Result

折りたたまれた紙をパタパタと広げるようなエフェクト
少し長いコードになりますが、再利用できるので一度書けば同じHTMLで実装可能です。

css

.gallery {
  perspective: 700px;
  width: 50vw;
  display: flex;
  justify-content: center;
  align-items: center;
  flex-flow: row wrap;
}

ul {
  position: relative;
  width: 100px;
  height: 100px;
  margin: 0.1em;
  perspective-origin: center center;
  transform-style: preserve-3d;
  transform: rotateX(40deg);
  transition: all 0.4s;
}

ul:hover {
  transform: translateZ(100px) rotateX(20deg);
  z-index: 999;
}

ul:hover li {
  filter: grayscale(0);
}

li {
  position: absolute;
  left: 0;
  top: 0;
  backface-visibility: hidden;
  width: 100%;
  height: 100%;
  transition: transform 0.3s, filter 1s;
  background: coral;
  filter: grayscale(0.9);
}

li:first-of-type {
  transform: none;
}
li:nth-of-type(2) {
  left: 100%;
  transform-origin: left center;
  transform: rotateY(180deg);
}
li:nth-of-type(3) {
  top: 100%;
  transform-origin: center top;
  transform: rotateX(-180deg);
}
li:nth-of-type(4) {
  left: -100%;
  transform-origin: right center;
  transform: rotateY(-180deg);
}
li:nth-of-type(5) {
  top: -100%;
  transform-origin: center bottom;
  transform: rotateX(180deg);
}
li:nth-of-type(6) {
  top: 100%;
  left: 100%;
  transform-origin: center top;
  transform: rotateX(-180deg);
}
li:nth-of-type(7) {
  top: 100%;
  left: -100%;
  transform-origin: right center;
  transform: rotateY(-180deg);
}
li:nth-of-type(8) {
  top: -100%;
  left: -100%;
  transform-origin: center bottom;
  transform: rotateX(180deg);
}
li:nth-of-type(9) {
  top: -100%;
  left: 100%;
  transform-origin: left center;
  transform: rotateY(180deg);
}
/*
Setup transition-delay, for mouseout state 
*/
li:nth-of-type(2),
li:nth-of-type(3),
li:nth-of-type(4),
li:nth-of-type(5) {
  transition-delay: 0.03s;
}
li:nth-of-type(6),
li:nth-of-type(7),
li:nth-of-type(8),
li:nth-of-type(9) {
  transition-delay: 0s;
}
ul:hover :nth-of-type(2),
ul:hover :nth-of-type(3),
ul:hover :nth-of-type(4),
ul:hover :nth-of-type(5) {
  transition-delay: 0s;
}
ul:hover :nth-of-type(6),
ul:hover :nth-of-type(7),
ul:hover :nth-of-type(8),
ul:hover :nth-of-type(9) {
  transition-delay: 0.2s;
}
/*
Setup planes final state
*/
ul:hover :nth-of-type(2),
ul:hover :nth-of-type(4),
ul:hover :nth-of-type(7),
ul:hover :nth-of-type(9) {
  transform: rotateY(0);
}
ul:hover :nth-of-type(3),
ul:hover :nth-of-type(5),
ul:hover :nth-of-type(6),
ul:hover :nth-of-type(8) {
  transform: rotateX(0);
}
/* 
Set background position
*/
ul li {
  background-size: 300% 300%;
}
li:nth-of-type(1) {
  background-position: center center;
}
li:nth-of-type(2) {
  background-position: right center;
}
li:nth-of-type(3) {
  background-position: center bottom;
}
li:nth-of-type(4) {
  background-position: left center;
}
li:nth-of-type(5) {
  background-position: center top;
}
li:nth-of-type(6) {
  background-position: right bottom;
}
li:nth-of-type(7) {
  background-position: left bottom;
}
li:nth-of-type(8) {
  background-position: left top;
}
li:nth-of-type(9) {
  background-position: right top;
}
/*
Set background image source
*/
ul:nth-of-type(1) li {
  background-image: url(//picsum.photos/1200/800?image=1011);
}
ul:nth-of-type(1) {
  width: 120px;
  height: 80px;
}

li {
  text-indent: 999px;
  overflow: hidden;
}

html

<div class="gallery">
  <ul>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
  </ul>
</div>

via

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