Анимация движения шарика по окружности

//---------------------------------------------------------------------------
 
#include <vcl.h>
#pragma hdrstop
#include "nit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
int x, y;
int r;
int dx, dy;
TColor color;
 
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
}
//---------------------------------------------------------------------------
 
void __fastcall TForm1::Timer1Timer(TObject *Sender)
{
x += dx;
if (x+r>ClientWidth || x<r)
dx = -dx;
Invalidate();
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormCreate(TObject *Sender)
{
  randomize();
r = 25;
dx = 5;
x = 260;
y = 160;
 color = clGreen;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormPaint(TObject *Sender)
{
Canvas->Pen->Color = color;
Canvas->Brush->Color = color;
Canvas->Ellipse(x-r,y-r,x+r,y+r);
}
//---------------------------------------------------------------------------