About Frogger

How the Game Works

Please type in "frogger" after compiling This is a two player game. One of the players being an Arificially intelligent frog. The AI frog will start on the screen opposite to the frog played by the human player. The object of each frog is to get to the other side. The Screen that they have to cross is 200 by 640 screen. There is one median You use the keyboard to get across. Additionaly, the user can select the how "smart" the frog can think. This option "speed" will actually determine how fast the frog can "think." The AI frog will get dummer and smarter depending on how close the user is to reaching the other side. Both of the Frogs have three lives. But the game only terminates when the user has died three times.

Data Structures
AI Variables and constants:

AIPANIC How well AI Frog does in a panicky situation
AISMARTNESS This is the default intelligence of the frog.
DUMTHRESH How dumb the frog is (a range)
SMARTTHRESH How smart a frog can be (a range)
SPEED to set the intelligence of the AI frog
AIDEBUG used for checking the right SEG (where the AI frog is)
FROG2_ROW Used for the AI frog. Position Var.
FROG2_COLUMN Same as above.
AI_ENABLED (want our frog thinking)
AI_KNOWS (doesn't know log direction initially)
AI_THINKING (starts off not thinking)
MAX_INTELLIGENCE AISMARTNESS ;(try different values)
THOUGHT_STEP

PgPort equ 83h
AddPort equ 02h
LenPort equ 03h
ModeReg equ 49h
Channel equ 01h
BasePort equ 220h
Freq equ 11000

Length1 Length of a DMA buffer
MemLoc Used by PlayWAV
Page1 Used by a PlayWAV
OUND_BACK To turn sound on and off
Buffer Used by DMA
DataA Size of the buffer

SCOREOFFSET offset of the place where the score is displayed
SCORE Used for the Human frog
SCORE2 Used for the AI frog
FROG_ROW Row of Frog
FROG_COLUMN Column of Frog
NEW_ROW Passed in to Valid Move to see if the move was valid.
NEW_COLUMN Same as above
LIVES the number of lives of the UnAI frog.
LIVES2 the " " " "" " " " " AI frog.
WhichDraw1 Used in DrawFrog to determine which frog should be on the screen
WhichDraw2 '' '' '' '' '' '' '' '' '' ''

Intro Animation Vars
tmpWd dw ?
tmpHt dw ?
minus_1 REAL4 -1.0
pos_1 REAL4 1.0
Animscale REAL4 1.50 ;initial scaling amnt
Animdelta REAL4 0.00390625 ;initial change in scaling (delta scale)
Animaxel REAL4 0.0001 ;change in change scaling (delta delta scale)
thirtytwo REAL4 32.0
twenty REAL4 20.0
two REAL4 2.0
pal_buf db 768 dup (0) ;buffer to temporarily hold palette
buffer1 dw ?
Intro db 'intro.pcx', 0 ; Path & Filename of frogger picture
Puff db 'puff.xmi',0 ; frog xmi file to be played by midpak
frogavi db 'grafx/frogavi/frog000.PCX',0

GamePlay AnimationVars
QUARTER Holds which quarter of the PlayingField will be shown on the Left hand side of the screen. 1,2,3 would be the values.
PREVQUARTER to determine which way the screen shifts. Used by UpdateScreen. Compares with QUARTER.
Whichoffset dw 0,33,66,99,132 Used to find out where the info for each column started
dw 165,198,231,264,297
dw 330,363,396,429,462
dw 495,528,561,594,627

