OpeningTree is a chess opening book that lets users navigate the tree of openings and Stockfish 10 engine analysis is available including multiple lines of analysis if the user wants. Chess games can be loaded from PGN game files to check against the book or to just use the app as a PGN reader. The opening book is made from about 345,000 games from the last ten years with both players rated 2300 and up. The stats next to moves are how many games resulted in wins, draws or losses. The concept or