Building a flexible combat system for Aether & Iron

Chaos Theory Games was founded in 2012 to improve quality of life and inspire a more sustainable future through the magic of play. Over the past 13 years, they’ve released games including Crab God, Blendy, and Lifty.

In 2023, Seismic Squirrel engaged Chaos Theory Games to help bring their vision for Aether & Iron to life – a narrative-driven RPG set in sky-high New York City, where players explore a fractured world and build relationships. It’s a classic noir story with a sci-fi twist: What if humanity discovered the technology to defy gravity and had launched their cities into the sky?

At the core of the game is a tactical, grid-based vehicular combat system where players control a squad of customizable vehicles in turn-based road battles. The system was designed for combat to feel strategic and cinematic while feeling integrated with the game’s branching narrative choices and worldbuilding.

To create the feeling of a car chase, the environment needed to be constantly moving during combat, which presented the team with design challenges. After much iteration, they knew they had to develop a flexible combat system to build many different types of fight encounters that support the game’s narrative.

We sat down with James Lockrey, managing director at Chaos Theory Games, and Elric Milton, one of the game designers, to discuss the challenges they faced, along with the solutions they found to overcome these hurdles.

Choosing vehicular combat

The Chaos Theory Games and Seismic Squirrel teams had a very clear vision from the beginning. They wanted a flexible system to help create a combat experience that felt thematically grounded, mechanically deep, and distinctly different from other turn-based RPG combat games.

“The system combines vehicle movement, positioning, and the driver’s abilities into a tightly-paced loop. Each combat encounter is deadly, decisive, and usually over in four to seven minutes,” says Lockrey. “The combat uses vehicles instead of people and its vehicular setting, combined with lane-based turn structure, creates a kinetic rhythm where the environment plays a much larger role.”

With nonstop movement, static environmental effects only took place in certain turns. The activity caused hurdles with background elements, clarity, and the readability of lane-based movement. Lockrey adds, “We want to offer the community something that is rarely seen in a tactical combat RPG and that brings challenges. We didn’t have much reference material from other games, so we just kept iterating until we were happy.”

Taking the wheel on prototyping

The Chaos Theory Games team began development by creating an initial digital prototype to test the core premise. They further developed this with paper and Miro prototyping to analyze changes to some of the core stats like action points and movement. “Early on during prototyping, we used a fair amount of Asset Store assets like DOTween. While temporary, they were really helpful for starting quickly,” says Lockrey.

The team then created some video mockups that suggested features they hadn’t built yet. This helped to unify them on how the combat would feel like a car chase. They developed features and in-Editor tools to make it possible to build and test encounters.

“We built more than 150 unique vehicle configurations.” – Elric Milton

“We could visualize upcoming road and transition changes in the Editor. We wanted to ensure that every combat encounter could be played from within the scene and roughly represent the player’s progression,” says Milton.

“We used Behavior Designer and some grid system plug-ins and tools like Terrain Grid System 2 to help with quickly getting a turn-based combat prototype together, which I think we did within the span of about a week. This was essential,” says Milton.

Visualizing combat design using Gizmos

The team’s vision solidified even more as prototyping progressed. “We knew we had to design around limited actions and high-stakes choices, and that every move should feel meaningful,” says Lockrey.

They wanted to capture a feeling of a car chase, but were initially stumped on how to build a slower and thoughtful turn-based combat system where players are given time between each action to really think about what they’re doing. Lockrey explains, “How do we make that be a primary part of the combat mechanics? Players are thinking about lanes opening and closing, and about how to initiate a chain reaction of environmental obstacles to get in their opponents’ way.”

“We were able to create our first draft of each combat encounter within a day.” – Elric Milton

To visualize a grid that changes at runtime every few turns, they used Gizmos in the Scripting API. “These were super useful. At the start, our combat was prefabs and assets in the scene and we very quickly evolved that to be everything spawning in from code,” says Milton. “To design combat encounters, I needed to be able to visualize everything. Almost the entire combat scene is displayed in these little basic colored Gizmos and lines. This was vital, especially when it came to the grid transitions going between one really wide lane to multiple smaller lanes connected side by side.”

