This is for RTS players, as I want to ask you about game mechanics ?️

I'm especially curious about those mechanics that you have found in only one or really a few of games, that you want to share. They can be good or bad ones, but must be rare ?️

I'll start with my list ?️:

Original War

The name of the game may be confounding as it doesn't means what most of the people think it means ?️. But title aside, the story of the game goes like that (shortly): in the Russia someone discovers a new mineral that makes producing high amount of energy very cheap. On the other side of the pond, USA founds an alien artifact that makes time travel possible. They make a cunning plan to steal the mineral from Russians during the latest Ice Age when transporting it from Siberia to Alaska is possible. So they send their troops using the alien artifact. Of course, Russians (in the alternate timeline) don't take that lightly and send their troops too...

The mechanics I want to describe here is based of an idea of scarcity: the troops depend on resources send from the future, because they can't make them on their own in 2,000,000 BC.

First such a resource are Crates: you need them to build anything. During game-play they appear on a map. There is one 'but" thou: the time machine used by both sides is imperfect and sends things to a random point in time and space. This means these crates appear in random places at irregular time moments. This forces players to leave their bases and "hunt" for crates. And the amount of these is also not big: one pack contains no more than 5 of them. And to make things harder at the beginning you can move only one crate at a time. This means you have to count every crate you spend and if you want more, you have to be more smart than your opponent and "sweep" away crates before he does.

The second resource are People: to put it simply, there is no building in OW that "produces" people. You are given a limited amount of humans at the beginning of each mission (usually 4-6 of them) with no way to replenish them (except a scripted event). And of course people are needed everywhere too: buildings doesn't work without them. So are tanks. This makes you do extra care for any of person you have and every death is a big thing here.

Both of these restrictions I've described above means there are no big bases and armies of thousands tanks in OW.

Earth 2150

The story of the game is: the orbit of the Earth has been destabilized and in a few months the planet will be destroyed. It forces three countries to build an escape fleet, but the last remaining resources on Earth are enough only for one side...

The mechanic in this game I want to show is: you play the game on more than one map at a time. In the vanilla game there are two of them, but the next add-on The Moon Projects adds another ones. One of these maps changes from mission to mission (and thus is called, no surprise here, "the mission map"). On the other side the rest of the maps contains your main base and these doesn't change. And there is a special unit, a transporter, that is used to move your units between maps. All it needs is a landing pad placed on a map.

This allows players to use an interesting tactics: all of walkthroughs made by players for other players advice them not to build anything on the mission map, except the mentioned landing pad. Every unit a player needs should be made in the main base and transported to a mission via the transporter.

This also means you can transport your units back from a mission and use them in the next missions. The same stands for technologies. So, this game avoids reinventing the wheel by players, because they don't have to make their armies from scratch every mission. It also creates another "problem": at some point you will have to decide if you send an old, but experienced unit with old weapon type, or a fresh new with the newest weapon, but being a greenhorn to a battle.

Earth 2160

A continuation of the above game. It doesn't contain the mechanics of the predecessor, but adds another one for one extra side: Aliens.

The aliens to the opposite to the human sides uses the base-less idea of playing: you don't build anything with aliens. Instead, every unit in this side is a resource gathering unit (besides the main propose of the unit). If one stands next to a resource point it "eats" it. When it collects enough of it, you can order it to clone or evolve. Cloning means you will get one more unit, while evolving...well, think here about Pokémons ?️. This means that even one unit, if it survives a battle, can re-make an army. And this makes that one side hard to defeat.

Homeworld

You can probably guess what mechanics I'm about to tell but I'll try anyway ?️.

It is the full 3D environment and also the feature-less scenery of the outer space. The first means you can attack your opponent from any side, and the second, you can't hide behind a bush for an extra defense.

But there is also yet another mechanics, similar to the one I described in "Earth 2150": your Mothership can move all your resources (which I mean both raw materials and your units) from mission to mission. This was used in the design of some of missions where you had to rely on what you were able to make/gather in the previous missions. If you didn't do well one mission, it meant your next mission will be harder if out impossible to finish.

Achron

3 words: REAL Time Travel.

Probably this is the only game not only among RTS games but games at all with such mechanics.

