nintendo was Gauntlet. In this game, the player moved his character around on a map, killing enemies and finishing level after level. We will be creating a similar game using those lovable scamps from the Comedy Central TV show South Park.

In this game, you are Eric Cartman. The aliens have come down and are trying to give you an anal probe. Don't let them catch you and kill them by shooting Cheezy poofs at them.

Moving Around
Players will move around using the keyboard. The arrow keys will move the character on the screen. There will also be keys to allow firing in 4 directions. Movement will be a constant amount in any direction, so sprites will move with a constant speed. Bullets will move faster than the character, who will move faster than the enemies.
Graphics
The players, bullets, enemies, and walls on the map will be represented as sprites. Moving the sprites simply requires drawing the background and drawing the sprite at its new location. The background will remain static until scrolling is necessary, at which point it will be regenerated using map tiles and loaded into the background buffer.
Sound
We will include sound effects for firing and dying. The sound will be implemented using a circular buffer and adding sounds into it as they need to be played.
Enemy Movements
Enemy movements will be calculated as follows:
If a player is within a certain distance to the enemy, move towards it. Otherwise, stay put. While moving towards the player, if an obstacle is encountered, the enemy's movement has a 50% chance of continuing in the same direction, and a 50% chance of being in any of the three other directions. This way, the enemy doesn't get stuck behind an obstacle (wall, other enemy), but doesn't hunt down the player.

Character
• x_pos - The x position of the character in the world array
• y_pos - The y position of the character in the world array
• delta_x - The change in x_pos
• delta_y - The change in y_pos
• hit_pts - Health of this character left
• weapon - The current weapon in use
• enemy_flag - Is this character an enemy to the current player?
• facing - Direction last facing
• anim_no - The animation number in the sequence of movements
• score
• id - Identifier for this character
Bullet
• xpos - The x position of the bullet in the world array
• ypos - The y position of the bullet in the world array
• direction - Direction it is travelling
• time - Time this bullet has been 'alive'
• owner - Who shot this bullet?
Map - An array of characters used to determine what walls lie where in the world.
Friends - Array of character structs used to hold data on player
Enemies - Array of character structs used to hold data on aliens
Bullets - Array of bullet structs used to hold data on bullets
SoundBuf - A buffer in memory used for storing sounds to be played
MidiBuf - A buffer in memory used for storing midi sound to be played
Spriteoffsets - Lookup table of offsets of each sprite in the sprites.pcx file.

MAP_X - X location of the upper left hand portion of the map to draw on the screen.
MAP_Y - Y location of the upper left hand portion of the map to draw on the screen.
SpriteOffsets - Array that holds the offset of sprites. SpriteOffsets[Map.dat] gives the offset of the tile at that map.dat position
Update_Positions - A variable used to control timing in the game. Gets incremented 18 times a second
Keyboard variables - Variables similar to the ones in MP4 used to determine direction of movement.
CARTMAN_DEAD - Flag to see if the character has died.
AllDead - Flag to see if the enemies are all dead.
QUIT_GAME - Flag to see if we want to stop playing.
EXIT_GAME - Flag to see if we want to exit to DOS.

PlayMidi - (Paul) Setup to play Midi sound. Load file then place into MidiBuf.
• Requires the midifile.
• Requires midiname
• Calls RegisterMidi, MidiPlay

• Inputs	Outputs
  midifile	MidiBuf
  midiname	MidiSeg

RegisterMidi - (Paul) Register an XMIDI file by address for playback.
• Requires the segment and offset of the MidiBuf.

• Inputs	Outputs
  Offset of MidiBuf	AX - whether or not the data was registered
  Segment of MidiBuf	-

MidiPlay - (Paul) Plays a sequence from the currently registered xmidi file.

• Inputs	Outputs
  none	none

StopMidi - (Paul) Stop playing current MIDI sequence

• Inputs	Outputs
  none	none

CheckMidi - (Paul) Checks to see if the Midi file is still playing, if not it calls MidiPlay
• Calls MidiPlay

• Inputs	Outputs
  none	none

Playmain - (Paul) Setup to play wav sound. Load file then place into SoundBuf.
• Requires wavfile.
• Requires fname
• Calls Initdsp, Volume, Dspwrite

• Inputs	Outputs
  wavfile	SoundBuf
  midiname	-

Settings - (Paul) Starts at the begining of the program to setup the I/O Base, IRQ, and DMA. The settings are initially set at 220h, 5, 1, but these can be modified by the user so he/she can run the program on their computer properly
• Requires I/O Base, IRQ, DMA initial settings.
• I/O Base, IRQ, DMA settings refered to as Sound settings for the rest of the functions below.

