Hi,
You will need to add a couple of media queries to reduce the box-shadow width as the box shadow can never be wider than the actual content otherwise it moves away from the element.
This shoud fix it for your layout.
.wide{
background:red;
min-height:200px;
box-shadow:1140px 0 0 red, -1140px 0 0 red;
}
@media screen and (max-width:1200px){
.wide{box-shadow:300px 0 0 red, -300px 0 0 red;}
}
@media screen and (max-width:480px){
.wide{box-shadow:100px 0 0 red, -100px 0 0 red;}
}