Броуновское движение (задача на графику с анимацией)

uses graphABC,crt;
var x,y,x0,y0: integer;
begin
setwindowsize(700,500);
hidecursor;
x:=random(701);
y:=random(500);
setpencolor(clblue);
setbrushcolor(clblue);
SetPenMode(pmNot);
circle(x,y,2);
repeat
if (x<680) and (x>20) then x:=x+(random(3)-1) else
   if x>680 then x:=x+(random(3)-3) else x:=x+(random(3));
if (y<480) and (y>20) then y:=y+(random(3)-1) else
   if y>480 then y:=y+(random(3)-3) else y:=y+(random(3));
circle(x,y,2);
sleep(1);
until keypressed;
end.

uses graphABC;
var x,y,x0,y0: integer;
begin
setwindowsize(700,500);
x:=random(701);
y:=random(500);
setpixel(x,y,clBlue);
repeat
if (x<680) and (x>20) then x:=x+(random(3)-1) else
   if x>680 then x:=x+(random(3)-3) else x:=x+(random(3));
if (y<480) and (y>20) then y:=y+(random(3)-1) else
   if y>480 then y:=y+(random(3)-3) else y:=y+(random(3));
setpixel(x,y,clBlue);
sleep(1);
until false;
end.

uses graphABC;
var f:boolean;
procedure KeyPress(key:char);
begin
if key<>#0 then f:=false;
end;
var x,y,x0,y0: integer;
begin
setwindowsize(700,500);
x:=random(701);
y:=random(500);
f:=true;
onkeypress:=KeyPress;
setpixel(x,y,clBlue);
repeat
if (x<680) and (x>20) then x:=x+(random(3)-1) else
   if x>680 then x:=x+(random(3)-3) else x:=x+(random(3));
if (y<480) and (y>20) then y:=y+(random(3)-1) else
   if y>480 then y:=y+(random(3)-3) else y:=y+(random(3));
setpixel(x,y,clBlue);
sleep(1);
until f=false;
end.