parallax = ->
  if $('#js-parallax-window').length > 0
    plxBackground = $('#js-parallax-background')
    plxWindow = $('#js-parallax-window')
    plxWindowTopToPageTop = $(plxWindow).offset().top
    windowTopToPageTop = $(window).scrollTop()
    plxWindowTopToWindowTop = plxWindowTopToPageTop - windowTopToPageTop
    plxBackgroundTopToPageTop = $(plxBackground).offset().top
    windowInnerHeight = window.innerHeight
    plxBackgroundTopToWindowTop = plxBackgroundTopToPageTop - windowTopToPageTop
    plxBackgroundTopToWindowBottom = windowInnerHeight - plxBackgroundTopToWindowTop
    plxSpeed = 0.35
    plxBackground.css 'top', -(plxWindowTopToWindowTop * plxSpeed) + 'px'
  return

$(document).ready ->
  if $('#js-parallax-window').length
    parallax()
  return
$(window).scroll (e) ->
  if $('#js-parallax-window').length
    parallax()
  return