.wrapper {
  position: relative;
  display: block;
  margin: 0 auto;
  top: 100px;
}
.button {
  display: block;
  height: 3rem;
  width: 3rem;
  background: #3AADF4;
  color: white;
  border-radius: 100%;
  text-align: center;
  line-height: 3;
  margin: 20px;
  z-index: 1;
  position: relative;
}
.rectangle {
  width: 7rem;
  height: 3rem;
  background: rgba(162,162,161,1);
  position: absolute;
  top:0;
  left: 2.5rem;
  z-index: 0;
  border-radius: 4px;
}
/* Animatie*/
.button {
  transition: transform 0.5s ease;
}
.rectangle {
  transition: width 0.5s ease;
}
.active .button {
  transform: rotateZ(360deg);
}
.rectangle:not(.active) {
  width: 0;
}