Ability Management and the Human Revolution

For the Uninitiated...
      Deus Ex: Human Revolution is a prequel to the critically acclaimed Deus Ex released back in 2000. It follows the story of Adam Jensen, the chief of security for Sarif Industries, a massive corporation on the cutting edge of human augmentation (aka making cyborgs). Following a particularly gruesome brush with death, Adam is revived thanks to cybernetic "augmentation" technology, making him better, faster, stronger... with a few extra toys the 6 Million Dollar Man could only dream of.

      This is all set to a backdrop of intrigue and conspiracy, staples of the series, centering largely on the ethical quandary of whether human augmentation (ie slicing off limbs to replace them with robotic parts, enhancing the brain, etc) should be regulated.

      The game plays like your typical sci-fi first person shooter, with a heavy emphasis on stealth and using your augmentations to get an edge on your foes. It is well executed and blends its RPG elements well into the action.

      But forget all of that, lets talk ability management.

Always pack a few Energy Bars!
      Of all the things to stand out about DX: HR's mechanics, I found its energy system the most unusual.

      In DX:HR, you have a set of energy cells below your health bar, between 1 and 5 depending on upgrades. Abilities will either deplete your energy slowly, or cost an entire cell. If you have a partially depleted cell, it will replenish over time, but if you use up a full cell, it can only be restored by using items.

      At first I found this system odd, and took a little while to get used to, but after thinking about it for a little bit, I realized this is actually a very elegant piece of design.

      This kind of ability management system allowed for a player to manage their energy in interesting ways. Players could choose to use their cloaking or see-through-walls ability in short bursts to use them essentially for free, or blow through all their energy to stealthily clear out a room, but be tapped out afterward. It added a new dimension to the energy bar in a way that went beyond what I expected, adding nuance without being overly complex.

Going Deeper
      Looking at DX:HR's energy system inspired me to look at how other games deal with ability management, and how those design choices impact the player's experience. Regardless of whether they use mana, energy, or some other sort of resource, there are a few paradigms that show up frequently across the many games I've played.

• Traditional Mana Pool A system where a player has a resource that is sufficient to allow players to use abilities fairly frequently, but eventually cuts them off or forces them to invest in mana potions or take a break before being at full capacity. This system rewards a player that uses their abilities occasionally, while punishing a less frugal player. Almost every Final Fantasy (I through X) uses a system like this.

• Precious Resource An ability management system where every ability used diminishes a resource that is not easy to replenish, or takes a long time to replenish. This forces players to consider each ability used carefully, forcing players to be strategic and think ahead and decide whether to use an ability during a particular engagement, or save it for later. The energy system of caster units in Starcraft 2 are great examples of this.

• Clutch Similar to precious resource, but usually only applies to a few specific abilities granted to the player. Generally these are the once or twice per encounter abilities (such as Biotic Powers in Mass Effect) or once per day powers (such as the racial powers in Skyrim). They are usually very powerful abilities that can turn the tide of battle, but can just as easily be wasted. They rely not only on timing and forethought, but also skill in accessing an encounter and determining if it warrants using such an ability.

• Burst Where you are able to use abilities in rapid succession, but with a period of downtime afterward. The clearest example of this comes from the energy-based champions of League of Legends, such as Kennen, Akali, or Shen (shown below). Similar to clutch, this kind of system also emphasizes timing, but also allows a player to go all-in with everything without as much downtime as in a Diminishing resource system.

Consequences and Tradeoffs
      Each ability system has its benefits and tradeoffs, which much be taken into consideration when it comes to game balance. It is easiest to compare these systems side-by-side in a game like League of Legends, which features a huge variety of different ability management schemes for each of its 50+ champions.

The Real Cost of Mana
      Champions that use a Traditional Mana Pool are generally the ones with the most powerful abilities right out of the gate. The main drawback for them is that eventually they have to return back to the nexus to replenish their mana more often than other characters. This leads to more downtime, and forces them to invest in mana replenishing items or items that boost their maximum mana, which can hold back their damage potential.

