new_contents: 
  
  
  def circles(x, y,cnt, dist):
      for i in range(cnt):
          r = i * dist
          circle(x, y, r)
  
  
  var("c2x", NUMBER, 300, 0, 600)
  var("d", NUMBER, 1.0, 0.1, 5.0)
  
  nofill()
  strokewidth( d )
  stroke(0,0,0, 1)
  
  circles(200,250, 40, 5)
  circles(c2x,250, 40, 5)
  
  
subject: Create interference.py