View source for "Guts of the Battle Engine" by James McGuigan - 23 Jan 2002

{{old|Guts of the Battle Engine}}
This article was taken from (non-article database) [http://www.starsfaq.com/battleengine.htm content] at [[Stars! FAQ]]
* Author: James McGuigan
* Written: 23 Jan 2002

Here are the guts of the battle engine as I understand it from both experience, observation and the help file (please pull me up on any points I get wrong)

For a battle to take place 2 or more fleets (or a fleet and a starbase) must be at the same location and at least one of the fleets must be armed and have orders to attack ships of the others race (the type of ships involved doesn't matter). If are race has a fleet present at a location where there is a battle, but doesn't have orders to attack any of the other races there and none of the other races present has orders to attack it then it will not take part in the battle (and can not benefit from potential tech gain).

Each ship present at the battle will form part of a token (AKA a stack), it is possible to have a token comprised of just a single ship. Tokens are always of ships of the same design. Each ship design in each fleet will create a token, splitting a few ships off to form a second fleet before the battle will create a second token on the battle board.

The battle grid is made up of 10 squares by 10 squares. Each token is in a single square, there can be more than one token in the same square.There is an limit of 256 tokens per battle event for all players involved, if this limit is exceeded, then excess tokens will be left out (those created from fleets with the highest fleet numbers), in such a case each player will have an equal number of tokens, each player will be guaranteed to get their "share" of the available token slots (ie in a 4 race battle 256 / 4 = 64 token slots), if a race doesn't use up all their "slots" then they are shared equally between the other players.

Each battle is made up of rounds. There are a maximum of 16 rounds in each battle. Each round has two parts, movement and shooting. Each token has a speed rating, and will be able to move between 0 and 3 squares in a single turn. If a token has a fractional speed rating then they will get a bonus square of movement every set number of turns. a 1/4 bonus means an extra square of movement on the first round and then on every fourth round after that starting with the fifth. A 1/2 speed bonus gets a bonus square of movement every other turn starting with the first, and a 3/4 speed bonus gets a bonus square of movement for the first three rounds of every 4 round cycle. The order of movement is this, each token with 3 movement squares moves a single square, then each token with 2+ movement moves a single square (if it had speed 3 then it would move for its second square) and then all ships with at least one square of movement move again. At each stage the ships with the most weight will move first though there is less than a 20% difference in weight then there is a chance that the lighter ship will go first. The smaller the weight % difference the greater the chance of the lighter ship going first.

Each token has an attractiveness rating. This is used in both working out where ships move to and which ships are shot at first. The essence of the formula is cost / defence. A ship will have different attractiveness ratings verses different types of weapons (beams, sappers, torpedoes and capital missiles). Cost is calculated by summing the resource and boranium costs of the ship design used (iron and germ costs don't affect the attractiveness rating). Defence is calculated by the shield and armour dp modified by the enemies torpedo accuracy (after base accuracy, comps and jammers are worked out) if defending vs torps or capital missiles, the effects of double damage for unshielded targets vs capital missiles and the effects of deflectors against beam weapons. The attractiveness rating can be change during the course of the battle as shields and armour deplete. Attractiveness doesn't take into account the one missile one kill rule, thus chaff has become a fairly effective tactic.

Battle orders are comprised of 4 parts. A primary and secondary target type, legitimate races to attack and the tactic to use in battle. Ships will only attack tokens belonging to legitimate target races, however if another race present has any ships (including unarmed ships) with battles orders to attack your race then that race will also be considered a legitimate target. When attacking ships will try and shoot the most attractive ship of a type listed as a primary target and if no ships are available which are primary targets then the most attractive ship of a type listed as a secondary target will be targeted. Ships which are not listed as primary or secondary targets will not get shot at, even if they are shooting back.

There are 6 different battle orders which determine the movement AI of the ships in battle, the movement AI is applied each time a ship wants to move a square on the battle board.:

Disengage - If there is any enemy ship in firing range then move to any square further away than your current square. If you are in range of an enemy weapon but cannot move further away then try move to a square that is of the same distance away. If you are in range of the enemies weapons and cannot move away or maintain distance then move to a random square. If you are not in range of the enemies weapons then move randomly. Also you will try and disengage which will require 7 squares of movement to be clocked up before you can leave from the battle board.

;Disengage if Challenged:Behaves like Maximise Damage until token takes damage and then behaves like Disengage.

