I play a little guitar (over 35 years lol), and I have always dabbled in piano, never seriously enough until recently, when I decided I wanted to get somewhat better technically.
I also wanted to able to play nice chord progressions and be able to edit and tweak these progressions with a tool. That led me to building pianotry, more for myself and my daughter (who has started playing and plays by ear also and quite well).
I figure the best way to start is trying to play stuff that sounds good, and only go deeper if you want to, no sense letting the theory get in the way of the sound initially.
I also figured it would be cool to make a jsfiddle/codepen variant for piano progressions, which allows you to build and share your ideas.
I also have a next chord suggester for making progressions.
So this is my first pass at a little tool to do this.
I am trying to bake as much in as simply as I can.
I know there are many piano apps and sites out there, but this is just me building through my lens.