I realize that you are trying to get people to actually learn code, but there is a large chunk of these exercises that could be made quicker by cut and pasting.
I am not saying calling it a stackoverflow section, but having it available early on would really speed up coding on a phone.
Love what you have done so far. Recommendations for next steps:
Allow users to submit challenges, like “have your screen look like this at the end” and allow people to solve them for points. Maybe needs moderation though.
Can’t wait to see what you guys do next.