;Minimise Damage to Self: (Not 100% sure on this one) If within range of an enemy weapon then move away from the enemy (just like Disengage). If out of range of the enemies weapons or cannot move away from the enemy then try and get in range of the best available target without moving towards the enemy.

;Maximise Net Damage: Locate most attractive primary target (or secondary if no primary targets are left). If out of range with ANY weapon then move towards target. If in range with all weapons them move as to maximise damage_done/damage_taken. The effect of this is if your weapons are longer range then try to stay at maximum range. If your weapons range is the same then do random movement while staying in range. If your weapons are shorter range and also beam weapons then attempt to close in to zero range.

;Maximise Damage Ratio: As Maximise Net Damage but only considers the longest range weapon.

;Maximise Damage: Locate most attractive primary target (or secondary if no primary targets are left). If any of your weapons are out of range of that token then keep moving to squares that are closer to it until in range with all weapons. If using any beam weapons (as they have range dissipation) then attempt to close to 0 range. If just using missiles or torps and in range then move randomly to a squares still in range.

Note that there is a bug when fighting starbases, the battle AI doesn't count the +1 range bonus when calculating movement. This mainly applies when your ships are attempting to get out of range of the enemy, so vs starbase with range 6 missiles, your ships will move to distance 7, the movement AI won't calculate that they are still in range even when they keep getting shot at.

After the movement phase all ships will shoot their weapons, a token will fire all weapons from the same slot in a single shot. The weapon slot with the highest initiative will fire first. If there are two ships with slots of the same init, then the ships will be randomly given a priority over who can fire first (which will stick for the entire battle). The rest of the weapon slots are then fired in init order. Damage is worked out in between each shot and applied to the ships. If ships or tokens are destroyed before their turn to shoot then they won't be able to fire back. The movement AI will go after the most attractive primary target on the board, but if this token is not in range, then the ship will fire on the most attractive primary target within range (or secondary if none available). Starbases have a +1 range bonus to all their weapons (this also gets applied to minefield sweeping rates), though cannot move. The movement AI doesn't take this bonus into account when moving ships to close in on an enemy starbase.

Damage for each shot is calculated by multiplying the number of weapons in the slot by the number of ships in the token by the amount of dp the weapon does. For beam weapons, this damage will dissipate by 10% over the range of the beam (for a range 2 beam - no dissipation at range 0, 5% dissipation at range 1 and 10% dissipation at range 2). Also capacitors and deflectors will modify the damage actually done to the enemy ship. Damage will be applied first to the tokens shield stack and then to armour only when the entire shield stack of the token is down. For missile ships, each missile fired will be tested to see if it will hit, the chance to hit is based on the base accuracy, the computers on the ship and the enemy jammers. Missiles that miss will do 1/8 of their damage to the shields and won't affect armour. For missiles that hit, upto half will be taken by the shields, the rest will go to the armour. For capital missiles any damage done after the shields are taken down will do double damage to the armour. Whole ship kills are worked out by adding up all the damage done to the armour by a single salvo (from a token's slot) and dividing this by the amount of armour each single ship in the token has left (total armour x token damage %). The number of complete ships the shot could kill will be removed from the enemy token, the rest of the damage will divided equally among the rest of the ships in the token and applied as damage. As token armour is stored in 1/512ths (about 0.2%s) of total armour and not as an exact dp figure (shields are stored as an exact figure), there may be some rounding of the damage after each salvo (AFAIK its always rounds up). This fact can be abused by creating lots of small fleet tokens with weak missiles and many slots, where each slot that hits will do 0.2% damage to the enemy token even if each individual missile would do less damage normally (especially the case with a beta torp shooting a large nub stack).

After all the weapons that are in range have fired, the next round begins, starting with ship movement.

The battle is ended when either the 16 round timer runs out, there is only one race left present on the battle board or if there are two or more races which have no hostile intentions towards each other.

After a battle, salvage is created. This is equal to 1/3 of the current mineral costs of all the ships that where destroyed during the battle. This is left at the location of the battle and will decay over time, or if the battle happened over a planet, then the minerals will get deposited there.

Any races that took part in a battle and had at least one ship that managed to survive (either through surviving till the end or retreating beforehand) has a potential to gain tech levels from ships that where destroyed during the battle. For the exact details of the formulas and chances involved see the [[Guts of Tech Trading]].
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