_stacked.scss in font-awesome-sass-6.0.0

- old
+ new

@@ -1,23 +1,24 @@
-// Stacked Icons
+// stacking icons
 // -------------------------
 
 .#{$fa-css-prefix}-stack {
   display: inline-block;
   height: 2em;
   line-height: 2em;
   position: relative;
-  vertical-align: middle;
-  width: ($fa-fw-width*2);
+  vertical-align: $fa-stack-vertical-align;
+  width: $fa-stack-width;
 }
 
 .#{$fa-css-prefix}-stack-1x,
 .#{$fa-css-prefix}-stack-2x {
   left: 0;
   position: absolute;
   text-align: center;
   width: 100%;
+  z-index: var(--#{$fa-css-prefix}-stack-z-index, #{$fa-stack-z-index});
 }
 
 .#{$fa-css-prefix}-stack-1x {
   line-height: inherit;
 }
@@ -25,7 +26,7 @@
 .#{$fa-css-prefix}-stack-2x {
   font-size: 2em;
 }
 
 .#{$fa-css-prefix}-inverse {
-  color: $fa-inverse;
+  color: var(--#{$fa-css-prefix}-inverse, #{$fa-inverse});
 }