• Inputs	Outputs
  Sound settings	Sound settings

Play - (Paul) Routine for playing the sound.
• Calls Dspwrite.

• Inputs	Outputs
  Sound settings	'Sound'

Volume - (Paul) Adjusts volume for the sound to be played.

• Inputs	Outputs
  AL - 0FFh	none
  Sound Settings	none

Initdsp - (Paul) Reads from and Sets-up the DSP.

• Inputs	Outputs
  Sound Settings	none

Dspwrite - (Paul) Writes to the DSP.
• Calls MidiPlay

• Inputs	Outputs
  Sound Settings	none

Insert_Sound - (Paul)
• Requires the offset to the filename to be played.
• Calls PlayMain

• Inputs	Outputs
  AX- offset of filename	wavfile

Graphics Routines
LoadImage - (Jim) Loads an image from a file to the specified segment
• Requires a pointer to a filename
• Requires the memory location to write to

• Inputs	Outputs
  Pointer to filename containing data	-
  Memory location to write to	-

MoveSprite - (Jim) Move a sprite on the screen
• Requires the sprite number

• Inputs	Outputs
  Sprite number to draw	Draw Sprite to Screen buffer
  xlength, ylength, xstart, ystart	-

DrawTile - (Jim) Draws a sinlge tile to the screenbuffer(SBseg).
• uses JWorldVal to get sprite offset

• Inputs	Outputs
  X_cum, Y_cum	Draw Sprite to Screen buffer
  xlength, ylength, xstart, ystart	-

ShowBuffer - (Jim) Moves data from the Screen Buffer(SBseg) to the Video Memory

• Inputs	Outputs
  -	-

DrawMap - (Jim) Draws the map tiles into the screen buffer
• Requires the upper left hand position of the map array to start drawing tiles from

• Inputs	Outputs
  MAP_X and MAP_Y	Draws Map tiles on Screen buffer
  Map.dat	Updates xlength, ylength, xstart, ystart
  -	Calls DrawTile to draw each tile.

Fadeout - (Jim) Special effect to fade the screen out.(64 passes)

• Inputs	Outputs
  Palette	Pallete

DrawHealth - (Jim) Draws the player's health bar

• Inputs	Outputs
  Character	Draws health bar to the Screen Buffer

DrawAllSprites - (Jim) Draws all the active sprites onto the Screen Buffer
• Checks each sprite to see if it is in the current viewing window, if so, draw it.
• Requires MAP_X and MAP_Y

• Inputs	Outputs
  Sprites Array	xlength, ylength, xstart, ystart as inputs to a MoveSprite call
  MAP_X and MAP_Y	-

CheckScroll - (Jim) that checks to see if the screen needs to be scrolled
• Checks to see if the player is at the edge of the world -- if so, no scrolling can be done. Otherwise, Map_x=X_Pos-160, Map_Y=Y_Pos-100
.
• updates the MAP_X and MAP_Y variables.
• Call DrawMap if scrolling is needed

• Inputs	Outputs
  X_pos, Y_pos of player	MAP_X and MAP_Y
  MAP_X and MAP_Y	calls DrawMap

GamePlay Routines
WorldVal - (Nehal) Returns the value of the map array at SI.
• Requires the offset into the array in SI
• Returns the value in AX (actually only AL)

• Inputs	Outputs
  SI = offset into Map	AL = Map Value
  Keyboard Variables	-

CalculateMovement - (Nehal) Calculates a delta_x and a delta_y for the given character
• Uses Keyboard Variables
• Requires an offset to a character
• Changes that character's delta_x and delta_y

• Inputs	Outputs
  DI = Character Pointer	Updates delta_x and delta_y
  Keyboard Variables	-

ProcessMovement - (Nehal) Checks the delta_x and delta_y for a given sprite to see if it is valid
• Requires an offset to a character
• If the move is valid, resets and updates the x_pos and y_pos Also checks for walls, and does not allow movement into walls
• Calls WorldVal

