CSS - 垂直居中 (SCSS)

gistfile1.txt

.foo {
  $width: 500px;
  $height: 300px;
  width: $width;
  height: $height;
  position: absolute;
  top: 50%;
  left: 50%;
  margin-left: - $width/2;
  margin-top: - $height/2;
  background-color: gray;
}