body {
  background: #fff;
}

section {
  padding: 100px 0;
}

.hero {
  color: #fff;
  background-image: url(//placeimg.com/1500/600/any);
  background-repeat: no-repeat;
  background-size: cover;
  position: relative;
}
.hero:before {
  content: "";
  background: rgba(0, 0, 0, 0.6);
  position: absolute;
  left: 0;
  top: 0;
  right: 0;
  bottom: 0;
}
.hero .container {
  position: relative;
  z-index: 2;
}

.megamenu {
  background: #007bff;
  z-index: 15;
}
.megamenu .megamenu-nav {
  padding: 0;
  margin: 0;
}
.megamenu .megamenu-nav .nav-item {
  display: block;
}
.megamenu .megamenu-nav .nav-item.is-open > .megamenu-content {
  visibility: visible;
  opacity: 1;
}
.megamenu .megamenu-nav .nav-item.is-open > .nav-link {
  background: #fff;
  color: #333;
}
.megamenu .megamenu-nav .nav-link {
  color: #fff;
  padding: 15px 30px;
}
.megamenu .megamenu-nav .nav-link:hover {
  background: #fff;
  color: #333;
}
.megamenu .megamenu-content {
  position: absolute;
  left: 0;
  right: 0;
  top: 54px;
  overflow: hidden;
  visibility: hidden;
  opacity: 0;
  z-index: 14;
  transition: all .3s ease-in-out;
}
.megamenu .megamenu-content .container {
  padding: 45px 15px;
}
.megamenu .megamenu-content .subnav {
  margin: 0;
  padding: 0;
}
.megamenu .megamenu-content .subnav-item {
  display: block;
}
.megamenu .megamenu-content .subnav-item .subnav-link {
  padding: 10px 0;
  display: block;
}

.megamenu-background {
  background: #fff;
  position: absolute;
  left: 0;
  top: 54px;
  right: 0;
  height: 0;
  transition: all .3s ease-in-out;
  box-shadow: 0px 10px 20px rgba(0, 0, 0, 0.15);
  z-index: 13;
}

.megamenu-dim {
  background: rgba(0, 0, 0, 0.6);
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  top: 54px;
  visibility: hidden;
  opacity: 0;
  z-index: -12;
  transition: all .3s ease-in-out;
}
body.megamenu-visible .megamenu-dim {
  z-index: 12;
  visibility: visible;
  opacity: 1;
}