My take:

Total Annihilation / Supreme Commander

1. There are two resources: metal ("mass") and electricity. The first interesting mechanic is that you do not pay an upfront cost to make anything; you gradually spend your resources to make units and buildings.
   1. You can store a very limited amount of resources “in the bank”, so the game kinda expects you to constantly balance your spending and gathering. If you gather more than you spend, then you are not investing resources, and after your storage is filled, you will just lose these resources. If you spend more than you gather, then you have dead resources invested into production building which cannot produce due to the deficit; or, at worst, you destabilize your shields, your radars are down and you are in trouble (this stuff needs power in your sockets).
   2. Also, your build speed is limited by the number of workers you have, and the flow of the resources. There is no typical “build time”.
2. These games have no supply cap. That sounds cool and exists in a few games. This mechanic alone does not guerantee patented "Jumbo Scale Battles” these games are famous for (where whole map, which is 50X50km, is covered with things that shoot or produce the former). You see, mechanic above allows EXPONENTIAL income scale without any degenerate strategies or general jank (again, you cannot save resources - it cuts this stuff off). In the beginning, you get 2 metal/second; after 15 minutes you get around 60 metal / second; reaching end-game, players sometimes get 1000 metal per second - i.e. 500-fold increase since the start, which enables you to build 500X larger units - or 500X more regular units per second, which is a viable strategy as well. (**)
3. How do you scale your economy? You capture territory (special places that produce resources, then upgrade it). What if all such points are already taken? You attack expansions of your enemy, and capture then. If you haven't played these games, you might get an expectation that this need for aggressive map control coupled with constant resource gains means that units are constantly produced at factories and immediately march to the front line, where they die in a conveyor-belt fashion. The strategy of keeping your opponent on his toes using a constant flux of units looks like “selecting all units and pointing to enemy base”, not very strategy-ish. huh? Developers thought so, and they added the third pillar: reclaim mechanic.
   1. Every unit that dies leaves a small wreck behind. It can be recycled by any worker, putting some of the unit's cost in the bank. It means that you should not attack unless you are sure that you can win territory - or at least do more damage than your fallen units will give to the enemy. So, there are no constant marches of units. Instead, there are constant repositions of army forces, as you and your enemy anticipate possible angles of attack and look for openings to deal damage to the production or eco, and swift, surgical attacks.
   2. If you miscalculate, and your attack collapses away from your base - well, expect to meet this metal again, when the enemy converts it into his units and strikes you. (yeah, it's also a comeback mechanic - if the enemy survives by the skin of his teeth, he will have plenty of resources to rebuild with)

(**) - SupCom is an old game; it wasn't played much when it was released, but gained popularity over last decades. guess why? you were required to have a supercomputer to run it back then; and it's not bad programming. It's just pure scale of simulation, which modern PCs handle well.

Wow, I haven't thought much about economy design in these games, but now I see how a few unique mechanics support each other to provide a special experience SupCom is known for. I hope I conveyed my train of thought well. Thanks for the good question!

(probably, I should start writing full-fledged articles! : )

Fate of the dragon, move between local battle map of fortresses to world map, capture resources around while moving to attack enemy fortresses, units could be flown across walls with hangliders and by ladders, you could station all your troops ontop of the walls in a varied combination to prevent scaling and to utilize your archers.

Project Airos| War Inc, multiplayer was only a preconfigured map with a set amount of units of specific configuration, single player on the other hand, you had stock trading, each ‘field’ the company was in, if you owned majority stakes in it would net you additional benefits towards a specific unit class etc.
between missions, research allowing you to unlock new vehicles or troops which were better in different ways, you unlocked modules so that you could customize your vehicles for a very specific set of purpose and you could create multiple variants of the same vehicle.
while playing a mission, you had multiple tasks to destroy, you would typically start in your ‘home’ map, and you could leave for the ‘world map', and attack your primary, secondary and tetiary targets, you could bring specific units to build and farm bases in the mission enemies bases.

the AI bases would launch attacks on you, or intercept your forces while moving between targets, you could prevent this by having units sent early to prevent the enemy from sending task forces, time progresses in all bases even if you are there or not except when fighting with hostile attack force on the world map.
the game itself was quite easy, but had alot of interesting things that I haven't seen in any RTS game since.

American Conquest, honestly, I've yet to see a game to this day allowing so many players to have as many units fielded as American Conquest could, included things like friendly fire for your troops and cannons and fortresses, fighting against easy-medium indian tribes were considerably harder than most AIs due to the sheer amount of low tier units they would spam.