• Inputs	Outputs
  DI = Character Pointer	x_pos and y_pos

ProcessBulletMovement - (Nehal) Checks to see if a bullet has hit a wall. If so, kill it.
• Requires an offset to a bullet
• Checks to see if the bullet is in a wall. If so, kill it.
• Calls Kill, WorldVal

• Inputs	Outputs
  DI = Bullet Pointer	-

InstallKBInt - (Patricia) Installs the Keyboard Interrupt handler for gameplay.
KBInt - (Patricia) Checks keyboard for valid keys, modifies variables for movement

• Inputs	Outputs
  Keyboard	Keyboard Variables(UP, DOWN, LEFT, RIGHT, F_UP, F_DOWN, F_LEFT, F_RIGHT)

RemoveKBInt - (Patricia) Removes the Keyboard Interrupt handler.
InstallTimerInt - (Patricia) Installs a timer interrupt.
TimerInt - (Nehal) Increments a variable every Timer interrupt.

• Inputs	Outputs
  Timer	Update_Positions

RemoveTimerInt - (Patricia) Removes the timer interrupt.
Enemies_Dead - (Patricia) Cycles through the Enemies array to see if anyone has died.

• Inputs	Outputs
  Enemies array	AllDead = 1 if all enemies dead

CheckHit - (Nehal) Checks to see if a bullet has hit a character. Checks to see if the bullet is within BSPACER of the character.
• Requires the bullets array
• Array of Enemies
• If the bullet has hit an enemy, decrease that character's health
• Check the enemies hit_pts. If they are less than zero, kill it.
• Kill the bullet if it hits an enemy.
• Calls Kill

• Inputs	Outputs
  Enemies array	-
  Bullet array	-

ECheckHit - (Nehal) Checks to see if an enemy is close enough (BSPACER) to a player to hurt him.
• Checks the locations around the player to see if they are inhabited by an enemy.
• If so, decrease the player's hit points.
• Calls Kill.

• Inputs	Outputs
  Enemies array	-
  Friends array	-

Attack - (Patricia) Create a bullet.
• Create a bullet whose xpos and ypos are the positions of the character, and set its direction.

• Inputs	Outputs
  DI = offset of Character	Bullet

Kill - (Nehal) Kills a character or bullet.
• Requires an offset to the object and something indicating what type of object it is.
• Plays a death sound if it is a character
• Set animation number to death sequence

• Inputs	Outputs
  AX = offset to object	-
  BX = type of object	-

EnemyMovement - (Nehal) Calcuate enemy movements
• Calculates enemy movements based on proximity to the player
• Calls Random, WorldVal, and NearFriend
• Attack a player only if he is close enough
• Attack in the direction of the player
• If the Enemy is blocked, movement has a 50% chance of moving in the previous direction, and a 50% chance of moving in either of the three other directions.

• Inputs	Outputs
  DI = offset to enemy	delta_x and delta_y

Random - (Patricia) A random number generator
• Generates a random number based on the last number generated.
• According to the same formula used in MP3

• Inputs	Outputs
  Seed	Random number

NearFriend - (Nehal) Checks to see if the enemy is within a certain distance (ATTACK_BUFFER) of the player.
• Requires an Enemy Pointer in DI, and returns the Friends index into the Friends array + 1 in AX.

• Inputs	Outputs
  DI = Enemy Pointer	AX = Friends Array offset + 1 of nearest friend

Initialize_Sprites - (Nehal) Initializes the objects of the game.
• The player starts at a certain position.
• Initializes enemies with random positions, but checks to make sure that they don't start in a wall, and they do not start too close to the player. initializes last 20 enemies with 0 hit_pts
• Starts all bullets with time = 0

• Inputs	Outputs
  Friends, Enemies, Bullets arrays	Friends, Enemies, Bullets arrays

SinglePlayerGame - (Nehal) Main loop for the game. Draw the screen, update the positions, check for quit or death flags, and exit if necessary.
• Update positions every timer interrupt.
• Draw the screen as often as possible
• Check CARTMAN_DEAD, AllDead, and EXIT_GAME to exit loop.

• Inputs	Outputs
  -	-