.overlay-demo {
  width: 300px;
  height: 100px;
  padding: 10px;
  border: 1px solid #eee;
  background: #FFFFFF;
  box-shadow: 2px 2px 20px rgba(0,0,0,0.15);
}
.next-btn:not(last-child) {
  margin-right: 20px;
}