Caspian.css works fine, but it requires the css engine to do a lot of busy-work determining whether rules are valid in cases where they aren't. This is because the css engine must look up the entire scenegraph branch for each node that matches on of the CSS selectors in caspian.css, to see if a parent (or grandparent) matches the rest of the rule. Using child selectors makes it clear to the CSS engine that it need not go up the entire scenegraph branch, as the parent must be the direct parent, not just any descendent. This should theoretically improve performance considerably, particularly in cases such as TableView.