PhysicsGraph is easily the most effective and engaging learning tool I have had the pleasure of using. The lessons are fun, informative, and the perfect length to fit into a coffee break. Moreover, their spaced repetition system ensures that you never forget the content of these lessons and can use the knowledge to seamlessly build up to more advanced topics. The founding team is also top notch, responding instantly to user feedback and constantly adding new content. Overall, I could not recommend PhysicsGraph more highly. It is truly an outstanding product.