Playing with Bézier curve

using System;
using System.Drawing;
using System.Windows.Forms;

namespace DoTheBezier
{
    public partial class Form1 : Form
    {
        const int ptSize = 10;
        bool wipeTheBoard = true;
        Point MouseDownLocation;
        Bitmap[] bmap = new Bitmap[4];

        public Form1()
        {
            InitializeComponent();
            for (int i = 0; i < 4; i++)
			{
                bmap[i] = new Bitmap(ptSize, ptSize);
			}
            pctB_StartPt.MouseDown += pict_MouseDown; pctB_StartPt.MouseMove += pict_MouseMove;
            pctB_CtrlPt1.MouseDown += pict_MouseDown; pctB_CtrlPt1.MouseMove += pict_MouseMove;
            pctB_CtrlPt2.MouseDown += pict_MouseDown; pctB_CtrlPt2.MouseMove += pict_MouseMove;
            pctB_EndPt.MouseDown += pict_MouseDown; pctB_EndPt.MouseMove += pict_MouseMove;
        }

        private void pict_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                MouseDownLocation = e.Location;
            }
        }

        private void pict_MouseMove(object sender, MouseEventArgs e)
        {
            PictureBox P = sender as PictureBox;           
            if (e.Button == MouseButtons.Left)
            {
                P.Left = e.X + P.Left - MouseDownLocation.X;
                P.Top = e.Y + P.Top - MouseDownLocation.Y;
                pnlBoard.Refresh();
            }
        }

        private void btnClear_Click(object sender, EventArgs e)
        {              
            wipeTheBoard = true;
            pnlBoard.Refresh();
        }

        private void btnShow_Click(object sender, EventArgs e)
        {
            wipeTheBoard = false;
            pnlBoard.Refresh();
        }

        private void MakePoint(PictureBox PB, Bitmap bmap, Brush B)
        {
            Graphics GR;
            Rectangle rect = new Rectangle(0, 0, ptSize, ptSize);
            GR = Graphics.FromImage(bmap); //static method
            GR.FillEllipse(B, rect);
            PB.Image = bmap;
        }

        private void pnlBoard_Paint(object sender, PaintEventArgs e)
        {
            Graphics G = e.Graphics;
            if (!wipeTheBoard)
            {
                MakePoint(pctB_StartPt, bmap[0], Brushes.Blue);
                MakePoint(pctB_CtrlPt1, bmap[1], Brushes.Red);
                MakePoint(pctB_CtrlPt2, bmap[2], Brushes.Green);
                MakePoint(pctB_EndPt, bmap[3], Brushes.Yellow);
                
                G.DrawBezier(new Pen(Color.Blue, 2f), 
                    pctB_StartPt.Location, 
                    pctB_CtrlPt1.Location, 
                    pctB_CtrlPt2.Location,
                    pctB_EndPt.Location);
            }
            else
            {
                G.Clear(pnlBoard.BackColor);
                pctB_StartPt.Image = null; 
                pctB_CtrlPt1.Image = null; 
                pctB_CtrlPt2.Image = null;
                pctB_EndPt.Image = null; 
                wipeTheBoard = false;
            }
        }

        private void pnlBoard_MouseMove(object sender, MouseEventArgs e)
        {
            lblX.Text = "X: " + e.X.ToString();
            lblY.Text = "Y: " + e.Y.ToString();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //reset the movable picts to the BackColor of the panel
            //in designemode they have a black color, to be visible.
            pctB_StartPt.BackColor = Color.FromArgb(0, 230, 230);
            pctB_CtrlPt1.BackColor = Color.FromArgb(0, 230, 230);
            pctB_CtrlPt2.BackColor = Color.FromArgb(0, 230, 230);
            pctB_EndPt.BackColor = Color.FromArgb(0, 230, 230);
        }
    }
}