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: '0d7';
}

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;
}

<div class="cssbox">
  <a id="image1" href="#image1">
    <img class="cssbox_thumb" src="thumbn-1.jpg">
    <span class="cssbox_full">
      <img src="full-1.jpg">
    </span>
  </a>
  <a class="cssbox_close" href="#void"></a>
  <a class="cssbox_next" href="#image2">></a>
</div>

<div class="cssbox">
  <a id="image1" href="#image2">
    <img class="cssbox_thumb" src="thumbn-2.jpg">
    <span class="cssbox_full">
      <img src="full-2.jpg">
    </span>
  </a>
  <a class="cssbox_close" href="#void"></a>
  <a class="cssbox_prev" href="#image1"><</a>
  <a class="cssbox_next" href="#image3">></a>
</div>

<div class="cssbox">
  <a id="image1" href="#image3">
    <img class="cssbox_thumb" src="thumbn-3.jpg">
    <span class="cssbox_full">
      <img src="full-3.jpg">
    </span>
  </a>
  <a class="cssbox_close" href="#void"></a>
  <a class="cssbox_prev" href="#image2"><</a>