backward/backwards

I've got a quiz question for you. Which of the following statements is correct? "I put my pants on backward." "I put my pants on backwards." I fooled you. It was a trick question. Actually, both are correct.

Why? The word is used as an adverb in each instance. It's modifying the verb telling how I put my pants on. If that's the case, either one is perfectly acceptable.

In the case of an adjective, you must use "backward" only. For example, you would say, "The golf ball took a backward roll." The word is now modifying the noun "roll." No, "roll" in this context is not an action, it's a thing. Doesn't it sound stupid to say, "The golf ball took a backwards roll"? Duh!

Come to think of it, I'm not sure why I put my pants on backward. That's really strange. I'm not sure I want to know now.