body {
  margin: 0;
  padding: 0;
}

p {
  font-size: 16px;
  line-height: 140%;
}

.header { text-align: center; }

.sticky-header-wrap {
  position: relative;
  width: 100%;
  max-width: 728px;
  margin: 40px auto 0;
  overflow: hidden;
}

.sticky-header-wrap h2, .sticky-header-wrap p { width: 100%; }

.sticky-header-wrap h2 {
  max-width: 728px;
  margin: 0;
  padding: 10px;
  background: #C0392B;
  line-height: 120%;
  color: #fff;
}

.sticky-helper { margin-top: 0; }

.sticky-header-hidden { visibility: hidden; }

.sticky-header-wrap { position: relative; }

.sticky-helper {
  position: absolute;
  margin-top: 0 !important;
} /* `h2` is probably not necessary in your case */

.is-sticky {
  background: rgba(0, 0, 0, 0.8) !important;
  color: #fff;
  padding: 10px !important;
}