Basics

This is a generic set of rules for miniatures combat for Mecha and other Robot and tech battle toys. Movement value and Weapon ranges are in units. This could be in inches, centimeters or whatever scale works best for the models and gaming area you are using.  I've used these rules almost exclusively for ZOIDS, but they should  work well for other toy lines or even a mix. The idea is to give a semblance of balance and fair play to your combat. But these rules are by no means perfectly balanced for every extreme of toy type and weapons fit.  The idea is to have fun, not min/max you way to a sure victory.
 

All battle units consist of a combat chassis, and weapon systems. The chassis could be anything from a mecha model, or a G.I. Joe, to your own construction in LEGOs.  I usually set my scale to the most common type of model I have, and classify this as a type 3 chassis.  And I use the class 0 for small vehicles  or individual soldiers in the case of mecha, or spy drones in the case of larger scale models. It's up to you to set the scale, but try and be consistent with all of all your models  and place them in different classes based on size. Toys with modular weapon fits work best, as you can customize and tweak your models to  hit a target cost.
 

There are 2 basic types of weapons systems,  Ranged weapons and Melee weapons. With some variations on both, and some that are in between. Each class of weapon has an associated  die that is rolled  when the weapon is used. The same size die is used for ranged and melee weapons of the same class. The larger the weapon, the greater the damage it can do,  and the larger the cost and drain and the combat chassis.  The weapons also have an associated armor  value and hits, these well discussed further in the COMBAT section. All weapons should be modeled and should be a good  match to those stated.

Ranged Weapons
Standard ranged weapons are line of site, and the models weapon should be pointing approximately at the target when firing.  For ranged attacks, rolls the weapons die. Apply this value, minus the targets armor, shields and cover.  The remaining value is marked off from the targets total hits. The armor value is  normally the same as the chassis class. Shields are a special case, see above.   Cover can be in different forms, and should cover at least 1/2 of the model.  It is also possible to target specific systems on a model. All of the modifiers are listed below, and are culmative.
 

Modified Range Weapons
In addition to the standard weapons in a class, you can also purchase reduced range weapons and increased range weapons, as well as bombs, rockets, grenades and indirect fire guns. Reduced range weapons are 25% cheaper to purchase then the standard version of the same class. They have half the total range of the standard version, and are half movement modifier penalty as well.  They are also treated as 1 class smaller for Close Combat. Increased range weapons are 50% higher cost  to purchase then the standard version of the same class.  They are identical to the standard  version weapon, except that they can fire at the same distance as a next class higher weapon.

Indirect Fire Weapons
Indirect fire weapons do not need direct line of site, and may be fired around obstacles.  You must be able to see part of the target, or have a forward observer that can direct your fire.  These weapons include artillery, rockets, and grenades. Indirect fire weapons  have some added inaccuracy by their nature.  All die rolls for indirect fire weapons are reduced by 1 for every 12 inches of range. I.E. a weapon fired at a target 37 away would be at a -3 to it's die roll. This is in addition to any modifiers for cover and terrain. Treat completely blocked direct line of site as hard cover.

Bombs, Grenades and Rockets
Bombs are either dropped from flying models, or left as mines on land or water. And can be remote detonated at any time. Grenades are the same cost as bombs and can be luanched up to 12 units away from attacker. Rockets are 2x the cost of bombs, but can be fired to full weapon class range. The main advantages of these weapons is that they can all be fired at once, and they have a reduced effect on movement.

Some ranged weapons can also be used in close combat along with Melee weapons. To use ranged weapons in Close Combat, the weapon must be a lower class value then the chassis of both opponents.
 

Melee Weapons
Melee weapons  are used in Close Combat, and can be incorporated directly in to the chassis, such as a fist or tail, or they can be hand held or drawn. These typically have no use outside of close combat, but can very effective when used.  Melee weapons are usually an upgraded component that is normally part of the chassis, and are therefor less expensive then ranged weapons and  less drain on the system for speed and power.

Also, Melee  attacks go directly against the target, ignoring armor and terrain, being countered only by other CC weapons and shields. Close combat is also very dangerous, where both the attacker and defender can end up taking damage in a round!
 

All combat chassis (model or action figure) have a basic movement value of 15. This value can be increased using boosters, or reduced by a combat  load (weapons). The standard unit travels on the ground, either by rolling on wheels, walking,  hovering or other  technology. In addition some units can fly, swim or tunnel, and have appropriate modifiers and limitations.
 

Combat consists of rounds. In each round opponents simutainiusly give orders and fight. At the beginning of a round all units (individual models or formations) are given orders. These are in the form of order tokens. Once all units have received an order token, they are revealed, and combat commences. Combat orders are played out in the following sequence.

Stand and Fire    -    Red token
 Unit maintain their position.  It may rotate up to 90 degrees, and fire all ranged weapons.  If attacked in close combat, unit may fire CC weapons before melee begins (close range attack), or use them in melee. This order is not available for a unit that is currently in close combat or in flight.

Retreat    -    White token
 Unit may move at twice normal rate.    They may rotate up to 180 degrees and may not fire weapons initiate close combat.

Charge    -    Green token
 Unit may move at twice normal rate.  It may rotate 2 times up to 90 degrees and  if in contact with an enemy unit must stop movement and commence a round of close combat. If the enemy unit is distorted or immobilized, the charging unit may finish its movement and attack again. Units may not fire any weapons other then close combat.  Unit may fire CC weapons in one melee only. This order is not available for a unit that is currently in close combat or  dug in.

Attack    -    Yellow token
 Unit may move then fire, or fire then move.  They may rotate 4 times up to 90 degrees at a time and fire all ranged weapons. This order does not apply for a unit that is currently in close combat.
 

Resolve all battle for each order type, including allotting damage and it's consequences to movement and attacks, before going to the next order. If two units have the same order, play them in the order of smallest to largest, based on chassis class and then overall cost per model.

For ranged attacks, rolls the weapons die. Apply this value, minus the targets armor, shields and cover.  The remaining value is marked off from the targets total hits.  Unless a specific component is targeted, the target model can designate damage location, see sample chart below.

For close combat, resolve any close ranged weapons fire. Resolve these as regular ranged combat, using armor and shields, but ignore terrain and cover.  Allot damage and it's consequences to movement and attacks, before starting melee attacks. Note, any  weapons fired in close range attack can not also be used in melee.  When  attacking a formation, or being attacked by a formation, all attacks are resolved at the same time. In other words all dice are rolled at the same time by the opponents, and treated as one model attacking another.

Melee attacks go directly against the target, ignoring armor and terrain, being countered only by other CC weapons and shields. Close combat is  dangerous, it's possible for both opposing models to be damaged or destroyed in a single round of combat!

Melee use the same die as ranged weapons of the same class. Roll all your dice at once, including any remaining close ranged weapons. You opponent does the same. Match up die, highest roll against you opponents highest roll, subtract the value of the smaller from the larger. The remainder goes directly to the smaller valued die owner. The model receiving dame can allot the the damage where he wishes. Now match up the next highest to your opponents next highest die, and continue the same process.

Any remaining die that are unopposed go directly as damage to the opponent, and can be allotted by the owner of the die!