Nuclides are parts of the stylesheet source that are not directly useable on their own. This could be mixins, variables like colors and sizes, or settings.
To mark a variable or mixin as a nuclide, annotate it with the @nuclide tag, followed by the name of the nuclide.
Special forms are @color and @mixin.
@include clearfix();
@include clearfix(important);@include triangle(up, 20px, 50px, red);
@include triangle(down, 40px, 20px, red);
@include triangle(left, 50px, 20px, red);
@include triangle(right, 100px, 20px, red);