first commit

user/plugins/problems/scss/mixins/_shadow.scss

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+// Component focus shadow
+@mixin control-shadow($color: $primary-color) {
+  box-shadow: 0 0 0 .1rem rgba($color, .2);
+}
+
+// Shadow mixin
+@mixin shadow-variant($offset) {
+  box-shadow: 0 $offset ($offset + .05rem) * 2 rgba($dark-color, .3);
+}