gistfile1.coffee

content = @elements.oContent
nowAtTop = (content.scrollTop() is 0)
nowAtBottom = (content.scrollTop() >= content.children('ul').height() - content.height())
if nowAtTop is @atTop and nowAtBottom is @atBottom
  return
@atTop = nowAtTop
@atBottom = nowAtBottom

shadowSize = '30px'
shadowColor = '#000'
shadow = 'none'
if not nowAtTop and not nowAtBottom
  shadow = "inset 0  #{shadowSize} #{shadowSize} -#{shadowSize} #{shadowColor}, inset 0 -#{shadowSize} #{shadowSize} -#{shadowSize} #{shadowColor}"
else if nowAtBottom
  shadow = "inset 0  #{shadowSize} #{shadowSize} -#{shadowSize} #{shadowColor}"
else if nowAtTop
  shadow = "inset 0 -#{shadowSize} #{shadowSize} -#{shadowSize} #{shadowColor}"

content.css
  '-webkit-box-shadow': shadow
  '-moz-box-shadow': shadow
  'box-shadow': shadow