      On the other hand, by late-game they can end up having so much mana that mana use becomes a non-issue, as they can spam their abilities with impunity. While it isn't a huge deal in the session-based play of League of Legends, it can be a problem with single-player games, as by the end of the game a player may well have the ability to use their abilities with impunity. Most RPGs compensate for this by having higher-level spells cost more, however, but that isn't always enough. (see my Knights of the Old Republic example below)

Not Enough Mana!
      Traditional Mana Pool and Precious Resource systems can also fall prey to attrition, where the player doesn't have enough of the resource they need to do anything. Generally this is not a huge deal in League of Legends, but I can recall a time when playing Final Fantasy VII when I neglected to buy enough ethers (which can't be bought in most places) and thus ran out of MP before being able to kill the final boss. In these kind of situations this can lead to tremendous frustration for players, hence why more modern versions of these systems usually have some system of passive regeneration of these resources, or some other means of replenishing these that is always available.

The Sustain Pain Train
      Clutch and Burst-type champions have a significant advantage over Traditional Mana Pool champions, as they are able to remain in their lane longer, and don't have to waste money on replenishing or increasing their mana allowance. This translates into more money for better items, and the ability to remain in one's lane longer to farm gold and experience. To compensate for this advantage, burst-type champion's abilities usually do less damage than their Traditional Mana and Precious Resource counterparts, while Clutch abilities tend to have significantly long cooldowns.

      In other games, such as Mass Effect, this system works excellently in keeping a steady pace to the game and complements the more tactical decision making action games of its kind leverage. It frees players from having to worry about some mana pool running out or when to use a powerful ability so players can enjoy the thrill of the combat, rather than scratching their head while they draw out their battle plans.

Final Thoughts
      Ability management systems have a huge impact on how a player interacts with a game, and can help or hinder the overall feel of a particular game or playable character. When designing such systems, there are a number of things a designer should consider:

Self-Sufficiency vs Incentives
      If we think of ammunition in a First Person Shooter as a type of ability management system (which it is), then we can easily make sense of the old FPS convention of having health and ammo packs scattered around levels. This encouraged exploration by rewarding players for finding hidden rooms or other nooks and crannies in the level. Modern games put less of a reliance on going out of your way to find health and ammo, with most FPS adopting a fully regenerating health system akin to Halo and plenty of ammo dropped by fallen enemies, making nooks and crannies more of an optional venture for those that want a few extra grenades or rockets.

      But having a good system that rewards and encourages exploration for an exploration-based game can be a very important tool to keep games fresh. Skyrim, for example, has a system where a player must use soul stones to recharge their magical items after they have been used up (essentially a less annoying version of having to repair damaged equipment games like Fallout 3 have). This system is done in a way that is not intrusive or much of a hassle, while still making opening a chest only to find yet another common soul gem still be something useful to the player, and a subtle incentive to keep looking.

Avoid Mechanical Obsolescence
      If an ability management system is not balanced properly, then using an ability can go from being tactical to trivial later in the game. While it can add to a player's sense of growing power as their mana allowance grows, it can just as easily make the player feel nigh-invincible and strip any challenge out of the game.

I found Knights of the Old Republic 1 and 2 to be some of the most egregious offenders, as by the end of the game the sheer amount of Force Points at your disposal combined with no cooldowns on abilities made it possible to spam your most powerful spells to clear entire rooms of enemies in seconds and turn even the menacing boss into a joke.

I'm looking at you, Force Crush!

      Even if you are thinking in terms of a casual player who isn't looking for a lot of challenge, this still creates an upside-down difficulty curve. Early game the player would have to pay attention to their energy, health, etc and plan their actions accordingly, but by the end the only choice they have to make is whether to summon an ultra-demon to crush enemies slowly or kill them all outright with lightening bolts.

Put a New Twist on an Old Mechanic
      Innovations in ability management has gone a long way toward turning what started as a balancing mechanism into a fun component of the game in its own right. For example, in Skyrim, I have made a powerful mage character and equipped him with a Magicka-draining bow. Thus, whenever I run out of Magicka from casting spells, I can switch to my bow for a few shots until I'm back up to full again, then lay down the firey pain once again. While not the usual means of regaining magicka, it is nonetheless far more enjoyable that chugging a few mana potions and casting more spells.

      Tabletop roleplaying games have perhaps some of the most interesting takes on ability management, which go beyond a mana/energy resource. The Paradox system of Mage: The Ascension, for example, penalizes players for casting spells in front of mortals (on top of the cost to cast the spell normally). If they accumulate too many points in Paradox, some strange effect might occur, from a character's face turning into a black hole, a getting trapped in a repeating time loop, or becoming possessed by an evil spirit. Not only does this make the system more interesting but also reinforces the overall theme of the game.

Conclusions
      In short, ability management systems should be designed and looked at in terms of how they will impact player behavior, reinforce game pacing, and complement the atmosphere of the game's narrative.