' version 01-09-2017
'    compile with: fbc -s console
' or compile with: fbc -s gui
' hit any key to stop

Dim As UInteger d, blocks, blocksize, ps, col, h, w, x, y1, y2

ScreenInfo w, h
' create display size window, 8bit color (palette), no frame
ScreenRes w, h, 8,, 8

For x = 0 To 255        ' create grayscale palette for
    Palette x, x, x, x  ' the window we just opened
Next

h = h \ 4 : y2 = h -1

If w Mod 64 <> 0 Then w -= (w Mod 64)
blocks = 8 : blocksize = w \ 8

For ps = 1 To 4
    For x = 0 To blocks -1
        col = 255 * x \ (blocks -1)              ' from black to white
        If (ps And 1) = 0 Then col = 255 - col   ' from white to black
        Line (x * blocksize, y1) - (((x +1) * blocksize) -1, y2), col, bf
    Next
    y1 += h : y2 += h
    blocks *= 2 : blocksize \= 2
Next

' empty keyboard buffer
While Inkey <> "" : Wend

Sleep
End