Xem mã nguồn của MediaWiki:Common.css

/* Mã CSS đặt ở đây sẽ áp dụng cho mọi giao diện */

#myBtn {
  display: none; /* Hidden by default */
  position: fixed; /* Fixed/sticky position */
  bottom: 20px; /* Place the button at the bottom of the page */
  right: 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: red; /* Set a background color */
  color: white; /* Text color */
  cursor: pointer; /* Add a mouse pointer on hover */
  padding: 15px; /* Some padding */
  border-radius: 10px; /* Rounded corners */
  font-size: 18px; /* Increase font size */
}

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

@import url('https://fonts.googleapis.com/css2?family=Nunito&display=swap');

/* Changes the default font used for MediaWiki to Nunito (does not include headings or monospaced text): */
body {
  font-family: 'Nunito', sans-serif;
}

/* Changes the default font used for MediaWiki headings to Nunito: */
#content h1, 
#content h2 {
  font-family: 'Nunito', sans-serif;
}