const N=20;
type TRect=record
x,y,x1,x2,y1,y2:integer;
Color:TColor;
end;

var Mas:array[1..N] of TRect;

procedure DrawRect(Rec:TRect);
begin
Form1.PaintBox1.Canvas.Pen.color:=Rec.Color;
Form1.PaintBox1.Canvas.Brush.Color:=Rec.Color;
Form1.PaintBox1.Canvas.Rectangle(Rec.x1,Rec.x2,Rec.y1,Rec.y2);
end;

procedure HideRect (Rec:TRect);
begin
Form1.PaintBox1.Canvas.Pen.Color:=Form1.PaintBox1.Color;
Form1.PaintBox1.Canvas.Brush.Color:=Form1.PaintBox1.Color;
Form1.PaintBox1.Canvas.Rectangle(Rec.x1,Rec.x2,Rec.y1,Rec.y2);
end;

function GenerateRect(N:integer):TRect;
var
Rec:TRect;
begin
Rec.x1:=Random(200)+1;
Rec.x2:=Random(200)+1;
Rec.y1:=Random(200)+1;
Rec.y2:=Random(200)+1;
Rec.x:=Random(Form1.PaintBox1.Width div 2)-1;
Rec.y:=Random(Form1.PaintBox1.Height div 2)-1;
Rec.Color:=RGB(Random(256),Random(256),Random(256));
Result:=Rec
end;

procedure TForm1.PaintBox1Paint(Sender: TObject);
var i,x,y,w,h:integer;
begin
w:=PaintBox1.Width;
h:=PaintBox1.Height;
x:=w div 2;
y:=h div 2;
PaintBox1.Canvas.Rectangle(0,0,w,h);
PaintBox1.Canvas.MoveTo(x,0);
PaintBox1.Canvas.LineTo(y,h);
PaintBox1.Canvas.MoveTo(0,y);
PaintBox1.Canvas.LineTo(w,x);
for i:=1 to N do
DrawRect(Mas[i]);
HideRect(Mas[i]);
end;

procedure TForm1.FormCreate(Sender: TObject);
var i:integer;
begin
for i:=1 to N do
Mas[i]:=GenerateRect(i);
end;

procedure TForm1.Timer1Timer(Sender: TObject);
var k:integer;
begin
k:=random(n)+1;
HideRect(Mas[k]);
Mas[k]:=GenerateRect(N);
DrawRect(Mas[k]);
end;
end.