← Guide

Engine ▸ Analysis (Ctrl+E) turns on and off the analysis of the position on the board. The Engine panel shows the score — always from White's side: positive is good for White —, the depth and the best line. The bar beside the board shows the same score. Click the score to show it another way, in turn: absolute (from White's side, as the engine gives it), for the side to move, the side to move's chances, and the judgement a chess book prints (=, ⩲, ±, +− and their opposites, from White's side). The dot before the value is its unit: half white and half black for White's side, the colour of the side to move for its own; the book's symbols have none. The chances are the expected score in per cent: what that side brings home on average from such a position, a win counting 1 and a draw ½ — 50% is level, a pawn up about 59%, three pawns about 75% (the curve lichess uses, and the bar beside the board). The tooltip gives all four at once; the choice is saved with the project. Beside the score, in the same box, the course of the game: a dot for each move whose evaluation is known (what the engine found there, or the game's own evaluations, as lichess writes them), joined by a line, over the midline of a balanced game. The height grows with the advantage more slowly than it: half a pawn already shows, a pawn is close to half way, two are less than twice as far, ten and a mate reach the edge. White's advantage goes towards White's side of the board, as in the bar, so the graph turns with the board; the move on the board is marked. Click a dot to go to that move. Twenty moves fill the width; a longer game is squeezed into it, never scrolled.

To see where the line leads, press and hold the eye beside Stop: while you hold it, the board shows the position at the end of the engine's line, as if all its moves were played, and it follows the engine: when the engine finds another line, the board moves to where the new one ends. Let go and your position comes back. Over that position, violet arrows show the plans the line holds: how a piece travelled to get there (a knight's route, a rook lift, the queen changing wing), the king marching in an endgame, a pawn running or breaking through. An arrow that turns passes through the squares where the piece stopped. Exchanges and moves forced by a check are not plans, so a line made only of them shows no arrows.

Pragma Chess comes with Stockfish, and works with any UCI engine.

• Engine ▸ Switch Engine chooses among the engines of this computer. The engine icon of the toolbar drops down the same list.
• Engine ▸ Manage Engines… adds, edits and removes engines. Detect Engines finds the ones installed on the computer; Use This Engine switches to the selected one.
• Computing Power, in the same window, is how much of the computer the engine may use while it analyzes, from Minimum (3% of the processor) to Full (all of it, no limit); Medium, 10%, is where every engine starts. The engine is just as strong at every level, only slower: it gets fewer threads, a lower priority and, on Linux and Windows, a cap on its share of the processor, so the fans stay quiet and the rest of the computer stays free. Threads, if you set them, win over the level's.

The engine in use is part of the project.