如何在WINFORM中彈出一個又控制元件的對話方塊  能給個簡單的示範C#程式碼嗎

順便問問 這段程式碼是啥意思啊

        private void btn_catchMe_Click(object sender, System.EventArgs e)
        {
            MessageBox.Show("抓到我了，算你聰明！","抓到了");
        }

 private void Form1_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            int border = 50;//??
        int x = e.X;
            int y = e.Y;
            int left = btn_catchMe.Left;//不懂????解釋一下好嗎
      int right = btn_catchMe.Right;
            int top = btn_catchMe.Top;
            int bottom = btn_catchMe.Bottom;
            /* 滑鼠到按鈕附近(20個象素) */             //??????? 下面最好每句解釋下
if( x > left - border && x < right + border && y > top - border && y < bottom + border)
            {
                btn_catchMe.Top += (y > top ? -20 : 20);
                if(btn_catchMe.Top > Form1.ActiveForm.Size.Height || btn_catchMe.Bottom < 0)
                {
                    btn_catchMe.Top = Form1.ActiveForm.Size.Height/2;
                }
                btn_catchMe.Left += (x > left ? -20 : 20);
                if(btn_catchMe.Left > Form1.ActiveForm.Size.Width || btn_catchMe.Right < 0)
                {
                    btn_catchMe.Left = Form1.ActiveForm.Size.Width/2;
                }

            }