Started this in TASM but switched to FASM because I really should make some kind of attempt to update myself. Originally 170-something bytes, took some work getting it down to 159. Remove the text, pallete rot and exit logic and it should be 97 bytes.
boogop greets: ralf brown's interrupt list lol
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;▒ 10/2018 by Boogop
;▒ Boring Old Fire in 159 bytes
;▒
;▒ Acknowledgements:
;▒ - raven/tektonic,preacher/traction and others for
;▒ the adc idea, really makes it look demo-y
;▒
;▒ requirements
;▒ - must have a halloween message referencing dbf
;▒ - fire must not look like suck
;▒ - text shouldn't be white
;▒ - must have appropriate exit logic
;▒
;▒
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org 100h
use16
; in command.com we trust
; assume ax = 0, if not we're in trouble ;)
mov al,13h ; enter classic demo world
int 10h
xchg al,ah ; al=13h,ah=0 after setting video mode. Switch those
; to get the draw string function in ah and save 2 bytes
; setting al=0 uses color attributes in bl
; draw text
mov bl,128 ; color index, we'll rotate it later
mov cl,24 ; string length
mov dx,0107h ; dl=7 dh=1 column 7 row 1
mov bp,foo
int 10h
; set palette
xor ax,ax
mov dx, 3c9h ; who needs 3c8h!
@redup: ; Set colors 0-64, ramp up red
out dx,al ; set red to value in al
xchg al,ah ; green & blue get 0
out dx,al ; the xchg commands seem unavoidable
out dx,al
xchg al,ah
inc ax ; 1 byte smaller than inc al
cmp al,64
jne @redup
@yellowdn: ; we'll add some yellow for the lols
out dx,al
out dx,al
xchg al,ah
out dx,al
xchg al,ah
dec ax
jnz @yellowdn ; don't need cmp al,0
push 0a000h ; ds:si is smaller than es:di
pop ds ; by about 6 bytes it seems (why??)
@main:
; fire
mov si,(199*320) ; bottom line, y * xres
mov cx,320 ; screen_w
@randline:
in al,40h ; the better looking prods tend to use
; rng's, but for my purposes 40h does
mov [ds:si],al ; just fine
inc si ; using the ds: prefix isn't necessary
loop @randline ; but makes things a little clearer
mov si,(320*20) ; we're moving forwards through video
; memory, some move backwards. Skip the
; first 20 lines for the text so it doesn't
@draw: ; melt
mov al,[ds:si] ; add the surrounding pixels
shl ax,2 ;
add al,[ds:si+1] ;
adc ah,0 ; if the carry flag is set, add 1 to ah
add al,[ds:si+320] ;
adc ah,0 ;
add al,[ds:si-1] ;
adc ah,0
add al,[ds:si+640] ; add the pixel 2 rows above for higher flame
adc ah,0 ; ah += 0 + cf
shr ax,3
;or ax,00111101b ; uncomment for weird effect lol
; don't let al wrap, you get lots of
jz @nozero ; noise on the screen
dec ax
@nozero:
mov [ds:si-320],al ; put the pixel back on the row below
inc si
jnz @draw ; if it's wrapped to 0 we've reached the end of the screen
inc bh
mov dx,3C8h
mov al,128 ; rotate palette index 128
out dx,al
inc dx
mov al,bh ; increment red & green together
out dx,al
out dx,al
sub al,32 ; stick blue 32 behind them for great justice
out dx,al ; we could save 2 bytes by making it white but
; that looks like crap
in al,60h ; check keypress
dec ax ; escape key = 01h, dec 01h = 0
jnz @main ; dex ax one byte smaller than dec al
; exit stuff
mov al,03h
int 10h
ret
foo db 'Halloween greets to DBF!'
