open System.Windows.Forms
open System.Drawing

type MyForm() as this =
    inherit Form()
    do
        this.SetStyle(ControlStyles.DoubleBuffer, true)
        this.SetStyle(ControlStyles.UserPaint, true)
        this.SetStyle(ControlStyles.AllPaintingInWmPaint, true)

let f = new MyForm(Text="Porygon", TopMost=true)
f.Show()

let mutable n = 3.

let disegnaPoli (g:Graphics) n =
    let gradi = 360. / n
    let rad = (gradi / 180.) * System.Math.PI
    let arr: Point[] = Array.zeroCreate (int(n))
    for i=0 to (int(n-1.)) do
        let k = float(i)
        let x = int(200. * cos(rad * k))
        let y = int(200. * sin(rad * k))
        arr.[i] <- Point(x, y)
//        g.RotateTransform(float32(gradi))
//        arr.[i] <- new Point(200, 0)
//        g.DrawLine(Pens.Black, 0, 0, 200, 0)
    g.FillPolygon(Brushes.DarkCyan, arr)
    //g.Restore(s)

f.Paint.Add( fun e ->
    let g = e.Graphics
    g.SmoothingMode <- Drawing2D.SmoothingMode.HighQuality
    g.TranslateTransform(350.f, 350.f)
    g.RotateTransform(-90.f)
 //   let s = g.Save()
    disegnaPoli g n
  //  disegnaPoli g 3. s
//    disegnaPoli g 4.

)

f.Invalidated.Add( fun _ ->
      if (n = 20.)
           then n <- 3.
      else n <- n+1.
)

let timer = new Timer(Interval=250)
timer.Tick.Add(fun _ ->
    f.Invalidate()
)
timer.Start()