Center annotation symbol

The center first refers to d4, e4, d5, and e5, the four central squares, although analysis may also consider a wider central area. Controlling the center means being able to occupy, attack, or pass through these squares with pawns and pieces.

The ⊞ sign summarizes that one side has a center-control advantage. In Portable Game Notation (PGN), the text format for games, Numeric Annotation Glyphs (NAGs) $48-$53 distinguish the side and three degrees of strength. Even values refer to White and odd values to Black; some programs repeat ⊞ to display a larger advantage.

The symbol does not explain why the control exists. It may come from central pawns, active pieces, or pressure on key squares. It is also not the same as a direct attack. Central control may support a later offensive, but it is a separate positional feature in the symbol system.