COLUMN STRUC ; Information stored in this structure takes uop the next ; four bytes.
COL_NUMBER db ? ; number of columns -- start ; at 3rd? column
COL_SPEED db ? ; speed of column ? 1
COL_SPACING db ? ; spacing number for next object ; Random
COL_CURR_OBJ db ? ; object being moved into column
COL_PHASE db ? ; 0=display, 1=spacing, 2=get new ; object
COL_DIRECTION db ? ; 1=up, 0=down
COL_SCREENOFFSET dw ? ; where column starts
COL_VALUES db 24 dup (0) ; says whether an object
; is in that pixel, 0 denotes ; no, 1 denotes yes
COL_ROW_NUM db 0 ;Initially set to 0, this is used
; to find out what's been printed already.
COLUMN ENDS
OBJECT STRUC
NUM_OBJ db ? ;What object is it 0 IS BLANK 1,2,3,4 ARE OBJECTS
LENGTH_ofObj db ? ; Length of the object, random
OFFSET_ofObj dw ? ; Hmmmmmmm
OBJECT ENDS
Same reason as for WhichOffset, but for the Object Struc
WhichObjOffset dw 0, 4, 8, 12, 16, 20, 24, 28, 32;, 36;, 40, 44, 48
; Info for each column this is the struc which saves this info.
COLUMNS COLUMN<0, 0, 1, 0, 0, 0, 0, 000000000000h, 0> ;0
COLUMN<1, 0, 1, 0, 0, 1, 1*32, 000000000000h, 0> ;33
COLUMN<2, 0, 1, 0, 0, 0, 2*32, 000000000000h, 0> ;66
COLUMN<3, 0, 1, 0, 0, 1, 3*32, 000000000000h, 0> ;99
COLUMN<4, 0, 1, 0, 0, 0, 4*32, 000000000000h, 0> ;132
COLUMN<5, 0, 1, 0, 0, 1, 5*32, 000000000000h, 0> ;165
COLUMN<6, 0, 1, 0, 0, 0, 6*32, 000000000000h, 0> ;198
COLUMN<7, 0, 1, 0, 0, 1, 7*32, 000000000000h, 0> ;231
COLUMN<8, 0, 1, 0, 0, 0, 8*32, 000000000000h, 0> ;264
COLUMN<9, 0, 1, 0, 0, 0, 0, 000000000000h, 0> ;297
COLUMN<10, 0, 1, 0, 0, 0, 0, 000000000000h, 0> ;330
COLUMN<11, 0, 1, 0, 0, 1, 1*32, 000000000000h, 0> ;363
COLUMN<12, 0, 1, 0, 0, 0, 2*32, 000000000000h, 0> ;396
COLUMN<13, 0, 1, 0, 0, 1, 3*32, 000000000000h, 0> ;429
COLUMN<14, 0, 1, 0, 0, 0, 4*32, 000000000000h, 0> ;462
COLUMN<15, 0, 1, 0, 0, 1, 5*32, 000000000000h, 0> ;495
COLUMN<16, 0, 1, 0, 0, 0, 6*32, 000000000000h, 0> ;528
COLUMN<17, 0, 1, 0, 0, 1, 7*32, 000000000000h, 0> ;561
COLUMN<18, 0, 1, 0, 0, 0, 8*32, 000000000000h, 0> ;594
COLUMN<19, 0, 1, 0, 0, 0, 0, 000000000000h, 0> ;627

; This is the struc for al the different objects and their offsets
OBJECTS OBJECT<0, 0, 0> ; This represents a blank.
OBJECT<1, 18, 27> ; Short Log
OBJECT<2, 36, 17600> ; Long Log
OBJECT<3, 54, 5787> ; Gator
OBJECT<4, 36, 5760> ; Turtle
OBJECT<5, 18, 27> ; Short Log
OBJECT<6, 36, 17600> ; Long Log
OBJECT<7, 18, 27> ; Short Log
OBJECT<8, 36, 17600> ; Long Log
OBJECT<9, 18, 27> ; Short Log
OBJECT<10, 36, 17600> ; Long Log


NextCOLinScrSEG dw ? Used by Animate Object
Mouse Variables
the following will all have constant values to specify which area has been clicked on
PLAYERCLK
STARTCLK
SOUNDCLK
SPEEDCLK
SCENARIOCLK
HIGHSCORECLK
EXITCLK

SEGMENTS
LeftSEG1 Hold Lefthand side of 640x200 playing fieldd. RightSEG2 Holds Right hand side of field. LeftBackSeg Used for the background ScrSeg Genereal Purpose Segment used for Everything from saving scores to Scrolling Screens TextureSeg This is where the objects and background are stored AviSeg Used for animation FrogXmi " " " SBSeg Used by DrawPic to update the screen.

