I don't mind your usage of "superficial thinking". I've been thinking for a little while and I can't seem to come up with a more idiomatic and concise alternative. While "shallow" is the antonym of "deep", I don't think that relationship extends to well into that set, metaphoric usage. Of course, "shallow thinking" would be understood as you intended it to be, but it sounds rather awkward to my ear. I would even prefer terms such as "rudimentary" or "simple" to "shallow".
Thank you, perpend and Rhye
I just don't understand why "think deep" is grammatical. It's supposed to have an adverb to follow a verb instead of using an adjective. Same thing happens when I saw "drive safe". It's supposed to be "drive safely". Why?
Yes, you are quite correct—neither "think deep" nor "drive safe" are grammatical. "Thinking" is a noun which would would take an adjective like "deep". If you were to use the verb "to think" instead, then you would have to use the adverb "deeply" as you expected. There are some cases when, in colloquial English, we overlook such uses of commonly used adjectives in lieu of more obscure adverbs (though I doubt many of these forum users would admit that ), but I do not find this to be one of these cases, in spite of what perpend said. And, again, in formal English this sort of replacement would be completely impermissible.
"Drive safe" is another such example of the phenomenon I described. Only "drive safely" is correct, in spite of what countless conversations might imply.