Nice idea--I could've used this back in school. Couple of suggestions: 1. Consider adding Next and Previous buttons, so help the user navigate a fixed path to

Nice idea--I could've used this back in school. Couple of suggestions: 1. Consider adding Next and Previous buttons, so help the user navigate a fixed path to study a topic. 2. Consider adding a left pane with a nested tree of topics/lessons showing where you're at. That would give a sense of progress as the user move forward in a topic, and it'd also let the user easily skip out of order to another topic/lesson.