Leet Chess has a large set (about 220K) of the most popular open-source puzzles from lichess puzzles databases for you to work on at your fingertips. Here are some of the main features:

- Puzzles creation based on a search
Users can search for puzzles based on ratings, openings, tactical themes, pieces, and more.

- Tracking puzzle progress/accuracy
Users can track their progress/accuracy in solving puzzles, and the app records which puzzles they have solved and which they are still working on.

- Reset result
The app allows users to reset their results for specific puzzles. This means that if a user solves a puzzle but wants to try again to improve their time or score, they can reset the puzzle's results and try again. This feature is especially useful for users who want to challenge themselves and improve their tactical skills.