#nav_arrow {
  display: none; /* Hidden by default */
  position: fixed;
  bottom: 20px; /* Place the button at the bottom of the page */
  left: 30px; /* Place the button 30px from the right */
  z-index: 99; /* Make sure it does not overlap */
  border: none; /* Remove borders */
  outline: none; /* Remove outline */
  background-color: #779ce5; /* Set a background color */
  color: white; /* Text color */
  cursor: pointer; /* Add a mouse pointer on hover */
  padding: 15px; /* Some padding */
  border-radius: 15%; /* Rounded corners */
  font-size: 18px; /* Increase font size */
box-shadow: 0 3px 20px rgba(0,0,0,.25),
inset 0 2px 0 rgba(255,255,255,.6),
0 2px 0 rgba(0,0,0,.1),
inset 0 0 20px rgba(0,0,0,.1);
opacity:100%;
}

#nav_arrow:hover {
  background-color: #555; /* Add a dark-grey background on hover */
}