The coronavirus pandemic forced teachers to use online meeting software to teach courses remotely. However, without on-site supervision from teachers, students can get distracted and lead to learning inefficiencies. Distraction also leads to low interaction, and teachers may lose enthusiasm in teaching. In addition, social interaction is necessary for campus life. To address these problems, we present InteractDiff, a 3D sandbox game to improve the online teaching experience and interactivity. We designed several school scenarios and mechanisms where users act as an avatar inside to imitate real-life interactions in university. Our preliminary study shows potential feasibility and positive feedback from users.