OpeningTree is a chess opening book that lets users explore 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 to check against the book or to just view. The opening book is compiled from 240,000 high rated games from recent years with both players rated 2300 and over. The numbers next to moves indicate how many games resulted in wins-draws-losses. The idea comes from computer opening books as if we can open up the book and see what those moves are that people play in response to opening positions. The analyze button on bottom of app is to flip between viewing the openings move table or seeing Stockfish engine analysis. +1.00 score means white is ahead a pawn. -1.00 score means black is ahead a pawn. There is a move now button to make the engine play the current best move. In the Actions menu PGN game files can be opened. The app also comes with some installed PGN files on Open App's PGN menu item. To ensure speed, it will only read/load a max of 2500 games. With bigger files users will only see first 2500 games. There is a Save Board to PGN option on the Actions menu. It saves the current moves to openings-user-games.pgn, a file OpeningTree will create on first save. . This allows the users to export data out of the App such as favorite lines with the mail games option when looking at a game list.