Polymorphism and Extension Functions

extension functions are a mystery in there that I haven't figured out and it's like, seems so simple. And yet what you can do with it now is more. It's almost like it's duck typing because you're saying, okay, I'm going to assume that this function exists for this thing, but you have to make it up. Now it seems like we've come back to type classes. Yeah. Well, and the thing that doesn't freak me out about this now is that I'm looking at all this stuff as variations of polymorphism, right? So you're going, okay, maybe this is a variation of polymorphism. What are we trying to achieve here?