Как нарисовать прямоугольник, изменить его координаты и нарисовать заново уже без первого прямоугольника?

{ Пример программы для процедуры InitGraph }
Uses Graph, Crt;
 
var
  grDriver: Integer;
  grMode: Integer;
  ErrCode: Integer;
  x, y, i: integer;
 
begin
  grDriver := Detect;
  InitGraph(grDriver, grMode, '');
  ErrCode := GraphResult;
  if ErrCode = grOk Then
  begin
    { Графика }
    x := 100;y := 100;
    SetLineStyle(SolidLn, 0, ThickWidth);
    SetWriteMode(XorPut);
    for i := 1 to 100 do
    begin
      Rectangle(x, y, x + 10, y + 10);
      delay(100);
      Rectangle(x, y, x + 10, y + 10);
      inc(x, 5);inc(y, 5);
    end;
    ReadLn;
    CloseGraph;
  end
  Else
    WriteLn('Ошибка инициализации графики:', GraphErrorMsg(ErrCode));
end.

SetWriteMode(XorPut);

SetWriteMode(XorPut);

program MovingFlag;
 
uses graph, wincrt, math;
 
const Left = chr(97);
      Right = chr(100);
      Stop = ' ';
      
var x1, y1, x2, y2, x3, y3, x4, y4: real;
    rad: real;
    key: char;
    i: integer;
    
procedure initializeGraph;
var gd, gm: integer;
begin
    gd:=detect;
    initGraph(gd, gm, '');
    if graphresult<0 then
    begin
        writeln('Error.');
        halt;
    end;
end;
 
procedure drawFlag(x2:real; y2:real; x3:real; y3:real; x4:real; y4:real);
begin
    moveto(round(x1), round(y1));
    lineto(round(x2), round(y2));
    lineto(round(x3), round(y3));
    lineto(round(x4), round(y4));
end;
 
begin
    initializeGraph;
    setwritemode(XORPut);
    
    x1:=getmaxx div 2;
    y1:=getmaxy div 2;
    x2:=getmaxx div 2;
    y2:=y1 - 200;
    x3:=x2 + 50;
    y3:=y2 + 25;
    x4:=getmaxx div 2;
    y4:=y3 + 25;
    
    drawFlag(x2, y2, x3, y3, x4, y4);
    
    repeat
        if keypressed then
        begin
            key:=readkey;
            case key of
                Left:
                begin
                    inc(i);
                    rad:=((1*PI)/180)*(-1);
                    x2:=x2*(cos(rad))-y2*(sin(rad))+(x1*(1-cos(rad)))+y1*(sin(rad));
                    y2:=y2*(cos(rad))+x2*(sin(rad))+(y1*(1-cos(rad)))-x1*(sin(rad));
                    x3:=x3*(cos(rad))-y3*(sin(rad))+(x1*(1-cos(rad)))+y1*(sin(rad));
                    y3:=y3*(cos(rad))+x3*(sin(rad))+(y1*(1-cos(rad)))-x1*(sin(rad));
                    x4:=x4*(cos(rad))-y4*(sin(rad))+(x1*(1-cos(rad)))+y1*(sin(rad));
                    y4:=y4*(cos(rad))+x4*(sin(rad))+(y1*(1-cos(rad)))-x1*(sin(rad));
                    drawFlag(x2, y2, x3, y3, x4, y4);
                end;
                Right:
                begin
                    inc(i);
                    rad:=(1*PI)/180;
                    x2:=x2*(cos(rad))-y2*(sin(rad))+(x1*(1-cos(rad)))+y1*(sin(rad));
                    y2:=y2*(cos(rad))+x2*(sin(rad))+(y1*(1-cos(rad)))-x1*(sin(rad));
                    x3:=x3*(cos(rad))-y3*(sin(rad))+(x1*(1-cos(rad)))+y1*(sin(rad));
                    y3:=y3*(cos(rad))+x3*(sin(rad))+(y1*(1-cos(rad)))-x1*(sin(rad));
                    x4:=x4*(cos(rad))-y4*(sin(rad))+(x1*(1-cos(rad)))+y1*(sin(rad));
                    y4:=y4*(cos(rad))+x4*(sin(rad))+(y1*(1-cos(rad)))-x1*(sin(rad));
                    drawFlag(x2, y2, x3, y3, x4, y4);
                    delay(100);
                    drawFlag(x2, y2, x3, y3, x4, y4);
                end;
                Stop:
                begin
                    delay(3000);
                    halt;
                end;
            end;
        end;
    until (1=0);
end.