CSSBox/cssbox.css

/* The work below, CSSBox, is released under the Creative Commons
   Attribution-ShareAlike 4.0 license and is available on
   https://notabug.org/SylvieLorxu/CSSBox. You are not required to add
   additional credit to your website, just leave the above text in this file */
div.cssbox {
  display: inline-block;
}

span.cssbox_full {
  z-index: 999;
  position: fixed;
  height: 100%;
  width: 100%;
  background-color: rgba(0,0,0,0.8);
  top: 0;
  left: 0;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.5s linear;
}

span.cssbox_full img {
  position: fixed;
  background-color: white;
  margin: 0;
  padding: 0;
  max-height: 90%;
  max-width: 90%;
  top: 50%;
  left: 50%;
  margin-right: -50%;
  transform: translate(-50%, -50%);
  box-shadow: 0 0 20px black;
}

a.cssbox_close,
a.cssbox_prev,
a.cssbox_next {
  z-index: 999;
  position: fixed;
  text-decoration: none;
  visibility: hidden;
  color: white;
  font-size: 36px;
}

a.cssbox_close {
  top: 1%;
  right: 1%
}

a.cssbox_close::after {
  content: '\00d7';
}

a.cssbox_prev,
a.cssbox_next {
  top: 50%;
  transform: translate(0%, -50%);
}

a.cssbox_prev {
  left: 5%;
}

a.cssbox_next {
  right: 5%;
}

a:target ~ a.cssbox_close,
a:target ~ a.cssbox_prev,
a:target ~ a.cssbox_next {
  visibility: visible;
}

a:target > img.cssbox_thumb + span.cssbox_full {
  visibility: visible;
  opacity: 1;
  pointer-events: initial;
}

span.cssbox_full {
  cursor: initial;
}
/* This is the end of CSSBox */