public partial class Form1 : Form
{
	private bool isMouseDown;
	Bitmap canvas;

	public Form1()
	{
		InitializeComponent();
	}

	private void Form1_Load(object sender, EventArgs e)
	{
		this.Size = new Size(500, 500);
		this.MouseDown += new MouseEventHandler(Form1_MouseDown);
		this.MouseUp += new MouseEventHandler(Form1_MouseUp);
		this.MouseMove += new MouseEventHandler(Form1_MouseMove);

		canvas = new Bitmap(this.Size.Width, this.Size.Height);
	}

	private void Form1_MouseDown(object sender, MouseEventArgs e)
	{
		isMouseDown = true;
	}

	private void Form1_MouseUp(object sender, MouseEventArgs e)
	{
		isMouseDown = false;
	}

	private void Form1_MouseMove(object sender, MouseEventArgs e)
	{
		if (isMouseDown)
		{
			Color c = Color.Black;
			Random r = new Random();
			int x = e.X, y = e.Y, s = r.Next(10);

			for (int i = 0; i < s; i++)
			{
				try
				{
					switch (r.Next(8))
					{
						case 0:
							canvas.SetPixel(x + s, y, c);
							break;
						case 1:
							canvas.SetPixel(x - s, y, c);
							break;
						case 2:
							canvas.SetPixel(x, y + s, c);
							break;
						case 3:
							canvas.SetPixel(x, y + -s, c);
							break;
						case 4:
							canvas.SetPixel(x + s, y + s, c);
							break;
						case 5:
							canvas.SetPixel(x - s, y + s, c);
							break;
						case 6:
							canvas.SetPixel(x - s, y - s, c);
							break;
						case 7:
							canvas.SetPixel(x - s, y - s, c);
							break;
					}
				}
				catch { }
			}

			canvas.SetPixel(e.X, e.Y, Color.Black);

			using (Graphics g = this.CreateGraphics())
			{
				g.DrawImage(canvas, Point.Empty);
			}
		}
	}