At the outset, the team decided that it would be the vehicle that’s customizable instead of the character. Each vehicle is made up of a range of parts like engines, repulsors, weapons, armor, and storage. In every combat encounter, opponents are also driving vehicles that the player can access, along with their parts. Players then earn loot after the battle that may include parts or scraps of a vehicle.

To manage this inventory of items, they selected the Opsive Inventory System. “I used it a lot when putting together vehicles,” says Milton. “It was key for stat adjustments and deciding which pieces the cars and opponents needed to be made up of. I used it for almost every part of the combat.”

Merging art and design

For the team, an integral part of building combat in the Unity Engine was the separation of logic and data, which allowed devs, designers, and artists to work in parallel.

“Each combat scene had a series of ‘managers’ that controlled the logic for that scene – transitions, environment, etc.,” says Lockrey. “All of the characters and vehicles were separated and composed in a separate ‘vehicle designer’ Editor.”

The team plugged vehicles into each encounter's spawn slot, selected specific characters and sets of skills and abilities, and then mixed and matched these elements to create new combat encounters.

“Each vehicle also has references to all the visual and creative elements (e.g., VehicleVisual, VehicleSFX), so these can be worked on separately. We started with placeholders for the vehicles and then artists replaced them slowly over time,” says Lockrey.

Some of the key turning points of combat from a design and visual perspective included turning the grid to be angled, adding in-road transitions, extending the grid, and adding cinematics, cutscenes, and status effects.

On the design side, there was a heavy use of ScriptableObjects to bring a lot of flexibility to the combat. The art team also used Timeline and Cinemachine to enhance the cinematics and camera control.

“On the art side, the game uses a lot of 2D and 3D elements. There are approximately 60 to 70 hand-painted 2D environments, which we’re really proud of,” says Lockrey. “Since many of our artists have film backgrounds, there was a lot of high-fidelity environment illustration going on.”

“We reduced the implementation time for technical art for act 2 and act 3 combat environments by 60-70% when compared with act 1.” – James Lockrey

Since the combat elements are in 3D, there’s a 3D representation of the city with an almost isometric view. “The art team relied heavily on Shader Graph and VFX Graph to create some of the visuals and effects for weapon firing animations, combat abilities, and road effects. They helped give each environmental hazard a distinct and readable look,” says Lockrey.

Making combat a part of the story

Aether & Iron is a very story-driven game, with between 200,000 and 250,000 words of dialogue and more than 100 characters. It was very important to the team that combat felt like a part of the story. They wanted to incorporate narrative consequences into fight sequences so that narrative choices affect battle encounter design, and combat outcomes affect narrative branches.

The team realized that having bookend conversations at the beginning and end of these encounters helped to maintain the flow. “We added combat barks and interactions between characters and encounters to add some flavor,” says Milton. “In limited places, we also included abilities for what players can do in the combat encounter to affect branches or outcomes.”

As well, they built custom cutscenes for almost half of the combat encounters to lead either into or out of the combat encounter to help with some of the storytelling key beats. “We also used Cinemachine and Timeline here since some of these cutscenes happen during dialogue,” says Milton. “Players can make some choices in dialogue that will determine the next animation or branch of the cutscene, so it’s not all just one animated sequence. Some of them are broken up into happening across multiple stages, and there’s a little bit of connective tissue between dialogue system beats and timeline sequences.”

Feeling grateful for the lessons

After years of development and problem-solving, the team looks back on their experience with optimism and pragmatism.

“We learned how critical camera work was to making slow, turn-based combat feel exciting and high stakes. Early on, we felt like cars in a tactics game would translate one-to-one pretty easily,” says Milton. “Turns out a lot of work was required to make it believable. However, it also gave us new ideas that couldn’t exist in a stationary setting – obstacles that rush by, environment transitions, and cool action movie-style slow-mos.”

With the game coming out later this year, the team is excited for the community to take it for a spin.

“We hope they feel like it’s fresh, thoughtful, and thrilling,” says Lockrey. “A real cinematic experience where every encounter feels handcrafted and tells a story.”

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