The idea of an automated coach is quite interesting, however it would be a very involved effort to match the level of a human mentor that some of the expensive websites provide. Its nice that it suggests problems I should be solving and give hints based on time so I don't get stuck.
Definitely something I will use the next time I have to prepare for an interview. Seems like a much better source than geeks4geeks.
I really like this approach of gamified interview prep, kind of like Duoling style learning. Practicing for interviews is hard, and this makes it a little more fun :) Good luck!
An automated coach kind of sounds cool, but why limited to programming interviews?