A Cood represents a 2 dimensional integer coordinate within a tile grid system. This has current been implemented for Hexs and Squares, while triangles is the third possible regular tile system. A SqGrid Cood represents either a tile centre, a tile side or a tile vertex. This is the same for a Hex Grid except that not all values are legal Cood values on a HexGrid. This system allows river and naval units to move along the tile sides. The axis are named xi and yi to distinguish them from the x and y of a Vec2. On a Hex grid there is not a simple 1 to 1 mapping between the Cood components and the Vec2 components.