body{
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
}

html{
  background: linear-gradient(rgba(4,9,30,0.2),rgba(4,9,30,0.2)),url('Hoorns_Haven.jpg') no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
  /* Source: https://css-tricks.com/perfect-full-page-background-image/ */
}

a{
  color: #fff;
}

.header{
  background: rgba(0,0,0,0.3);
  box-shadow: 1px 1px 4px 0 rgba(0,0,0,.1);
  position: fixed;
  width: 100%;
  z-index: 3;
}

.header ul{
  margin: 0;
  padding: 0;
  list-style: none;
  overflow: hidden;
  background: rgba(0,0,0,0);
}

.header ul a{
  display: block;
  padding: 20px;
  border-right: 1px solid #aaa;
  text-decoration: none;
}

.header ul a:hover{
  background-color: #ddd;
  background: rgba(0,0,0,0.5);
}

.header .logo{
  float: left;
  display: block;
  font-size: 2em;
  padding: 10px 20px;
  text-decoration: none;
}

.header .menu{
  clear: both;
  max-height: 0;
  transition: max-height .2s ease-out;
}

.header .menu-icon{
  padding: 28px 20px;
  position: relative;
  float: right;
  cursor: pointer;
}

.header .menu-icon .nav-icon{
  background: #fff;
  display: block;
  height: 2px;
  width: 18px;
  position: relative;
  transition: background .2s ease-out;
}

.header .menu-icon .nav-icon:before{
  background: #fff;
  content: "";
  display: block;
  height: 100%;
  position: absolute;
  width: 100%;
  position: absolute;
  transition: all .2s ease-out;
  top: 5px;
}

.header .menu-icon .nav-icon:after{
  background: #fff;
  content: "";
  display: block;
  height: 100%;
  position: absolute;
  width: 100%;
  position: absolute;
  transition: all .2s ease-out;
  top: -5px;
}

.header .menu-btn{
  display: none;
}

.header .menu-btn:checked ~ .menu{
  max-height: 240px;
}

.header .menu-btn:checked ~ .menu-icon .nav-icon{
 background: transparent;
}

.header .menu-btn:checked ~ .menu-icon .nav-icon:before{
  transform: rotate(-45deg);
  top: 0;
}

.header .menu-btn:checked ~ .menu-icon .nav-icon:after{
  transform: rotate(45deg);
  top: 0;
}

@media (min-width: 42em){

  .header li{
    float: left;
  }
  .header li a{
    padding: 20px 30px;
  }
  .header .menu{
    clear: none;
    float: right;
    max-height: none;
  }
  .header .menu-icon{
    display: none;
  }

}