Responsive Hexagon grid with a border

Question

http://codepen.io/web-tiki/pen/HhCyd

I am working using the above pen from a similar question. I was able to edit the size of the hexagon editing the width property and padding but I wanted to add a border to the hexagon, I was able to the left and right of the hexagon by adding a border and editing the box-sizing of the category li div element but was not able to get it for the other sides of the hexagon by editing the category li element.

body{
  font-family: 'Open Sans', arial, sans-serif;
  background:rgb(0, 0, 0);

}
*{
  margin:0;
  padding:0;
}
#categories{
  overflow:hidden;
  width:90%;
  margin:0 auto;
}
.clr:after{
  content:"";
  display:block;
  clear:both;
}
#categories li{
  position:relative;
  border-style: solid;
  border-width:10px; 
  list-style-type:none;
  width:27.85714285714286%; /* = (100-2.5) / 3.5 */
  padding-bottom: 32.16760145166612%; /* =  width /0.866 */
  float:left;
  overflow:hidden;
  visibility:hidden;

  -webkit-transform: rotate(-60deg) skewY(30deg);
  -ms-transform: rotate(-60deg) skewY(30deg);
  transform: rotate(-60deg) skewY(30deg);
}
#categories li:nth-child(3n+2){
  margin:0 1%;
}
#categories li:nth-child(6n+4){
  margin-left:0.5%;
}
#categories li:nth-child(6n+4), #categories li:nth-child(6n+5), #categories li:nth-child(6n+6) {
  margin-top: -6.9285714285%;
  margin-bottom: -6.9285714285%;

  -webkit-transform: translateX(50%) rotate(-60deg) skewY(30deg);
  -ms-transform: translateX(50%) rotate(-60deg) skewY(30deg);
  transform: translateX(50%) rotate(-60deg) skewY(30deg);
}
#categories li:nth-child(6n+4):last-child, #categories li:nth-child(6n+5):last-child, #categories li:nth-child(6n+6):last-child{
  margin-bottom:0%;
}
#categories li *{
  position:absolute;
  visibility:visible;
}
#categories li > div{
  border-style: solid;
  border-width: 5px;
  box-sizing:border-box;
  width:100%;
  height:100%;
  text-align:center;
  color:#fff;
  overflow:hidden;

  -webkit-transform: skewY(-30deg) rotate(60deg);
  -ms-transform: skewY(-30deg) rotate(60deg);
  transform: skewY(-30deg) rotate(60deg);

  -webkit-backface-visibility:hidden;

}

/* HEX CONTENT */
#categories li img{
  left:-100%; right:-100%;
  width: auto; height:100%;
  margin:0 auto;   
}

#categories div h1, #categories div p{
  width:90%;
  padding:0 5%;
  background-color:#008080; background-color: rgba(0, 128, 128, 0.8);
  font-family: 'Raleway', sans-serif;

  -webkit-transition: top .2s ease-out, bottom .2s ease-out, .2s padding .2s ease-out;
  -ms-transition: top .2s ease-out, bottom .2s ease-out, .2s padding .2s ease-out;
  transition: top .2s ease-out, bottom .2s ease-out, .2s padding .2s ease-out;
}
#categories li h1{
  bottom:110%;
  font-style:italic;
  font-weight:normal;
  font-size:1.5em;
  padding-top:100%;
  padding-bottom:100%;
}
#categories li h1:after{
  content:'';
  display:block;
  position:absolute;
  bottom:-1px; left:45%;
  width:10%;
  text-align:center;
  z-index:1;
  border-bottom:2px solid #fff;
}
#categories li p{
  padding-top:50%;
  top:110%;
  padding-bottom:50%;
}


/* HOVER EFFECT  */

#categories li div:hover h1 {
  bottom:50%;
  padding-bottom:10%;
}

#categories li div:hover p{
  top:50%;
  padding-top:10%;
}

Answer 1

This worked pretty well for me, hope it will be helpful for you as well.

<div class="hexagon"></div>

.hexagon {
  position: relative;
  width: 300px; 
  height: 173.21px;
  background-color: #64C7CC;
  margin: 86.60px 0;
  border-left: solid 5px #333333;
  border-right: solid 5px #333333;
}

.hexagon:before,
.hexagon:after {
  content: "";
  position: absolute;
  z-index: 1;
  width: 212.13px;
  height: 212.13px;
  -webkit-transform: scaleY(0.5774) rotate(-45deg);
  -ms-transform: scaleY(0.5774) rotate(-45deg);
  transform: scaleY(0.5774) rotate(-45deg);
  background-color: inherit;
  left: 38.9340px;
}

.hexagon:before {
  top: -106.0660px;
  border-top: solid 7.0711px #333333;
  border-right: solid 7.0711px #333333;
}

.hexagon:after {
  bottom: -106.0660px;
  border-bottom: solid 7.0711px #333333;
  border-left: solid 7.0711px #333333;
}

For image inside hexagon use this:

<div class="hexagon">
  <div class="hexTop"></div>
  <div class="hexBottom"></div>
</div>

.hexagon {
  position: relative;
  width: 300px; 
  height: 173.21px;
  margin: 86.60px 0;
  background-image: url(http://you_image_url.jpg);
  background-size: auto 334.8632px;
  background-position: center;
  border-left: solid 5px #333333;
  border-right: solid 5px #333333;
}

.hexTop,
.hexBottom {
  position: absolute;
  z-index: 1;
  width: 212.13px;
  height: 212.13px;
  overflow: hidden;
  -webkit-transform: scaleY(0.5774) rotate(-45deg);
  -ms-transform: scaleY(0.5774) rotate(-45deg);
  transform: scaleY(0.5774) rotate(-45deg);
  background: inherit;
  left: 38.93px;
}

/*counter transform the bg image on the caps*/
.hexTop:after,
.hexBottom:after {
  content: "";
  position: absolute;
  width: 290.0000px;
  height: 167.4315780649915px;
  -webkit-transform:  rotate(45deg) scaleY(1.7321) translateY(-83.7158px);
  -ms-transform:      rotate(45deg) scaleY(1.7321) translateY(-83.7158px);
  transform:          rotate(45deg) scaleY(1.7321) translateY(-83.7158px);
  -webkit-transform-origin: 0 0;
  -ms-transform-origin: 0 0;
  transform-origin: 0 0;
  background: inherit;
}

.hexTop {
  top: -106.0660px;
  border-top: solid 7.0711px #333333;
  border-right: solid 7.0711px #333333;
}

.hexTop:after {
  background-position: center top;
}

.hexBottom {
  bottom: -106.0660px;
  border-bottom: solid 7.0711px #333333;
  border-left: solid 7.0711px #333333;
}

.hexBottom:after {
  background-position: center bottom;
}

.hexagon:after {
  content: "";
  position: absolute;
  top: 2.8868px;
  left: 0;
  width: 290.0000px;
  height: 167.4316px;
  z-index: 2;
  background: inherit;
}