All solutions

What I find the most intimidating task in this challenge is the how to separate the 3 filter buttons out of the todo list in mobile view. My solution just looks nearly to the design, but without the shadow at the bottom of todo list. The second most intriguingly task is to style the border of checkmark linear gradient because CSS does not support it natively. I'm interested in how you guys solve these 2 styling challenges.

• I'm looking forward to hearing your suggestions on the implementations of function handling replies (add, update, delete, vote) in CommentContext. Can it be improved?
• I'm also curious about the way you guys structure your comment and replies element in the markup because I'm not sure if mine is optimized.
• Btw, I had trouble using json-server in production (CORS), so I decided to use Firebase as backend. I realized that listening to realtime changes in Firebase make the handler functions in CommentContext a lot easier, and the amount of action in reducer is significantly reduced (see branch dev vs master). I'm not sure if there's anything to concern because I'm not familiar with this behavior of Firebase.