{
The Following code is a little cheeze example of getting around the ye ol'
retrace and flicker problem. To do this all writes are made to a vitual
screen and then the whole thing is moved at once. This code has quite a
nice effect even though it almost all in pure pascal.
}

{\$q-,r-,d-,b-}

PROGRAM game_sprites;
{ Slow game-sprites-example, by Bas van Gaalen, Holland, PD }
{12/20/94}
{ Modified and completely rewritten by Mr. Krinkle : Cameron Clark}
USES crt;
CONST  maxSpr=110;                         {Reduce, if program runs slugish}
ScrSze=64000;
TYPE a_scrn= ARRAY [1..ScrSze] OF byte;
sprite= RECORD
xCOR,  yCOR   : word;
width, height : byte;
vVEL,  hVEL   : word;
it: ARRAY[1..500]  OF byte;   {bitmap}
END;
VAR sprites : ARRAY[1..MaxSpr] OF sprite;
point1 : Pointer;
point2 : ^a_scrn; {Used for screen math}
i,j,k  : word;
PROCEDURE setpal(col,r,g,b : byte); assembler; ASM
mov dx,03c8h; mov al,col; out dx,al; Inc dx; mov al,r
out dx,al; mov al,g; out dx,al; mov al,b; out dx,al; END;

PROCEDURE putsprite( VAR spriter : sprite );
VAR i : word;
BEGIN {Update coordinates according to H&V velocity and virtual draw}
WITH Spriter DO BEGIN
IF  (xCOR + hVEL > 320 - width)  OR (xCOR + hVEL < 1) THEN
hVEL:=hVEL * -1;
IF  (yCOR + vVEL > 200 - height) OR (yCOR + vVEL < 1) THEN
vVEL:=vVEL * -1;
xCOR:=xCOR + hVEL;  yCOR:=yCOR + vVEL;
FOR i:=0 TO (width * height)-1 DO
IF  it[i+1] <> 0 THEN
Point2^[(yCOR + (i DIV width)) * 320 +
xCOR + (i MOD width)]:= it[i+1];
END;
END;

BEGIN {*Skeleton*}
ASM mov ax,13h; Int 10h; END;
FOR i:=1 TO 255 DO setpal(i,255-i DIV 6,255-i DIV 4,50);
{ create and save background }
FOR i:=0 TO (320*200)-1 DO mem[\$a000:i]:=random(50)+200;
GetMem(Point1, ScrSze);
GetMem(point2, ScrSze);
Move(mem[\$a000:0000], Point1^, ScrSze);
Randomize;  { create random sprite }
FOR J:=1 TO MaxSpr DO BEGIN
sprites[j].xCor := random(300)+1;  {Screen Pos}
sprites[j].yCor := random(170)+1;
sprites[j].width := random(15)+5;  {Dimensions}
sprites[j].height := random(15)+5;
sprites[j].hVEL := 6-random(16);   {horiz. sprite displacement}
sprites[j].vVEL := 6-random(13);   {Vert.  sprite displacement}
K:=random(5)+1;
FOR i:=1 TO sprites[j].width * sprites[j].height DO BEGIN
IF I DIV k = i / k THEN sprites[J].it[I]:= I MOD 255;
END;
END;
REPEAT
Move(Point1^, Point2^, ScrSze);         {copy Background for writing on}
FOR J :=1 TO MaxSpr DO BEGIN
putsprite( sprites[J] );             {virtual write to Point2}
END;
Move(point2^, mem[\$a000:0000], ScrSze); {write Point2}
UNTIL KeyPressed;                         {NO retrace needed}
ASM mov ax,03h; Int 10h; END;
END.

{ASM rewrite for putSprite requested! Update it for us poor ASM
illiterates!}