.model small
.stack 256h
.386
video equ 0b800h
;-----------------------------------
; STANDARD 4-bit COLOR DEFINITIONS
;-----------------------------------
black        = 0
blue         = 00010001b
green        = 00100010b
cyan         = 00110011b
red          = 01000100b
magenta      = 01010101b
brown        = 01100110b
lightGray    = 01110111b
gray         = 10000111b
lightBlue    = 10011001b
lightGreen   = 10101010b
lightCyan    = 10111011b
lightRed     = 11001100b
lightMagenta = 11011101b
yellow       = 11101110b
white        = 11111111b
ESCKEY =27
spacebar =32
.data
save_di word ?
incr word 1
bullet word 0
bpos word 5 dup (0)
.code

start proc near
	mov ax, @data
	mov ds, ax
	mov ax, video
	mov es, ax
	mov ax, 4
	int 10h         ;sets at medium resolution
        mov ah, 0ch
	int 21h
	
	xor si, si
	xor dx, dx

call paint_back;;; paint the entire screen green

mov di, 4    ;to begin the figure at the first even line

redraw:	
mov save_di,di


call drawalien;;draws alien in magenta and black
	
	mov  ah,11h	; key pressed already?
	int  16h
	jz   L2          	; no, continue the loop
	mov  ah,10h	; remove key from buffer
	int  16h
	cmp  al,ESCkey   	; yes. Is it the ESC key?
	cmp  al,spacebar
	je   dosret        	; yes, quit the program
L2:
mov cx,100
again:
   call slow
loop again
call paint_over		;;redo background just in the spot alien was drawn

mov di,save_di
add di,incr


;cmp di,10
;jle cont
;cmp di,4
;jge cont
;neg incr

	
cont:	
jmp redraw
	
	dosRet:
	
		mov ax, 2
		int 10h
		mov ax, 4c00h
		int 21h
	
	start endp
slow proc
pusha
mov cx,32000
slow1:
pusha
popa
loop slow1
popa
ret
slow endp
paint_back proc
	
	
	xor di, di     ;start di at first even line
	mov cx,1f40h   
	mov al, 0aah
	rep stosb
	mov di, 2000h
	mov cx,1f40h
	rep stosb
	
ret
paint_back endp

drawalien proc
        mov al,magenta
	mov di,save_di          ;restore the starting position
	        
	mov cx, 1
	rep stosb       ;second even line
	add di, 78
	mov cx, 3
	rep stosb
	add di, 76   ;third even line
	stosb
	mov al,black
	stosb
	mov al,magenta
	stosb
	mov al,black
	stosb
	mov al,magenta
	stosb
	add di, 75   ;fourth even line
	
	mov cx, 5
	rep stosb
	add di, 76
	mov al,black
	mov cx, 3
	rep stosb
	mov al,magenta
	add di, 77
	mov cx, 3
	rep stosb

	mov di,save_di
	add di, 2000h  ;first odd line
	mov cx, 1
	rep stosb
	add di, 78 ;second odd line
	mov cx, 3
	rep stosb
	add di, 76   ;third odd line
	mov cx, 1
	stosb
	mov al,black
	stosb
	mov al,magenta
	stosb
	mov al,black
	stosb
	mov al,magenta
	stosb
	
	add di, 75   ;4th odd line
	mov cx, 5
	rep stosb
	
	add di, 76
	mov cx, 3
	mov al,black
	rep stosb
	add di, 77	
	mov al,magenta
	mov cx, 3
	rep stosb
	ret
	drawalien endp
	
	
	paint_over proc
	
	mov al, 0aah
	mov di,save_di          ;restore the starting position

	
		        
		mov cx, 1
		rep stosb       ;second even line
		add di, 78
		mov cx, 3
		rep stosb
		add di, 76   ;third even line
		stosb
		;mov al,black
		stosb
		;mov al,magenta
		stosb
		;mov al,black
		stosb
		;mov al,magenta
		stosb
		add di, 75   ;fourth even line
		
		mov cx, 5
		rep stosb
		add di, 76
		;mov al,black
		mov cx, 3
		rep stosb
		;mov al,magenta
		add di, 77
		mov cx, 3
		rep stosb
	
		mov di,save_di
		add di, 2000h  ;first odd line
		mov cx, 1
		rep stosb
		add di, 78 ;second odd line
		mov cx, 3
		rep stosb
		add di, 76   ;third odd line
		mov cx, 1
		stosb
		;mov al,black
		stosb
		;mov al,magenta
		stosb
		;mov al,black
		stosb
		;mov al,magenta
		stosb
		
		add di, 75   ;4th odd line
		mov cx, 5
		rep stosb
		
		add di, 76
		mov cx, 3
		;mov al,black
		rep stosb
		add di, 77	
		;mov al,magenta
		mov cx, 3
		rep stosb
	
	ret
	paint_over endp
end start