Final answer:
The sentence "My cat is winding around my legs." is a simple sentence as it has one main clause and expresses one idea.
Step-by-step explanation:
When analyzing the sentence "My cat is winding around my legs," we find that it contains one subject, "My cat," and one predicate, "is winding around my legs."
There are no additional independent or subordinate clauses within this sentence. Hence, it is a simple sentence because it has one main clause and one idea expressed.