This course introduces students to the concepts, theories, and interaction techniques in AR/VR/MR/XR. It covers both the fundamental concepts and design theories and the state-of-the-art interaction techniques in the field. In addition, students will work independently or in teams to design, develop, and evaluate AR/VR/MR/XR prototypes. In sum, by the end of the class, students will have a solid grasp of the fundamental concepts, design principles and research gaps in AR/VR/MR/XR and gain hands-on experience in designing and evaluating AR/VR/MR/XR prototypes.