#define ORDER 64

_window = 1

void local fn BuildWindow
  CGRect r = fn CGRectMake( 0, 0, 651, 661 )
  window _window, @"Order 64 Hilbert Curve In FutureBasic", r, NSWindowStyleMaskTitled
  WindowSetBackgroundColor( _window, fn ColorBlack )
end fn

void local fn HilbertCurve( x as long, y as long, lg as long, i1 as long, i2 as long )
  if ( lg == 1 )
    line to ( ORDER-x ) * 10, ( ORDER-y ) * 10
    exit fn
  end if
  lg = lg / 2
  fn HilbertCurve( x+i1*lg,     y+i1*lg,     lg, i1, 1-i2 )
  pen 2.0
  fn HilbertCurve( x+i2*lg,     y+(1-i2)*lg, lg, i1,   i2 )
  fn HilbertCurve( x+(1-i1)*lg, y+(1-i1)*lg, lg, i1,   i2 )
  fn HilbertCurve( x+(1-i2)*lg, y+i2*lg,     lg, 1-i1, i2 )
end fn

fn BuildWindow
pen -2.0, fn ColorGreen
fn HilbertCurve( 0, 0, ORDER, 0, 0 )

HandleEvents