Main
Purpose: This displays what is shown at the beginning of the game. It gives you a selection of choices, such as Number of
Players, Sound, Speed, Scenarios, High Scores, Start and Exit the game. It will be controlled by mouse selection.
Inputs: Mouse
Outputs: Update changed variables(Sound, Players, Speed, Scenario) according to the Mouse Click
Updates the screen according to the changed variables
Calls:
Mouse Interrupt
LoadPCX
HighScore
PlaySound
Purpose: To play WAV files.
Inputs: Play Wave takes an offset to a string of the Wav file you want to play.
Outputs: Plays the Wav
Updates:
Calls: Next four
DMAPlay
Purpose: Programs the DMA to play contents in buffer (containing wav file)
Inputs: dma channel, and various other sound card constants
Outputs: instructs Dma to transfer information
Updates: nothing
Calls: none
MstrVol
Purpose: Sets card's wave volume to maximum Inputs: various sound card constants (Base Address, etc.)
Outputs: maximizes wave volume
Updates: volume of wave playback
Calls: none

ResetDSP:
Purpose: Resets the Dsp of the soundcard
Inputs: Base i/o address of sound card
Outputs: resets sound card
Updates: soundcard
Calls: port calls to sound card

WriteDSP:
Purpose: handles writes to DSP
Inputs: Base i/o address of sound card
Outputs: none
Updates: sound card DSP
Calls: port calls to sound card

DrawStrip2:
Purpose: Scales strips from source image to screen (using Bresenham algorithm)
Inputs: Height of strip, Horizontal position of strip, strip number and destination segment
Outputs: draws strip to segment
Updates: updates target segment
Calls: none

ScaleBMP2:
Purpose: Uses DrawStrip2 to scale entire bitmap onto avidseg
Inputs: destination height and width of source bitmap
Outputs: scales bitmaap to avidseg
Updates: aviseg
Calls: DrawStrip2
ReadPalette:
Purpose: Reads palette entries (RGB) into a buffer
Inputs: buffer to store palette entries
Outputs: stores palette entries into buffer
Updates: pal_buf
Calls: interrupts to read palette entries
FadeOut2:
Purpose: decreases RGB values of palette entry until R = G = B = 0 (black)
Inputs: pal_buf
Outputs: writes new values to palette
Updates: changes palette
Calls: port calls to video card (to update palette)
PlayMIDI:
Purpose: Loads and Plays specified MIDI file (.xmi)
Inputs: FrogXmi (segment containing xmi data)
Outputs: Playes .xmi file contained in segment
Updates: Soundcard
Calls: int 66 (midpaks interrupt)
swapframe:
Purpose: Swaps appropriate frame of animation to Aviseg
Inputs: Frame number to display
Outputs: updates AviSeg
Updates: updates AviSeg
Calls: loadpcx, binasc
SetUpGameData
Purpose: This initializes the variables to their defaults.Calls Sets up initial Playing field.
Inputs:
SCORE = 0
PLAYERS = 1 1 SPEED = 0 SCENARIO = 0 FROG_ROW = 0
Outputs: Initial Screen.
Calls: LoadPCX twice, Randomizer. DrawFrog

Keyboard Interrupt
Purpose: Replace default keyboard interrupt routine.
Inputs: Button Presses
Outputs:
MOVE_RIGHT set to 1 if right arrow pushed
MOVE_LEFT set to 1 if left arrow pushed
MOVE_UP set to 1 if up arrow pushed
MOVE_DOWN set to 1 if down arrow pushed
Exits to Main Menu if ESC pushed
Calls: None
MouseControl
Purpose: To get user input via the mouse
Inputs: None
Outputs: Returns values according to below

