uses graph,crt;
label 1,2;
var a,d,m,pX,pY,S,vS,X,Y,vX,vY,rX,rY,Dy : Integer;

begin
S:=2; X:=1; Y:=1; vX:=1; vY:=1; rX:=1; rY:=1; vS:=2; Dy:=10;
randomize;
d:=VGA; m:=2;
initgraph(d, m, 'c:\bp\bgi');
setColor(5);
For pX:=1 to 3 do
For pY:=1 to 4 do
Rectangle(pX*50,pY*50,pX*50+35,pY*50+35);
SetColor(7);
Rectangle(35,35,201,251);
setcolor (0);
line(35,251,50,251);
setcolor (7);
line(35,251,35,270);
line(50,251,50,270);

repeat
1:
if S=2 then vS:=Random(3)+1;
if S=3 then vS:=Random(3)+2;
if S=4 then
 begin
  vS:=Random(3)+1;
  Case vS of
  1 : vS:=1;
  2 : vS:=3;
  3 : vS:=4;
  end;
 end;
if S=1 then
 begin
  vS:=Random(3)+1;
  Case vS of
  1 : vS:=1;
  2 : vS:=2;
  3 : vS:=4;
  end;
 end;

Case vS of
  1 : if vX>1 then Dec(vX);
  2 : if vY<5 then Inc(vY);
  3 : if vX<4 then Inc(vX);
  4 : if vY>1 then Dec(vY);
  end;

if (X=1) and (Y=5) and (vS=4) then goto 2;
if (X=vX) and (Y=vY) then goto 1;
X:=vX;  Y:=vY;  S:=vS;

if S=3 then
 begin
  For a:=rX*50 to X*50 do
    begin
      SetColor(15);
      Circle(a-7,Y*50-6,5);
      Delay(Dy);
      SetColor(0);
      Circle(a-7,Y*50-6,5);
      SetColor(2);
      Circle(3*50-7,3*50-6,5);
    end;
 end;

if S=1 then
 begin
  For a:=rX*50 downto X*50 do
    begin
      SetColor(15);
      Circle(a-7,Y*50-6,5);
      Delay(Dy);
      SetColor(0);
      Circle(a-7,Y*50-6,5);
      SetColor(2);
      Circle(3*50-7,3*50-6,5);
    end;
 end;

if S=2 then
 begin
  For a:=rY*50 to Y*50 do
    begin
      SetColor(15);
      Circle(X*50-7,a-6,5);
      Delay(Dy);
      SetColor(0);
      Circle(X*50-7,a-6,5);
      SetColor(2);
      Circle(3*50-7,3*50-6,5);
    end;
 end;

if S=4 then
 begin
  For a:=rY*50 downto Y*50 do
    begin
      SetColor(15);
      Circle(X*50-7,a-6,5);
      Delay(Dy);
      SetColor(0);
      Circle(X*50-7,a-6,5);
      SetColor(2);
      Circle(3*50-7,3*50-6,5);
    end;
 end;
if (X=3) and (Y=3) then Inc(Dy,10);
if (X=1) and (Y=5) and (S=4) then goto 2;
rX:=X; rY:=Y;
until keypressed;
2:CloseGraph;
end.