Combat in Sunrider is fought out in turns and each unit is primarily limited in what actions it can take during a turn by the amount of energy it has available (EN). You also have to take into account difficulty settings and objectives. No matter the latter though, every battle will always end when there is no enemy unit on the map.
Battles take place in a 2-dimensial battle grid of 16 by 18 cells. Positioning is vital as defenses such as shields and flak extend to friendly ships near them (how near depends on the flak and shield range). Often the player will need to make difficult choices between moving a ship to cover others, retreat into cover or using powerful abilities.
In addition to commanding each individual unit the player also has access to special orders that can turn the battle when used, but require valuable command points, which are earned by performing well in battle.
The combat as done directly in the map. You have to take into account the type of weapon, its accuracy and the enemies stats between other things. Collocation to ensure that you have some defense against the enemy is also vital.
The selection of the difficulty directly impacts the combat, but it also has some other consequences, such as a reduced or increased number of CP upon victory.
Buffs are special abilities, especially from support units, that either enhance or reduce your (or your enemies) capabilities. The most common buffs are the damage and accuracy ones, such as the ones you get from Full Forward. There are more particular ones, such as Stealth or Awaken, which are more like singular abilities than buffs but share their characteristics.
The most important characteristic of buffs and de-buffs in that they are not stackable: debuffs will always overwrite buffs, and viceversa. This means that if an enemy casts "Flak Off" while you have "All Guard" activated, you will have 0 Flak, and not 10 Flak left. Conversely, if you use All Guard after the enemy has cursed you, you will recover your flak and get the +10 bonus. A wise use of this can easily change the tides of many battles.
Positive buffs are also not stackable between them (you can't cast Aim Up 2 times to get a 40% increase on hit chance), but the newest doesn't overwrite the oldest if that oldest is the stronger one. This means that you can use Full Forward without worries of losing Sola's Awaken mode, but you'll have to take into account that once Awaken's buff ends, Sola won't have any of the buffs of Full Forward.
Depending on your skill and experience, you may be able to use some especial command skills only accessible to the best (or most resourceful) commanders. These are the orders, and may enquire something so simple as a general buff to all units, or something like firing the Vanguard cannon. They are wholly separate from the other commands and don't require any EN nor unit, and can be activated any moment of your turn, but require Command Points, commonly known as CP.
The enemy units tend to follow standard patterns, normally attacking your units based on the damage they can deal (taking into account the accuracy too of course) and the potential damage your units can do to them. However, PACT soldiers are not unfeeling machines, and so they remember clearly which unit has been the one that has caused most casualties to them in that battle. Every one of your units gets a certain amount of "hate" based on the damage they deal, and get an extra amount when they finish an enemy unit. Logically, the bigger and stronger the enemy unit is, the more "hate" the unit that finishes it will receive.