Function of infinitive clause in a sentence

Question

I am having a confusion with a sentence ;

[To look at], the helmet resembles nothing so much as a novelty head massage gadget with several spidery arms.

What is the function and type of "to look at" in this sentence? I know infinitive phrases often used as noun,adverb,adj etc but can't figure this one.

Answer 1

Here the phrase "To look at" modifies the verb "resembles". Specifically, it tells the reader that the similarity is visual, not say a similarity of sound or function. Thus the phrase functions as an adverb.