CSS
.container {
display: -webkit-flex;
display: -ms-flexbox;
display: flex;
-webkit-justify-content: center;
-ms-flex-pack: center;
justify-content: center;
-webkit-flex-wrap: wrap;
-ms-flex-wrap: wrap;
flex-wrap: wrap;
}
img {
-webkit-filter: grayscale(100%);
filter: grayscale(100%);
cursor: pointer;
transition: box-shadow 0.25s ease-out 0s,
-webkit-filter 0.25s ease-out 0.15s;
transition: box-shadow 0.25s ease-out 0s,
filter 0.25s ease-out 0.15s;
transition: box-shadow 0.25s ease-out 0s,
filter 0.25s ease-out 0.15s,
-webkit-filter 0.25s ease-out 0.15s;
border-radius: 3px;
-webkit-flex: 0 1 auto;
-ms-flex: 0 1 auto;
flex: 0 1 auto;
margin: 0.5em;
}
img:hover {
-webkit-filter: none;
filter: none;
box-shadow: -1px 1px 10px #000;
}