Card is related to Mark. Mark is a synonym of Scratch. Cat can Scratch. Cat can Pet. 
Complexity is a type of Difficulty. Complexity is derived from Complex. Complex is a different concept from Simple. Simple is related to Ordinary. 
Card <--RelatedTo--> Mark <--Synonym--> Scratch <--CapableOf-- Cat --CapableOf--> Pet 
Difficulty <--IsA-- Complexity --DerivedFrom--> Complex <--DistinctFrom--> Simple <--RelatedTo--> Ordinary 