main.css

	/*Put your custom CSS here.

	You may find these CSS3 properties useful:;
		transition
		-webkit-transform
		-webkit-transform-style
		-webkit-backface-visibility
*/
.front {
	position: absolute; /*position doesn't change?*/
	transition:1s; /*when you stop hovering, you want a smooth transition back*/
}
.back {
	position: relative; /*relative positioning needs specification, so here it is at 0, so it will go on top on front*/
	-webkit-transform:rotateY(-180deg); /*start with the backface showing*/
	-webkit-backface-visibility:hidden; /*backface is hidden*/
	transition:1s;
}
.portfolio-item:hover .front{
	transition:1s; 
	-webkit-transform:rotateY(180deg);
}
.portfolio-item:hover .back{
	transition:1s;
	-webkit-transform:rotateY(0deg);
}