* {
  box-sizing: border-box;
}


.container {
  padding: 100px 30px;
  width: 100%;
  margin: 0 auto;
  max-width: 900px;
}

.image-stack::after {
  content: ' ';
  display: table;
  clear: both;
}

.image-stack__item--top {
    float: left;
    width: 50%;
    margin-right: -100%;
    padding-top: 30%;
    padding-left: 10%;
    position: relative;
    z-index: 1;
}

.image-stack__item--bottom {
    float: right;
    width: 100%;
}

img {
  width: 100%;
}

.collapsible {
  background: black;
  color: white;
  cursor: pointer;
  padding: 0px;
  width: 100%;
  border: none;
  text-align: left;
  outline: none;
  font-size: 15px;
}

.content {
  padding: 0 18px;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.2s ease-out;
}

.triangle {
  border-right: 10px solid; 
  border-bottom: 10px solid;
  height: 30px;
  width: 30px;
  transform: rotate(-45deg);
}

.triangle-small {
  border-right: 5px solid; 
  border-bottom: 5px solid;
  height: 15px;
  width: 15px;
  transform: rotate(-45deg);
}

input {
  display: none;
}

.accordian div {
  font-size: 26px;  
  height:0;
  overflow:hidden;
  opacity:0;
}
input:checked ~ label:before {
  transform: rotate(90deg)
}
input:checked ~ div {
  padding: 10px;
  opacity: 1;
  height: auto;
}

.vertical-center {
  margin: 0;
  position: absolute;
  top: 50%;
  -ms-transform: translateY(-50%);
  transform: translateY(-50%);
}