Game Board, Terrain, and the Map

JCiv is played on toroidal grid². That is, the game board is a regular rectangular grid of CELLs, but the top of the grid meets the bottom and the left side meets the right side. A UNIT that moves off the top of the board will find itself on the bottom, etc. The DIMENSIONS of the board (number of CELLs in each direction before wraparound) are specified by two parameters, $s_{X}$ and $s_{Y}$, that are set during GAME INITIALIZATION.