When working with complex CSS selectors that include multiple nested pseudo-selectors like `:is()`, `:where()`, `:not()`, and `:has()`, maintain consistent formatting and consider breaking long selector chains for better readability. This is particularly important in Svelte components where selectors may need `:global()` wrappers. For complex nested selectors, consider adding multiple selector options within pseudo-selectors to improve maintainability: ```css /* Good: Multiple selectors within :is() for flexibility */ div :is(:global(.class:is(span:is(:hover)), .x)){} /* Instead of: Single complex nested chain */ div :is(:global(.class:is(span:is(:hover)))){} ``` This approach makes selectors more maintainable and allows for easier extension when additional selector variants are needed.