var onoff : int := 0
var oldmx, oldmy : int



    if mb = 1 and current_tool = "pen" and onoff = 0 then
        onoff := 1
        drawdot (mx, my, col)
        oldmx := mx
        oldmy := my
    elsif mb = 1 and current_tool = "pen" and onoff = 1 then
        drawline (oldmx, oldmy, mx, my, col)
        oldmx := mx
        oldmy := my
        drawdot (mx, my, col)
    elsif mb = 0 and current_tool = "pen" and onoff = 1 then
        onoff := 0
    end if