OpeningTree is a chess openings book that lets one explore the tree of openings and Crafty engine analysis is available. Chess games can be optionally loaded to check against the book or to just view. Users can make their own side line moves and back up to return to main line. The updated opening book is compiled from 345,000 high rated games from recent years with both players rated 2300 and over. Just touch moves in the list or make moves on the board to see what the response is. 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. Users do not pick an opening to study but start with the full tree. The analyze button on bottom right of board is to flip between viewing the openings move table or seeing Crafty 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 if the users wants to try playing a position out against the engine. OpeningTree's board is accessible to the blind and visually impaired using Voice Over. With Voice Over enabled in device settings, tap on a square for info, double tap to select. Or choose from three move methods. When going forward in a loaded PGN game, moves will be announced on each tap of the forward button. Moves can be marked with colors(red, green, yellow) and colorizing a move at the end of a line will extend the line i.e. add move so it shows later. There is also an option to make a note on a position using the control bar. In the Actions menu if the user has imported a PGN file to the App, for example by opening a PGN file with OpeningTree from a mail attachment or download(long touch on the attachment/download for this option), a game from a PGN file can be loaded and checked against the book. If a user makes a new move, back up to the main line to return to the game. To ensure speed, it will only read/load a max of 5000 games. With bigger files users will only see first 5000 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. Games are saved with opening name as white and black name to spot the lines in each game. 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. The App comes with six PGN game files that can be optionally installed when no PGN files have yet been opened by the App or the user has deleted their PGN files previously opened and likewise has none to access. If this is the case, this option shows when going to Actions -> load PGN. The files contain a mix of famous classical games, a collection of former world champion Gary Kasparov's games and more recent games from two top ranked international tournaments. PGN stands for portable game notation. It's a file extension that can be used with text files that contain chess games in the PGN format. PGN files can be read by apps to display the games in them. If a game is loaded in the App one can then go to 'Actions -> show game data' to view the raw PGN text.