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The essence of this question is basically this: consider a strategy, RTS or a tower defence game, where you have the choice to build a new unit or to upgrade an existing one. The upgraded unit is definitely worth more than a non-upgraded one, but by how much?

In designing a upgrade path, how do I design it such that

  1. Upgrading is worth the time and effort
  2. However, upgrading doesn't becomes too über that the player forgo building new units?

For example, in Defence Grid, a glance at a number shows that two Level 1 Gun turrets do less damage output than a Level 2 Gun turret; however there are advantages to having 2 towers over 1 (say, you need to cover two different paths).

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Testing. I think that's probably the only efficient way. – The Communist Duck May 22 '11 at 10:16
up vote 6 down vote accepted

In Sanctum (tower defence) you get the most damage for your money by building low level turrets. However, depending on how you build your maze not all turret positions will be equal, some will be able to shoot for long periods of time, others not so much, so the optimal strategy would be to build high level towers at the best points, low level towers at the lesser points, and nothing at the very worst points.

RTS games are quite different, the whole position aspect doesn't exist for mobile units. A typical formula is to make the high level units overall better for their price, but make it so that you have to do an initial investment in order to be able to build them, that could be do some research that takes time and cost money, or build a structure to enable the construction. So the player will have to balance when to move for the higher level units, which at that point will decrease the immediate unit output and thus temporarily weaken the player. Another thing to do is make the strengths of the units different rather than one just being stronger than another, they will have different perks making a strategy that combines them and is capable of adjusting depending on what the enemy does optimal. This is for instance very typical for Blizzard RTS games, but it takes a lot of skill, time and testing to do just right.

And finally an anecdote:
The optimal multiplayer strategy in the RTS game Earth 2150 is to choose the Lunar faction and build nothing but Lunars equipped with machine guns. This is basically the cheapest fighting capable unit in the game, whenever taking fire it's gone almost instantly. But it's cheap, and very quickly produced, so you can field an abundance before the opponent has a chance to do anything serious.

Not a lot of people ever discovered this on their own, everyone just presume that it's a worthless unit, because that is what a lot of other games and campaign mode has taught them.

Balancing is a really tough job, and it's very easy to fail in anticipating a simple winning strategy.

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It appears that you have BBQsauced the crap out of other answerers sir. – Olhovsky May 27 '11 at 20:19

You should consider the price and the time it takes to upgrade, if you have a fixed upgrade/build time for every unit you can ignore that.
The value(for the player) should scale with the price he pays for it.

You should also consider how much time it needs to gain a certain amount of money.

Just a few thoughts.

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Damage to the enemy from a tower is a combination of damage amount * field of fire area.

As a player, when deciding to either upgrade an existing tower or build a new tower, you would do a rough calc of field of fire area * damage strength * cost. For towers that have small field of fire area, it is usually better to build new elsewhere, but for well located towers with above average field of fire area, you would want to upgrade.

As a designer, create opportunities for both so your players will have to strategize about it or experiment with it or at least mentally engage himself in that concept. Create some borderline locations too to try to trip up the player a bit before they catch on.

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upgrading usualy doesn't consume space but building some new guns need more space so if I were to balance them i would put higher price for upgrades, and besides i think it's logical that upgrades take less time than new building, but that's for you to decide, so i think for an upgrade that duplicate a tower's power i would set 1.2 of the tower original price and 0.9 of it's building time. the same senario goes for rts games, except map size limit and it's usualy population limit that prevents you from building lots of things.

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Another thing not mentioned of course is rate of fire / recharge speed.

This can apply offensively or defensively (ie shields).

Falling back on the tower examples noted already, and just being quick and loose with costs (no analysis, just off the cuff) you could have more low level towers at fire power 1, rate of fire 1, range 1 for cost 3 or you can have an upgrade with fp 2, rof .75, range 1.25 for cost 4.

Now the scenario where more low level is better is the scenario where you have swarms of enemies. That 3/4 rate of fire might just require you to build more towers at more cost.

The high level becomes more effective as enemies requiring multiple hits start to appear, now you're getting 2 shots for the price of 1.

To turn this into a defence strategy think about varying hit points or shielding (tower defence where the enemies attempt to destroy your towers, not just bypass them?)

Hope this helps

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