* {box-sizing:border-box}


/* forward & Back buttons */
.Back, .forward {
  cursor: pointer;
  position: absolute;
  top: 10%;
  width: auto;
  margin-top: -23px;
  padding: 10px;
  color: black;
  opacity: 0.5;
  font-weight: bold;
  font-size: 78px;
  transition: 0.9s ease;
  border-radius: 0 5px 5px 0;
  user-select: none;
}

/* Place the "forward button" to the right */
.forward {
  right: 0;
  border-radius: 4px 0 0 4px;
}

/*when the user hovers,add a black background with some little opacity */
.Back:hover, .forward:hover {
  background-color: rgba(0,0,0,0.8);
}