--- /dev/null
+.fade {
+ @include transition($transition-fade);
+
+ &:not(.show) {
+ opacity: 0;
+ }
+}
+
+// scss-docs-start collapse-classes
+.collapse {
+ &:not(.show) {
+ display: none;
+ }
+}
+
+.collapsing {
+ height: 0;
+ overflow: hidden;
+ @include transition($transition-collapse);
+
+ &.collapse-horizontal {
+ width: 0;
+ height: auto;
+ @include transition($transition-collapse-width);
+ }
+}
+// scss-docs-end collapse-classes