make the computer more or less challenging. In harder games, above level 10, the human player starts with fewer neutral cities nearby to conquer and takes twice as long to produce any particular unit than the computer. The map is a horizontally oriented rectangle divided into a grid of unit-sized rectangles. Measured by playable grid units, the player(s) can choose a map that is small (48 x 32), medium (96 x 64), or large (124 x 96). The top and sides of the map do not 'wrap around', i.e., units cannot transit the edges to go from the right to the left side of the map, the top to the bottom of the map, or vice versa. The 4.x versions include a re-written map generation system with three terrain settings: "wet" (mostly islands), "dry" (land including some bodies of water), and "normal" (mostly larger islands). Game play Each player starts out in control of one city. All other cities are hidden and are neutral. The entire map - besides the player's city and the adjacent eight grid units - is black and must be discovered by sending units into it. The goal of the game is to capture cities and use them to produce additional military units to capture more cities. The game is won when one player controls all of the opponent's cities. Cities also offer the ability to refuel aircraft and repair ships. The game is turn-based. A turn is completed when all of the player's units have an order given in a previous turn or have been given orders in the current turn. During the turn, players may also change what units their cities are producing. A fog of war system is used, in that enemy units that are not adjacent to an enemy unit are invisible to the player. Enemy units become visible if they are discovered by the player in the course of his or her turn, until contact is lost and the enemy unit is no longer visible. Units All units may attack up to two times per turn. If you are playing against the computer you can extend this to however many moves would be left to the unit if you had not attacked by clicking the "W" (wake) key. Tanks and ships (including submarines) with a strength greater than one suffer a reduction in their number of moves per turn if they