@mixin striped-bg($bg-color: #ccc, $darken-amount: 5%, $stripe-color: darken($bg-color, $darken-amount))
  background-color: $bg-color
  @include background-image(linear-gradient(-45deg, $stripe-color 25%, transparent 25%, transparent 50%, $stripe-color 50%, $stripe-color 75%, transparent 75%, transparent))
  background-size: 40px 40px

.warning
  font-family: sans-serif
  font-weight: bold
  color: #333
  text-align: center
  margin: 2em 1em
  padding: 0.5em
  @include text-shadow(rgba(255,255,255,0.9) 0 1px 1px)
  @include striped-bg(#fcc101, 4%)