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    {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.
     Enjoy: Swag ready. [g]}
    {$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.

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