CSS3实现的图片放大镜特效

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

.gallery 
{ 
list-style: none; 
} 
.gallery:before, .gallery__item:last-child 
{ 
position: fixed; 
top: 50%; 
left: 50%; 
margin: -31.25em; 
width: 62.5em; 
height: 62.5em; 
} 
.gallery:before 
{ 
z-index: -1; 
border-radius: 50%; 
content: ''; 
box-shadow: inset 0 0 5em dimgrey, 0 0 0 50vw dimgrey; 
} 
.gallery__item 
{ 
background-blend-mode: luminosity; 
transition: -webkit-transform 0.5s cubic-bezier(0.175, 0.885, 0.32, 1.275), background-image 0.5s; 
} 
.gallery__item:not(:last-child) 
{ 
position: absolute; 
top: 50%; 
left: 50%; 
width: 32vmin; 
height: 32vmin; 
border-radius: 50%; 
box-shadow: 0 0 .5em white; 
} 
.gallery__item:nth-child(1) 
{ 
margin: 13.87457vmin -4.53223vmin; 
-webkit-transform: scale(0.5); 
background: url("imgs/1.jpg") 50% 50% fixed whitesmoke; 
} 
.gallery__item:nth-child(1):hover 
{ 
-webkit-transform: scale(1); 
background-blend-mode: normal; 
cursor: pointer; 
} 
.gallery__item:nth-child(1):hover ~ :last-child 
{ 
background: url("imgs/1.jpg") 50% 50% fixed dimgray; 
} 
.gallery__item:nth-child(1):hover ~ :last-child:after 
{ 
opacity: .001; 
} 
.gallery__item:nth-child(2) 
{ 
margin: 4.13825vmin -40.86867vmin; 
-webkit-transform: scale(0.5); 
background: url("imgs/2.jpg") 50% 50% fixed whitesmoke; 
} 
.gallery__item:nth-child(2):hover 
{ 
-webkit-transform: scale(1); 
background-blend-mode: normal; 
cursor: pointer; 
} 
.gallery__item:nth-child(2):hover ~ :last-child 
{ 
background: url("imgs/2.jpg") 50% 50% fixed dimgray; 
} 
.gallery__item:nth-child(2):hover ~ :last-child:after 
{ 
opacity: .001; 
} 
.gallery__item:nth-child(3) 
{ 
margin: -33.42845vmin -42.83746vmin; 
-webkit-transform: scale(0.5); 
background: url("imgs/3.jpg") 50% 50% fixed whitesmoke; 
} 
.gallery__item:nth-child(3):hover 
{ 
-webkit-transform: scale(1); 
background-blend-mode: normal; 
cursor: pointer; 
} 
.gallery__item:nth-child(3):hover ~ :last-child 
{ 
background: url("imgs/3.jpg") 50% 50% fixed dimgray; 
} 
.gallery__item:nth-child(3):hover ~ :last-child:after 
{ 
opacity: .001; 
} 
.gallery__item:nth-child(4) 
{ 
margin: -46.90963vmin -7.71779vmin; 
-webkit-transform: scale(0.5); 
background: url("imgs/4.jpg") 50% 50% fixed whitesmoke; 
} 
.gallery__item:nth-child(4):hover 
{ 
-webkit-transform: scale(1); 
background-blend-mode: normal; 
cursor: pointer; 
} 
.gallery__item:nth-child(4):hover ~ :last-child 
{ 
background: url("imgs/4.jpg") 50% 50% fixed dimgray; 
} 
.gallery__item:nth-child(4):hover ~ :last-child:after 
{ 
opacity: .001; 
} 
.gallery__item:nth-child(5) 
{ 
margin: -17.67475vmin 15.95615vmin; 
-webkit-transform: scale(0.5); 
background: url("imgs/5.jpg") 50% 50% fixed whitesmoke; 
} 
.gallery__item:nth-child(5):hover 
{ 
-webkit-transform: scale(1); 
background-blend-mode: normal; 
cursor: pointer; 
} 
.gallery__item:nth-child(5):hover ~ :last-child 
{ 
background: url("imgs/5.jpg") 50% 50% fixed dimgray; 
} 
.gallery__item:nth-child(5):hover ~ :last-child:after 
{ 
opacity: .001; 
} 
.gallery__item:last-child 
{ 
z-index: -2; 
} 
.gallery__item:last-child:after 
{ 
position: absolute; 
top: 0; 
right: 0; 
bottom: 0; 
left: 0; 
opacity: .999; 
background: dimgrey; 
transition: opacity 2s; 
content: ''; 
}