Data sources
All chess content is drawn from open-licensed community sources and attributed here. Most is committed into the build; the Opening Explorer also reads some of it live.
Openings
Opening names and the master-game statistics behind the Opening Explorer.
- Lichess chess-openingsCC0-1.0ECO codes and standard opening / variation names.
- Lichess opening explorer — masters gamesCC0-1.0Live master-game move popularity and win/draw/loss results, read at play time through our own server proxy.
Puzzles
Every tactical and endgame puzzle is selected from the open Lichess puzzle database.
- Lichess puzzle databaseCC0-1.0Puzzle positions, solutions, themes, and ratings.
Opening Explorer commentary
The Explorer’s Commentary tab reads prose live from the Wikibooks Chess Opening Theory book — nothing is committed to the repo.
- Wikibooks — Chess Opening TheoryCC BY-SAThe ideas behind each line, fetched live per position.
Lessons
Lesson material is adapted — reworded and restructured — from open-licensed encyclopedic sources.
- Wikibooks — ChessCC BY-SA 4.0Tactics and endgame chapters adapted into guided lessons.
- Wikipedia — chess articlesCC BY-SA 4.0Individual tactic and checkmate-pattern articles (fork, pin, back-rank mate, …) adapted into guided lessons.