I Built a Chess Tool That Turns My Lost Games Into Personalized Puzzles

One thing I've noticed about improving at chess is that solving puzzles is useful, but learning from your own mistakes is important too.
When I lose a game on Chess.com or Lichess, I can analyse it to understand what went wrong. But I wanted an easier way to turn those mistakes into something I could practise later.

So I decided to build a chess tool around that idea.
What does it do?
The app currently has two main features.

1. Personalized chess puzzle builder You can import your lost games from Chess.com or Lichess and use them to create puzzles based on your own games. Instead of practising only with generic puzzles, you can revisit positions from games you've actually played.

1. Position analysis with adjustable playing strength The app also includes a chessboard for analysing individual positions.

You can configure the engine to a preferred playing-strength level, allowing you to explore positions without always relying on the strongest possible engine play.
This feature focuses on analysing individual positions rather than analysing an entire game.
Why did I build it?
I wanted a practical way to connect analysing my mistakes with practising them.
The idea is simple: if I repeatedly make certain mistakes in my own games, I should be able to revisit those positions and work on understanding them.
I built this tool to make that process easier.
Try it out
The app is live, and I'm looking for people who enjoy playing chess and are willing to try it.
♟️ Try the app: https://chess-puzzle-builder.vercel.app/
I'd especially appreciate feedback on these questions:
Is creating puzzles from your own lost games useful?
Would you use an adjustable-strength engine when analysing positions?
What features would make this tool more useful for improving at chess?
Did you encounter any bugs or confusing parts of the interface?
I'm still working on improving the app, so honest criticism is welcome.
Thanks for reading!