ul.pdf_file{
	display: flex;
	flex-wrap:wrap;
	margin: 0 auto 10%;
}


ul.pdf_file li img{
	-webkit-box-shadow:1px 1px 6px #ccc;
	-moz-box-shadow:1px 1px 6px #ccc;
	box-shadow: 1px 1px 6px #ccc;
	position: relative;
}

.fileinfo{
	margin: .8em 0 0 0
}

ul.pdf_file li figure{
	position: relative;
	display: block
}

ul.pdf_file li figure::before {
        position:absolute;
        top:0;
        left:0;
        display:block;
        box-sizing:border-box;
        border:2px solid var(--color-main);;
        width:100%;
        height:100%;
        content:"";
        opacity:0;
        transition:opacity 0.3s;
        z-index: 100
    }
 
ul.pdf_file li figure:hover::before {
        opacity:1;
    }
   
   
    

@media screen and (max-width: 767px) {
	ul.pdf_file li{
	width: calc(( 100% - 40px ) / 2 );
	margin:0 20px 20px 0;
	}
	
	ul.pdf_file li:nth-child( 2n ) {margin-right: 0;}
}	

@media print, screen and (min-width: 768px) and (max-width: 1023px) {
	ul.pdf_file li{
	width: calc(( 100% - 60px ) / 3 );
	margin:0 30px 30px 0;
	}
	
	ul.pdf_file li:nth-child( 3n ) {margin-right: 0;}
}	

@media print, screen and (min-width: 1024px) {
	ul.pdf_file{max-width: 900px;}
	ul.pdf_file li{
	width: calc(( 100% - 90px ) / 4 );
	margin:0px 30px 30px 0;
	}
	
	ul.pdf_file li:nth-child( 4n ) {margin-right: 0;}
	
}