The project Pīzhù, meaning margin notes, addresses the common writing challenges faced by Mandarin-speaking students in UK and Irish universities. These challenges stem from linguistic differences, such as the absence of articles in Mandarin, comma splices, the overuse of template phrases, and overly confident claims. Standard grammar checkers and chatbots often rewrite the text, hindering learning and posing academic integrity risks. Pīzhù identifies specific words that might trouble a British marker and provides explanations in both English and Chinese. It also offers subtle nudges for improvement, but crucially, it never rewrites the student's original work. The tool aims to emulate the helpful feedback a teacher would provide in the margins of an essay. Pīzhù integrates a reference checking feature that verifies citations against Google Scholar. The user interface is designed with cultural sensitivity, featuring a friendly mascot and color palette to make feedback less intimidating. Open-source models like Gemma are used, allowing the application to run locally for enhanced privacy and control, ensuring students' work remains on their own machines. The developer tested different sizes of the Gemma model to optimize performance and quality. The tool was developed with a specific user, Joy, in mind, and she found it particularly useful for understanding module assignments.