Drive-by here, but can we either get rid of this mixin or change it to accept a single argument? (i.e. `.box-shadow( 0 0 4px #555 )`. We don't actually need the prefixes if we are only supporting ie9+, so I think it would be best to get rid of it.

Also, this looks better if it's moved down vertically, has a negative spread radius, and uses faded black (again, rgba is cool since ie9+) `0 4px 10px -5px rgba( 0, 0, 0, 0.8 );`