Balance in Zero-K should always be approached holistically, in respect to its design. It is a complex network of niches, counter mechanics and roles. These can be unit-unit counters, or situational dynamics such as terrain. When approaching units balance, determine first that you understand what a unit is meant to:
- Be good at
- Be bad at
- Be beaten by
And how it is meant to be used. Change a unit to stay within its role. Sometimes, it is the role which is too broad, and a new weakness needs to be introduced. A narrow role is better than a broad one, as long as a unit is very good at what it does. Always make sure units do not overlap identically in role, otherwise one or the other will always be preferable. More than balance, be conscious of how a unit makes the game actually play. Modifying a unit stats can totally change how the game plays, and even if something seems UP or OP, changing it would make the game play worse.
<CarRepairer> it's simple really. unit cost = (pwn - fail) * baw
Once you are sure you understand a unit's role, there are three areas you should test and gather information in.
This is the most important. If a unit cannot be used effectively in game, then it isn't OP (yet) and if everyone uses it then it isn't UP (yet). However, beware the culture of balance. Often a unit will go for weeks without anyone using it, and then someone discovers and exploits it. Soon everyone is using it, and it goes from being 'useless' to being OP. Be careful not to repeatedly buff an unpopular unit, it can take a long time before people come back to an unpopular unit and give it another shot. Don't be too hasty to nerf a popular unit- perhaps this is a 'fad', perhaps someone will find a counter. If you do nerf it, be conservative- don't try and over-nerf it just to ensure people stop using it because then its useless and will get buffed again.
Balance based on what good players do. This does not mean that you should balance the game entirely around the high-micro, hard to use 'pro' units or balance so that the game is only viable at a high level. However, good or inventive players can totally change the face of the way the game is played by effectively exploiting an underused unit. There are many units which an average player will not understand the use for until they have seen it used well.
Don't balance based on one game. Consult other players on their experiences too. You should test exhaustively, on several maps, with varying skill levels between the players. It is useful if testing a strategy to try it out vs someone, then get them to try it out vs you, both trying to counter.
1v1 is the most pure testing ground for a strategy. Team games often have different requirements but the various factors in play in team games make it very hard to get an impartial judgement, there are too many stray variables.
A good way to get impartial data on the use of units is through real game statistics. Statistical abnormalities are excellent candidates for trying to exploit ingame. Remember however that what causes the most cost in damage in a game isn't necessarily what decided the outcome- It might just be the mop-up crew, the victory may be economic, and a units effectiveness depends entirely on the skill of player using it. Keep Lancaster's square law in mind, masses of even a bad unit will be cost effective vs small numbers of a good unit.
Do for-cost tests of units. /spectator /godmode is your friend here! Micro both sides in various circumstances. This can help to nullify a whole range of factors that may be skewing your assessment, like economic differences and terrain. Note however that those factors are often precisely why those units are op, and that you wont really know how a unit works out ingame unless you use it in real situations.
Maths and Stats
Look at the actual stats of a unit. Compare it to similiar units. Sometimes one unit will appear to be OP when another one is actually far better. This is an incredibly useful tool in determining where the problem in a unit might lay, as often the problem will stand out immediately. Other times, it is something very subtle. Remember there are a huge range of values besides hp/dps. Range, speed, manoeuvrability, and even variables in the script like turret turnrate.
Think about everything in terms of cost. Knowing how much damage or HP something has is an abstract figure, what is important is its cost/damage cost/hp. Weight class (IE the cost, irrespective of cost-effectiveness) can also be very important, as a large unit has full DPS until it dies, while a mass of units of the same cost loses DPS as they die.
The use of a unit is not always determined by good stats, but often by the right combination and values. There is a huge difference between just out-ranging an LLT, and having the same range as an LLT. Try to think more in terms of unit relationships than pure numbers. When balancing a unit, try and think of other areas that can be changed to make it useful, rather than just its hp/dps. What specifically is holding it back/making it too strong ingame? Also remember knock-on effects. If you nerf something, another unit which it has until now effectively countered may suddenly be OP.
Be aware of what your values mean in relation to other units. Buffing a units HP by 5% might not actually do anything, because all the weapons that can shoot it still take just as many shots to kill it, or it might put it over a threshold which means it takes an extra shot to kill, for much more than a 5% difference. This matters particularly for Air vs AA, Subs vs Anti-sub, Missile Towers vs Raiders, and low RoF units like Penetrators, Skuttles and Spies.
Keep Quant's rule in mind, buff strengths, nerf weaknesses, otherwise all units tend over time towards the average and unit difference is lost. Ultimately though how it fits within the game design and how it can better fulfill its role is the most important factor though, and one of its strengths or weaknesses may in fact be preventing it from fulfilling that role.