This is really cool, nice work!<p>A couple of minor criticisms (as an intermediate Vim user):
- I felt like it was too easy to just stare at the key instruction on the top left and just ignore how you're navigating the block of text itself. As you are letting people know what commands are being introduced in the next lesson, maybe they should only be shown if the student wants a hint?
- It seems like the only way to go to the next lesson on completion (without using the mouse) is to tab once then hit enter. Maybe that could be a keyboard command as well? `n` maybe?
Looking briefly, I'd suggest prioritizing useful information to the top of the page. For example on 'Bread and Butter' the useful stuff, the key bindings, are at the bottom and the top of the page is a wall of text that probably would usefully fill space in a live classroom or video context, but adds a lot of noise in a text based context.<p>To put it another way, the user is a reader and hunting useful information requires parsing through the text. The more there is that isn't useful the more work the reader has to do and the more likely misunderstandings are.<p>It might also be useful to have the key bindings available as an interactive element in the interface. Even considering how that would effect the bread and butter page might be a useful exercise regarding how information might be organized.<p>Good luck.