I used to mess with css more.
I still do it for roles/classes that affect the whole app, but for little things now is possible to do this:
from anvil.js.window import jQuery as _S
dom_node = _S(anvil.js.get_dom_node(self))
dom_node.find('[anvil-role="five-columns"]').children().css('column-count', n_columns)
In this case I am dynamically changing the number of columns on all the children of components with the five-columns role.
It is not Anvilli-ish, but it does the job.