Почему графика тормозит компьютер

using System;
using System.Drawing;
using System.Windows.Forms;
using System.ComponentModel;
 
class Program
{
    [STAThread]
    public static void Main()
    {
      Application.EnableVisualStyles();
      Application.SetCompatibleTextRenderingDefault(false);
      Application.Run(new Form1());
    }
 
  public class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }
 
    private void Form1_Load(object sender, EventArgs e)
    {
      this.BackColor = System.Drawing.Color.Blue;
      this.ForeColor = System.Drawing.Color.Red;
      this.ResizeRedraw = true;
    }
 
    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
      BackgroundWorker bw = (BackgroundWorker)sender;
      DrawObj objOnDrawing;
      for (int k = 1; k < 6; k++)
      {
        for (int x = -50; x < 51; x++)
        {
          objOnDrawing = new DrawObj()
          {
            Color = Color.Magenta,
            Rectangle = new Rectangle(x * k + 195, 225, 10, -80)
          };
          if (bw.CancellationPending) break;
          bw.ReportProgress(0, objOnDrawing);
          System.Threading.Thread.Sleep(10);
          objOnDrawing.Color = Color.Orange;
          if (bw.CancellationPending) break;
          bw.ReportProgress(0, objOnDrawing);
        }
        if (bw.CancellationPending) break;
      }
    }
 
    public class DrawObj
    {
      public System.Drawing.Color Color { get; set; }
      public System.Drawing.Rectangle Rectangle { get; set; }
 
      public DrawObj()
      { }
    }
 
    private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
      DrawObj curObj = (DrawObj)e.UserState;
      Graphics g = this.CreateGraphics();
      g.DrawEllipse(new Pen(curObj.Color, 3), curObj.Rectangle);
    }
 
    private void Form1_Move(object sender, EventArgs e)
    {
      if (!backgroundWorker1.IsBusy)
      {
        Graphics g = this.CreateGraphics();
        g.Clear(this.BackColor);
        backgroundWorker1.RunWorkerAsync();
      }
    }
 
    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
      if (backgroundWorker1.IsBusy)
      {
        backgroundWorker1.CancelAsync();
        e.Cancel = true;
        formIsClosing = true;
      }
    }
 
    private bool formIsClosing = false;
 
    private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
      if (formIsClosing) this.Close();
    }
 
    private System.ComponentModel.IContainer components = null;
 
    protected override void Dispose(bool disposing)
    {
      if (disposing && (components != null))
      {
        components.Dispose();
      }
      base.Dispose(disposing);
    }
 
    private void InitializeComponent()
    {
      this.backgroundWorker1 = new System.ComponentModel.BackgroundWorker();
      this.SuspendLayout();
      // 
      // backgroundWorker1
      // 
      this.backgroundWorker1.WorkerReportsProgress = true;
      this.backgroundWorker1.WorkerSupportsCancellation = true;
      this.backgroundWorker1.DoWork += new System.ComponentModel.DoWorkEventHandler(this.backgroundWorker1_DoWork);
      this.backgroundWorker1.ProgressChanged += new System.ComponentModel.ProgressChangedEventHandler(this.backgroundWorker1_ProgressChanged);
      this.backgroundWorker1.RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.backgroundWorker1_RunWorkerCompleted);
      // 
      // Form1
      // 
      this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
      this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
      this.ClientSize = new System.Drawing.Size(584, 322);
      this.Name = "Form1";
      this.Text = "Form1";
      this.FormClosing += new System.Windows.Forms.FormClosingEventHandler(this.Form1_FormClosing);
      this.Load += new System.EventHandler(this.Form1_Load);
      this.Move += new System.EventHandler(this.Form1_Move);
      this.ResumeLayout(false);
    }
 
    private System.ComponentModel.BackgroundWorker backgroundWorker1;
  }
}