Less: inset shadow on top/bottom side

gistfile1.css

.shadow-top-inset(@length: 15px, @color: gray) {
  box-shadow: inset 0 @length @length -@length @color;
}
.shadow-bottom-inset(@length: 15px, @color: gray) {
  box-shadow: inset 0 -@length @length -@length @color;
}
.shadow-top-bottom-inset(@length: 15px, @color: gray) {
  box-shadow:
    inset 0 @length @length -@length @color,
    inset 0 -@length @length -@length @color;
}

body {
  margin: 0;
}

#block {
  background: rgb(213, 211, 208);
  height:150px;
  padding:8px;

  .shadow-top-bottom-inset;
}

#block2 {
  background: rgb(242, 242, 242);
  height: 150px;
}

#block3 {
  background: rgb(0, 174, 238);
  color:white;
  height:150px;
  padding:8px;
  
  .shadow-top-inset;
}