@media screen and (max-width: 800px) {
.navbar-nav a{
font-size:0.85em;
}
}
@media screen and (max-width: 1024px) {
.knopka img{
 width:160px;
 height:100px;
 margin:10px;
 }
.knopka{
position:relative;
top:10px;
display:inline-block;
padding:1px;
width:184px;
height:180px;

float:left;
background:#f0f6fc;
background: radial-gradient(circle, #a5b6c7, #fff);
background:-webkit-radial-gradient(circle, #a5b6c7, #fff);
border:2px solid #a5b6c7;
border-radius:10px;
-moz-border-radius:10px;
-webkit-border-radius:10px;
box-shadow:5px 5px 8px 1px rgba(0,0,0,0.5);
text-align:center;
margin:10px;
}
}

@media screen and (max-width: 640px) {
.knopka img{
 width:140px;
 height:80px;
 margin:10px;
 }
.knopka{
position:relative;

display:inline-block;
padding:1px;
width:164px;
height:160px;

float:left;
background:#f0f6fc;
background: radial-gradient(circle, #a5b6c7, #fff);
background:-webkit-radial-gradient(circle, #a5b6c7, #fff);
border:2px solid #a5b6c7;
border-radius:10px;
-moz-border-radius:10px;
-webkit-border-radius:10px;
box-shadow:5px 5px 8px 1px rgba(0,0,0,0.5);
text-align:center;
margin:10px;
}
}