//draws the screen
private void canvas_Paint(object sender, PaintEventArgs e)
{
//checks to see if the background should be drawn
if (!transparentBackground)
{
e.Graphics.FillRectangle(Brushes.White, 0, 0, canvas.Width, canvas.Height);
}
if (background != null)
{
background.Draw(e.Graphics);
}
foreach (Layer l in layers)
{
l.Draw(e);
}
}