- Simple selectors: type, universal, class, ID, attribute, pseudo-class - Compound selectors: all parts must match - Complex selectors with combinators: descendant, child, adjacent/general sibling - Selector list matching (comma-separated) - Specificity calculation (a, b, c) with Ord implementation - Rule collection: gather matching rules sorted by specificity and source order - Declaration collection with !important separation - Right-to-left matching for correct combinator evaluation - All attribute operators: exact, includes, dash-match, prefix, suffix, substring - 34 tests covering all selector types, combinators, specificity, and rule collection Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>