Editing Imperium (board game) (section)

== Game play ==
Game play consists of a series of wars fought between the two players until one player completely conquers the map (or the other player concedes).  A single war may be fought over an evening, but a "Campaign" of multiple wars can take several weeks to complete.  Starting positions for each new war are determined by the outcome of the last war, modified by rules for events during peacetime. Each war consists of a sequence of turns with alternating player-turns, each consisting of multiple phases. Each turn represents a period of two years. The game includes an economic system in which the units on each side are produced and maintained. The Terran income is based on what type of world the player currently possesses, and whether it is connected by friendly jump paths to [[Sun|Sol]]. The Imperial income on the other hand has a fixed budget, but an increment for each connected outpost and world.

Each player turn begins with an economics phase. The player then performs movement and combat, followed by the opposing player's reaction movement and combat phase, and finally the second movement and combat phases. Then the other player repeats the same sequence and the turn ends.<ref name="wd16" /> A "Glory Point" tally earned by the Imperium tracks who is having the upper hand in any given war. Points are gained for conquering worlds and lost for their conquest by the Terrans. A habitable world is worth four Glory Points and an outpost world is worth one.  If at the end of a turn the Glory Point total has reached the amount necessary for victory, then the war is ended with the Imperium declaring victory. If the total drops sufficiently, the war instead ends with Terra declaring victory. The players thus do not get to choose how long to wage a particular war. The range between the amount required for Imperium or Terran victory begins to shrink after turn three, representing the decreasing appetite for continued hostilities.

Combat is somewhat abstracted, with the ships being lined up off map.<ref name="wd16" />  All combat begins at long range.  On subsequent combat rounds a die is rolled to see which player gets to determines combat range (long or short) with the smaller fleet gaining a bonus to their die roll. The defender places the ships down one at a time, and the attacker places a ship down to match. At the end, any left-over ships can be assigned to also fire on enemy vessels, or kept out of combat. The missile or beam factors of the firing ships are compared to the screen factors of the defenders, and a die roll determines if a ship has been destroyed.  Several combat options are available, including firing all of a ship's missiles at once, or the so-called "suicide attack" where a ship maneuvers to point-blank range for a beam attack.  Combat continues until one side is destroyed or until either player decides to disengage.

The game also includes abstracted rules for ground combat. Terran land units are green while Imperium units are black. In addition to regular land units and planetary defense units that can oppose a landing, there are special drop troops that can land on a planet without requiring a ship to transport them to the surface. If one side is all standard troops and the other side is all drop troops, the standard troops gain a bonus artillery attack against the drop troops to simulate the inability of the drop troops to carry a lot of heavy vehicles with them. The ground units have a single combat factor, plus a symbol and a unit identifier. Surface combat used a combat differential with the defense combat factor subtracted from the attacker's combat factor. A die is then rolled to determine whether the unit is destroyed.

The game system includes a random events table for various Imperium events. These can favor or hinder the Imperium player.  There is also a system built into the game for production of new units, colonization, and other changes during the inter-war periods. Ships can age and be scrapped; the Emperor can grant or withdraw permission to build certain ship types, and territory can be exchanged.