Several years ago (around 2015), I also developed a typing learning web application. It was inspired by another application that had originally been developed for Windows 95 - with that app, I learned how to type. So in 2015, I decided to implement a web-based version of it.
However, I just checked out keybr.com and have to say - it's a much better system for learning to type! As of today, I now realize I have a huge problem with the letter "q" - I had never noticed that before! ^^