Few video games have the ability to intimidate newcomers as much as turn-based tactical RPGs. Unlike other classic turn-based RPGs - such as Final Fantasy - the turn-based tactical strategy genre focuses on a completely different player niche, and thus the gameplay characteristics, styles and preferences are, as a whole, a huge puzzle for the player to solve with patience.
In these games, time stands still between two turns until the player executes an action, and therefore has more time to think. But, unlike classic RPGs where, in general, the player finds friendlier options, in a tactical strategy game a very different prism opens up, an extra dimension: the movement capacity of our units.
This can generate insecurities for many players. "Will this be a good move?", "how will the machine react afterwards?"... These are questions that, perhaps, we have all asked ourselves, and it is perfectly understandable. In a classic RPG we have a complete visual of the scenario where the battle takes place, because the enemy units, whether two, three or more, will always be in sight. On the other hand, in a turn-based tactical RPG, we usually have a visual limitation of the opponent, as some of their units may be behind the "fog of war" or simply appear by surprise when the battle has begun. This style of play generates a feeling of helplessness and lack of control, which for some, far from being fun, can be intimidating.
"In a tactical strategy game, a very different prism opens up, an extra dimension: the movement capability of our units."
But tactical role-playing games have virtues that transcend their genre. They are very stimulating experiences because they all have a differentiating element that, when well implemented, provides a highly entertaining gameplay experience: the AI; in other words, the way in which artificial intelligence responds to our actions.
During the development of a turn-based tactical RPG, the challenge is to create organic behavior patterns that react with natural intelligence to our tactics. The AI, in theory, must be able to perceive several parameters simultaneously. It is not enough that enemy units advance towards us and attack any unit within range, or simply that each unit fulfills its specific role. What is sought, in addition to the above, is for the AI to know how to analyze the scenario in search of a better position, to execute the best timely action within its possibilities and put the player on the ropes. The goal, without further ado, is to design an attack and defense strategy that looks like a natural, intelligent and thought-out reaction, providing a challenge for the player.
For this article, I enlisted the help of some veterans in the industry: the development team behind Lost Eidolons, one of the most fun tactical RPGs of the moment. Ocean Drive Studios, based in Korea and with an office in Los Angeles, have answered some questions about AI pattern design.
In tactical terms: What are the challenges of programming algorithms for AI?
Ocean Drive Studio: The challenge is to cover delicate tasks to maintain performance. In turn-based tactical strategy games, even calculating the unit's movement area requires a performance cost. Why? Because this algorithm is the combination of traditional exploration algorithm and game mechanics. In other words, an intelligent AI implementation will need to calculate the movement area of multiple units in the fraction of a second in which a unit decides to act, derive the results of unit interactions within the area, and find the number of cases with desirable outcomes. This task is not so time-consuming as to require load, but it is complicated enough to cause stuttering if processed with an old-fashioned single-threaded mode. Lost Eidolons has a visual effect and animation on combat interactions. So we implemented a multi-threaded mode to pre-calculate the next unit's action near the end of the effects, when the earned EXP appears after the target unit is defeated.
In tactical terms: How do you get the AI to act in an "intelligent" and coherent way with the player's actions?
Ocean Drive Studio: Well, it is difficult to validate and debug the implemented AI. The more detailed and complex the AI behavior patterns are, the harder it is to identify if the AI action during gameplay is the designed result or if it is malfunctioning. There were cases where we recognized a certain AI behavior as a bug and tried to inspect them, but it turned out that it was not. In some cases, we had to tweak the design of the behavior pattern so that it did not look like abnormal behavior in a given situation.
The implementation of AI in games has a well-established methodology. Behavior trees and state machines are the most commonly used systems for this task. Both systems are capable of making the AI appear more intelligent depending on how we configure the system, for example, in what detail the AI learns the game and responds to actions. You can configure the AI just to identify whether there is an enemy or not, you can have it evaluate whether there is an enemy with very low HP, and you can have it analyze whether there is one with very low HP under an abnormal state. If you design the AI to distinguish detailed situations and decide its reaction, you can make your AI more intelligent. However, more sophisticated conditions and reactions would require more complicated design work and implementation, so you need to find the balance.
"The more detailed and complex the AI behavior patterns are, the more difficult it is to identify whether the AI action during the game is the designed outcome or whether it is malfunctioning."
In tactical terms: Sometimes too simple AI can make the game monotonous and predictable, how do you make the AI unpredictable?
Ocean Drive Studio: An easy and standard way to do this is to apply randomization. You can implement a dice roll so that the AI randomly selects one of several options when reacting to a certain situation. However, there are not many situations where randomization is necessary. If the AI's behavior patterns are well designed, a small difference in game situations triggers different reactions, which can prevent a game from seeming monotonous. It is possible for the AI to respond exactly the same when a player does the same action in the same situation, and it is up to the game designer's choice whether the AI would give the same reaction in the same situation or not.
As we have seen, AI is the lifeblood of every turn-based tactical RPG. The strategies that developers program, the patterns and different algorithms, breathe life into the game. That is the case of Lost Eidolons, where Ocean Drive Studio has shown to know very well those techniques that work and has successfully implemented them in their game, resulting in a tactical RPG of enormous quality, hilarious and with a very tight difficulty.
This article helps us to better understand the work that exists behind the scenes, that work that is not seen as much as that of graphic designers and other artists. However, the figure of the combat designer in a tactical RPG is the central piece that moves the whole mechanism, and from In tactical terms I want to thank Ocean Drive Studio for the time they have dedicated to me, as well as their kindness at all times.
If you want to know more about this great team, you can do two things. First, buy Lost Eidolons. You have it on Steam at a very competitive price; this is the best way to get to know them, as their work speaks for them. And then, you can also follow them on Twitter. You will see that they are very nice guys!
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