@media screen and (max-width: 850px){
	#BooksBox{width: 90%;}
	#Topics{ width:42%;}
#Books{ width:57%;margin-left:43%;}
#Topics{border-radius: 20px 0 0 20px;}
#Books{ border-radius: 0 20px 20px 0;}
#Topics button:first-child{border-top-left-radius: 20px;}
#Topics button:last-child{border-bottom-left-radius:  20px;}
.but:first-of-type{border-top-right-radius:  20px;}
.but:last-child{border-bottom-right-radius:  20px;}
  #Topics button{padding: 7px 10px;}
  .but{padding: 20px 10px 7px 60px;}
}
@media screen and (max-width: 650px){
    #BooksBox{ font-size:1.3em;}
    #labelBook2{display:block;}
#labelAutor{display:block;margin-left:0;margin-top:1em;}
#labelBook{display:none;}

#Topics{
	position: static ;
	width:100%;
	border-radius: 20px;
}
#Books{ 
width:100%;
margin: 0;
border-radius: 20px;
}
#download_button:first-child{ border-top-left-radius: 20px;}
#Topics button:first-child, .but:first-of-type{border-top-left-radius: 20px;border-top-right-radius:  20px;}
#Topics button:last-child, .but:last-child{border-bottom-left-radius:  20px;border-bottom-right-radius:  20px;}
}