Elysian Shadows

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;------------ INITIALIZATION -----------;

VSeg EQU 0A000h

JMP start

OldVidMode	DB ?
PaddleX	DW 160
BallX		DW 160
BallY		DW 100
BallDX	DW 1
BallDY	DW -1
BallCounter DB 3
start:

; Store old video mode
MOV AX, 0F00h
INT 10h
MOV OldVidMode, AL

; Set new video mode
MOV AX, 0013h
INT 10h

CALL Main

;CALL WaitKey

; Restore old video mode
MOV AH, 00h
MOV AL, OldVidMode
INT 10h

; Terminate program
MOV AX, 4C00h
INT 21h


;----------- SUBROUTINES ----------;


WaitKey:
MOV AH, 06h
MOV DL, 0FFh
WK_loop:
INT 21h
JZ WK_loop
RET


Main:

;MOV AX, 0001h
;INT 33h

MOV AX, 000Bh
INT 33h

MainLoop:

CALL Update

CALL ClearBuf
CALL Draw
CALL Blit

; Check for a keystroke
MOV AH, 06h
MOV DL, 0FFh
INT 21h
JZ MainLoop ; No Keystroke? Jump to start

RET

ClearBuf:
MOV CX, 320 * 200 
MOV ES, CS
MOV DI, OFFSET VidBuf
CLD
MOV AL, 0
REP STOSB
RET

Blit:
MOV CX, 320 * 200 
MOV ES, VSeg
MOV DI, 0
MOV DS, CS
MOV SI, OFFSET VidBuf
CLD
REP MOVSB
RET

Draw:

; Draw player paddle
MOV AX, PaddleX
MOV BX, 64000 - 960
CALL DrawPaddle

; Draw Computer paddle
MOV AX, BallX

CMP AX, 16
JGE PaddleLeftGood
MOV AX, 16
PaddleLeftGood:

CMP AX, 320-16
JLE PaddleRightGood
MOV AX, 320-16
PaddleRightGood:

MOV BX, 0
CALL DrawPaddle

; Draw Ball
CALL DrawBall

RET


DrawPaddle:
MOV ES, CS
MOV DI, OFFSET VidBuf
ADD DI, AX
SUB DI, 16
ADD DI, BX
MOV CX, 32
MOV AL, 2
REP STOSB
MOV CX, 32
ADD DI, 320 - 32
REP STOSB
MOV CX, 32
ADD DI, 320 - 32
REP STOSB
RET

DrawBall:
MOV ES, CS
MOV DI, OFFSET VidBuf
MOV AX, BallY
IMUL AX, 320
ADD AX, BallX
ADD DI, AX
SUB DI, 320 + 1

MOV CX, 3
MOV AL, 3
REP STOSB
MOV CX, 3
ADD DI, 320 - 3
REP STOSB
MOV CX, 3
ADD DI, 320 - 3
REP STOSB
RET

Update:

; ------ Upate Player Paddle ------ ;

; Get Relative Mouse movement
MOV AX, 000Bh
INT 33h
ADD PaddleX, CX

CMP PaddleX, 16
JGE NoFixRight
MOV PaddleX, 16
NoFixRight:
CMP PaddleX, 320 - 16
JLE NoFixLeft
MOV PaddleX, 320 - 16
NoFixLeft:

DEC BallCounter
CMP BallCounter, 0
JZ BallNeedUpdate
RET
BallNeedUpdate:
MOV BallCounter, 3

; ------- Update Ball --------------- ;
MOV AX, BallX
ADD AX, BallDX
MOV BallX, AX

MOV AX, BallY
ADD AX, BallDY
MOV BallY, AX

CMP BallX, 1
JGE BallLeftGood
MOV BallX, 1
NEG BallDX
BallLeftGood:

CMP BallX, 320-1
JLE BallRightGood
MOV BallX, 320-1
NEG BallDX
BallRightGood:

CMP BallY, 4
JGE BallTopGood
MOV BallY, 4
NEG BallDY
BallTopGood:

CMP BallY, 200-4
JLE BallBotGood

MOV AX, BallX
SUB AX, PaddleX
CMP AX, 18
JLE NotMissedRight
CALL ResetBall
JMP BallBotGood

NotMissedRight:
CMP AX, -18
JGE DoneBall
CALL ResetBall
JMP BallBotGood

DoneBall:
MOV BallY, 200-4
NEG BallDY
BallBotGood:

RET

ResetBall:
MOV BallX, 160
MOV BallY, 100
MOV BallDX, 1
MOV BallDY, -1
RET

VidBuf DB