' version 14-03-2017
'    compile with: fbc -s console
' or compile with: fbc -s gui

Dim As UInteger ps, col, h, w, x, y1, y2
ScreenInfo w, h

' create display size window, 8bit color (palette), no frame
ScreenRes w, h, 8,, 8
' vga palette black = 0 and white = 15

h = h \ 4 : y2 = h -1

For ps = 1 To 4
    col = 0
    For x = 0 To (w - ps -1) Step ps
        Line (x, y1) - (x + ps -1, y2), col, bf
        col = 15 - col ' col alternate between 0 (black) and 15 (white)
    Next
    y1 += h : y2 += h
Next

' empty keyboard buffer
While InKey <> "" : Wend
'Print : Print "hit any key to end program"
Sleep
End