Нарисовать облачко, плывущее по небу и периодически закрывает солнце

uses graphABC, crt;
type mas=array [1..1000] of integer;
var i,kox,koy: integer;
    a,b: mas;
 
procedure fon (a,b: mas);
var i,x,y: integer;
begin
setbrushcolor(clnavy);
setpencolor(clnavy);
rectangle(0,0,800,200);
setbrushcolor(clblue);
setpencolor(clblue);
rectangle(0,200,800,400);
setbrushcolor(clgreen);
rectangle(0,400,800,600);
setpencolor(cllime);
for i:=1 to 1000 do
    line(a[i],b[i],a[i]+(random(11)-5),b[i]-(random(11)+10));
setpencolor(clblack);
setbrushcolor(clyellow);
circle(700,100,40);
end;
 
procedure Oblako(var x,y: integer);
var j: byte;
begin
setpencolor(clskyblue);
setbrushcolor(clskyblue);
for j:=1 to 4 do
    begin
    circle(kox,koy,random(20)+35);
    circle(kox-40,koy,random(20)+35);
    circle(kox+40,koy,random(20)+35);
    end;
setpencolor(clwhite);
setbrushcolor(clwhite);
for j:=1 to 4 do
    begin
    circle(kox,koy+20,random(10)+15);
    circle(kox-30,koy+20,random(10)+15);
    circle(kox+30,koy+20,random(10)+15);
    end;
end;
 
begin
for i:=1 to 1000 do
    begin
    a[i]:=random(800);
    b[i]:=random(201)+400;
    end;
setwindowsize(800,600);
lockdrawing;
hidecursor;
kox:=-100;
koy:=100;
repeat
for i:=1 to 50 do
    begin
    clearwindow;
    fon(a,b);
    Oblako(kox,koy);
    sleep(100);
    redraw;
    if kox>900 then kox:=-100
       else kox:=kox+10;
    end;
until keypressed;
end.