Can I say "great at" instead of "great for"?

Native speaker’s answer
Rebecca
Using "great at" instead of "great for" would change the context of the sentence! "Great at" is often used when a person is good at doing something. The phrase "great for" is used when an object has a good use for something. Ex: This tool is great for screwing nails in securely. Ex: James is great at fixing cars. Ex: This light is great for seeing at night.