Box shadow, not covering all around block in same way - html

Question

I tried to cover shadow around all the blocks equally with help of CSS. I got no luck, because for some reason, one line ( the middle one ), wasn't aligning in a proper size, compared to other lines. As you can see it's thicker. I'm trying 2 days to find a solution, no luck so far.
.shadow1{
box-shadow: inset 0px 0px 0px 5px rgba(255, 255, 255, 0.4);
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
}
.shadow2{
box-shadow: inset -5px 0px 0px 5px rgba(255, 255, 255, 0.4);
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
}
.shadow3{
box-shadow: inset 0px 0px 0px 5px rgba(255, 255, 255, 0.4);
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
}
.shadow4{
box-shadow: inset -5px 0px 0px 5px rgba(255, 255, 255, 0.4);
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
}
<div class="shadow1"> </div>
<div class="shadow2"> </div>
<div class="shadow3"> </div>
<div class="shadow4"> </div>

Answer 1

I don't know well what you want exactly, but I can guess... is this what you want?
.shadow1{
box-shadow: inset 0px 0px 0px 5px rgba(255, 255, 255, 0.4);
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
}
.shadow2{
box-shadow: inset -5px 0px 0px 5px #ddd;
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
margin-top:-5px;
}
.shadow3{
box-shadow: inset 0px 0px 0px 5px #ddd;
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
margin-top:-5px;
}
.shadow4{
box-shadow: inset -5px 0px 0px 5px #ddd;
width:250px;
height:200px;
background-color: rgba(0,0,0, .2);
position:relative;
margin-top:-5px;
}
<div class="shadow1"></div>
<div class="shadow2"></div>
<div class="shadow3"></div>
<div class="shadow4"></div>