.responsive {
border-collapse:collapse;
border-spacing:0;
margin:0 auto 40px;
}

@media screen and (min-width:800px){
.responsive {width: 80%;}

.responsive thead th {
height:50px;
line-height:50px;
border:1px solid #ddd;
background: Orange;
color:#fff;
}

.responsive tbody td {
height:40px;
line-height:40px;
border:1px solid #ddd;
}
}

@media screen and (max-width:799px) {
.responsive, thead, tbody, th, tr, td {display: block;}

.responsive {width:90%;}
}

div#box-2 {
  /* ... */
  min-width:   20px;
  min-height:  20px;
  max-width:  500px;
  max-height: 500px;
  margin: 0 auto;
}