.container {
  width: 680px;
  height: 2000px;
  margin: 30px auto;
  font-size: 24px;
}

.subcontainer {
  width: 100%;
  position: relative;
}

.fixed-parent {
  /* Try changing the position of this element to absolute. It will trigger some JS which emulates the behaviour of "position: fixed" without the stacking context. */
  position: fixed;
  width: 600px;
  height: 400px;
  background-color: #eee;
  padding: 20px 40px;
}

p {
  margin: 0 0 20px;
}

.fixed-child {
  display: inline-block;
  vertical-align: top;
  position: relative;
  width: 200px;
  height: 200px;
  padding: 20px;
  background-color: pink;
  z-index: 3;
}

.other-fixed-child {
  display: inline-block;
  vertical-align: top;
  margin-left: 110px;
  position: relative;
  width: 200px;
  height: 200px;
  padding: 20px;
  background-color: lightblue;
  z-index: 1;
}

.random-zindex {
  position: absolute;
  top: 400px;
  left: 200px;
  z-index: 2;
  width: 260px;
  height: 260px;
  padding: 20px;
  background-color: palegreen;
}

.just-sitting-here {
  position: absolute;
  top: 780px;
  left: 300px;
  width: 180px;
  height: 180px;
  padding: 10px;
  background-color: #fafbac;
}