text: # HelloWorld for VPython - HaJo Gurt - 2014-09-20
  from visual import *
  
  scene.title = "VPython Demo"
  scene.background = color.gray(0.2)
  
  scene.width  = 600
  scene.height = 400
  scene.range  = 4
  #scene.autocenter = True
  
  S = sphere(pos=(0,0,0), radius=1, material=materials.earth)
  rot=0.005
  
  txPos=(0, 1.2, 0)
  
  from visual.text import *
  # Old 3D text machinery (pre-Visual 5.3): numbers and uppercase letters only:
  T1 = text(pos=txPos, string='HELLO', color=color.red, depth=0.3, justify='center')
  
  import vis
  # new text object, can render text from any font (default: "sans") :
  T2 = vis.text(pos=txPos, text="Goodbye", color=color.green, depth=-0.3, align='center')
  T2.visible=False
  
  Lbl_w = label(pos=(0,0,0), text='World', color=color.cyan,
                xoffset=80, yoffset=-40)     # in screen-pixels
  
  L1 = label(pos=(0,-1.5,0), text='Drag with right mousebutton to rotate view',   box=0)
  L2 = label(pos=(0,-1.9,0), text='Drag up+down with middle mousebutton to zoom', box=0)
  L3 = label(pos=(0,-2.3,0), text='Left-click to change', color=color.orange,     box=0)
  
  print "Hello World"     # Console
  
  
  cCount = 0
  def change():
      global rot, cCount
      cCount=cCount+1
      print "change:", cCount
      rot=-rot
      if T1.visible:
          T1.visible=False
          T2.visible=True
      else:
          T1.visible=True
          T2.visible=False
  
  scene.bind( 'click', change )
  
  while True:
    rate(100)
    S.rotate( angle=rot, axis=(0,1,0) )
  