SOURCES AND PROVENANCE
Checked 21 October 2026

1. Pawnpetal official App Store listing
https://apps.apple.com/us/app/pawnpetal-chess-play-learn/id6811392880
Supports the limited statement that the app advertises PGN import and study of variations, and its iOS/iPadOS requirement. Does not establish compatibility with these files or a tested interface path.

2. python-chess core API documentation
https://python-chess.readthedocs.io/en/latest/core.html
Reference for Board.is_valid, legal_moves, is_pinned, is_checkmate and is_stalemate. Actual checks are recorded in chess_validation.json.

3. python-chess PGN documentation
https://python-chess.readthedocs.io/en/latest/pgn.html
Reference for setup positions, FEN tags, PGN parsing/writing and error reporting.

4. Locally installed DejaVu font license
/usr/share/doc/fonts-dejavu/copyright
Copied into font_license.txt. The font license permits use and embedding/distribution subject to its notices. No third-party puzzle positions or puzzle text were used.

Validation dependency
python-chess 1.999 / chess module 1.11.2, installed from https://pypi.org/simple only. No engine binary or unknown executable was downloaded.
