Experiential unit design is the realm of making units and other game components feel different from each other, players have to think completely differently about Siege Tanks and Zerglings because of good experiential unit design. It may sound like a simple topic, but many RTS games have failed due to not executing it properly, resulting in a bland game where unit control is unsatisfying. Today I'll be exploring examples of superb experiential unit design from a few of my favorite RTS franchises, including Ashes of the Singularity: Escalation. 

Command and Conquer

In Command & Conquer games, players control a variety of units ranging from infantry, tanks, motor bikes and aircraft. These different unit types have large stat differences such as tanks being tough, infantry being cheap and aircraft being fast, but that's only part of the picture. It's important that units have unique properties to distinguish them in ways which are more interesting than just stat differences. For example, aircraft have limited ammunition and need to land on the airfield to be replenished, tanks can crush, and infantry can garrison neutral structures or be loaded up in transports. 

Experiential design can also be cosmetic, the Telsa Coil in Red Alert has nothing fun about it from a gameplay perspective, yet it's so cool because the weapon effect is totally unique to anything else in the game. (Until the introduction of Telsa Tanks & Tesla Troopers.) If it's not possible to make something unique through experiential gameplay design, giving it a unique style and effects can achieve a similar result.

StarCraft

StarCraft combines melee and ranged combat which creates a wide variance between the unit types. Due to the ranged/melee attacks and various properties of Marines and Zerglings, players have to think tactically about how and when to engage. Playing with Marines forces players to think about how to minimize surface area and forcing the enemy to engage in choke points. Siege Tanks and High Templars both provide powerful area of effect damage, but those units are used and thought about in incredibly different ways. Siege Tanks need to deploy in a stationary mode to fire, but High Templars have limited energy that is required to cast a spell. Units can perform similar roles but while being thought about in unique ways.

Company of Heroes

Company of Heroes is a much smaller scale RTS and consequently has many tactical mechanics that vary between infantry and vehicles. You need to interact with the battlefield in different ways depending on which units you're using, infantry position themselves behind directional cover for protection while tanks roll over cover. Roads should be avoided by infantry because it provides negative cover while vehicles receive a speed bonus. Other iconic Company of Heroes mechanics only apply to certain unit types which also helps make those units viscerally feel the way they are supposed to.

When Infantry receive machine gun fire they become suppressed which heavily reduces their movement and combat capabilities. Relic could have decided to have tanks also debuffed from all machine gun fire which buttons up the tank crew and limits their sight, but doing so would have ruined the emotive feelings associated with those unit types. Infantry are brought to life and made to feel vulnerable through the dynamic movement as they automatically weave in and out of cover then drop to a crawl when machine gun fire goes their way, meanwhile tanks feel destructive and tough as they crush everything in their path and have thick armor that negates all small caliber bullets. A tank wouldn't feel like a tank if you could destroy it with small arms fire.

Supreme Commander

Large scale RTS games make experiential design more difficult to implement because there's little focus on micro-management and abilities. Supreme Commander still manages to have some variance on gameplay mechanics design such as Cybran naval ships being able to traverse land, but the main way Supreme Commander makes units feel varied is by having large differences to the stats and creative art design. The UEF Fatboy could be viewed as an equivalent to the Seraphim Ythotha as they're both experimental ground units, but the Fatboy is very different. Not only can it produce units, it also has long range and splash damage compared to the powerful single target weapons.

Unlike the Fatboy, the Cybran Spiderbot has practically an identical role and weaponry to the Ythotha, so how does it still manage to feel unique? The Spiderbot, as the name suggests, resembles a Spider with its six legs giving it a different feeling of locomotion, albeit only at a cosmetic level. The Ythotha and Aeon Galactic Collosus are even more similar as they're both bipedal walkers, and yet they still manage to feel different from each other. The Galactic Collosus has a single deadly laser weapon that makes up almost all of its DPS, while the Ythotha has three separate weapons that each share roughly a third of the overall DPS. The Galactic Collosus also has Tractor Claws which sucks up nearby low tier units, and while the overall DPS of the Tractor Claws is largely insignificant, it looks cool and is a unique weapon which makes it feel different to use. 

Ashes of the Singularity: Escalation.

Experiential design is equally a challenge in Ashes of the Singularity: Escalation due to the large scale, and creating vastly different appearances can be expensive from a development perspective. One of the methods for implementing experiential unit design in Ashes is veterancy that only applies to high tier units, and in differing ways. Almost all RTS games that feature veterancy handle it in the same way for every unit type. In Ashes only the dreadnoughts and juggernauts (Tier 3 & 4) units have veterancy which makes them feel more important, separating them from the expendable low tier units.

The dreadnought upgrades achieved through veterancy are unique for each dreadnought type, which refines their role by providing them with new bonuses or weaponry. Juggernauts also have veterancy, but it's applied very differently. When juggernauts level up, they automatically receive a small stat bonus which can be applied infinitely; there's no limit to how many times juggernauts can level up which makes them feel more like ultimate late game tools. Unlike juggernauts, dreadnought upgrades can provide bonuses to an army lead by a dreadnought, which adds to their role of being designed to lead armies. 

Conclusion

Experiential unit design is one of the most crucial components of making an RTS game fun. Differences to stats and cosmetics is a crucial part of experiential variance, but a more interesting approach requires unique properties and mechanics. Players should think about different unit types in different ways, else an RTS game becomes bland with all the units blurred together.