VALUE:
PlayerClk = players clicked
StartClk = start clicked
SoundClk = sound clicked
SpeedClk = speed clicked
ScenarioClk = scenario clicked
HighScoreClk = high score clicked ExitClk = exit clicked
Calls: None
LoadPCX
Purpose: Loads and decodes a 320x200 PCX file into memory and sets VGA Palette registers to those used by the image.
Fills VGA palette registers with image colors
Uses ScratchPad to hold compressed image data
Inputs:
ax = Destination segment address.
dx = pointer to a null-terminated string containing the filename
Outputs: Fills destination (DestSeg:0) with image data.
RandomNumber
Purpose: Generate a random number for use in delay and choice of object
Inputs: None
Outputs: ax = random number
Calls: Nothing
DrawPic
Purpose: to draw the future screen called by UpdateScreen and AnimateObject
Inputs: ah
Outputs: Updated Screen in ScrSEG
Calls: None
AnimateObject
Purpose:This function controls the animation of all of the objects in the water and roads, doing this by column. It keeps each column's info in the Column structures
Inputs: Column structures, objects
Outputs: Updated column structures, Updated the Screen
Calls:
helper functions
MoveUp Movesup each column starting from it's offset
MoveDown Movesdown each column based on it's offset
ShiftRight Shifts A 24 byte Array(192 bits) Right
ShiftLeft Shifts " " " "

RandomNumber
DrawPic ; to update the screen.

MoveFrog
Purpose: This function moves the position of the frog. Frog reaches half way to the screen, it calls UpdateScreen to shift screen right by one quarter, i.e. 160 pixels. Updates FROG_ROW and FROG_COLUMN accordingly.
Inputs: Key presses and variable values
Outputs: New FROG_ROW and FROG_COLUMN values according to the arrow press QUARTER
Calls: ValidMove to check to see if the frog is actually still alive with those new values
UpdateScreen.
ValidMove
Purpose:This function checks to see if the move of the frog is valid, i.e., does the frog die. If the frog tries to move off of the screen, he is also considered dead.
Inputs:FROG_ROW, FROG_COLUMN
Outputs:1 if move valid, 0 if the move is invalid
Calls:Nothing
Must check boundaries
Checks column structure to see if frog will be on a valid object or not
DrawFrog
Purpose: This function actually draws the frog after the move has been validated and the position of the frog has been updated. Draws both the artificially intelligent and the naturally intelligent frog.
Inputs: FROG_ROW, FROG_COLUMN, FROG_ROW2, FROG_COLUMN2, Quarter, WhichDraw1, WhichDraw2
Outputs: New drawn frog on screen
Calls: Nothing
UpdateScreen
Purpoxe: This procedure will shift the screen by 160 pixels to the right or left depending on what the future quarter is and the Previous quarter was.
Inputs: QUARTER, PREVQUARTER
Outputs: Shifting Screen
Calls: Nothing.
ShowHigh
Purpose: To show the high scores.
Inputs: highsc (name of file)
Outputs: The list of scores
Calls: Lib291Routines Install/Deinstall key.
AIEngine
Purpose: This takes care of the Artificially Intelligent frog
Inputs: FROG2_ROW, FROG2_COLUMN, AI_ENABLED, DUMTHRESH, MAX_INTELLIGENCE, SMARTHRESH, AI_THINKING, AI_KNOWS
Outputs: Info for the other frog.
Calls: Random, ValidMove
Additional info . DrawChar1
Purpose: Draws a digit of the score on the screen. Offsets are given in.
Inputs: ULSOURCE, ULDEST.
Outputs: Output displayed to the screen.
Calls: none.
CMDlineparse
Purpose: Used for demoing. Reads instructions from command line. Used as backup. Used for seeing the other side fo the screen.
Inputs: text from screen.
Outputs: Altered copy of game to screen.
Calls: none
ShowHighScore
Purpose: To find out the Score and have it printed on either side of the screen. Converting from Hex to ascii
Inputs: SCORE, SCORE2
Outputs: The score of both frogs on the right and left side of the screen.
Calls: DrawChar1