At Soft Rains, world-building is at the heart of our creative process. This isn’t just about how we write; it unifies everything we do, from art direction to audio to game design. And if worldbuilding is the centre of our process, the player character is at the centre of our worldbuilding. Dalia, the protagonist of Ambrosia Sky, is a scientist first and foremost, so we’ve designed the ways she interacts with the environment to represent this. Beyond that, Dalia knows this place: she was born here, long before the crisis that prompts the actions of the game.
The core of Ambrosia Sky’s gameplay revolves around cleaning up after the alien contamination that has decimated the Cluster (the agricultural colony in the rings of Saturn in which our game takes place), resulting in mass death and a lethally overgrown environment. The cleaning gameplay isn’t the only central game system in Ambrosia Sky. Still, it is one of our biggest, so we wanted to spend some time talking about the different ideas that comprise our main gameplay verb: cleaning with a chemical spray and the alien contamination that you are tasked with cleaning up.
We’ve already seen people describe Ambrosia Sky’s core gameplay as a combination of PowerWash Simulator’s cleaning and Metroid Prime’s atmospheric exploration. You’re here to find the victims of the crisis and clean up the deadly fungus that killed them. But the alien fungus of Ambrosia Sky doesn’t want to be cleaned. It can hurt the player by shocking or burning them. It can also move, chase, and impede you through the environment. To help our fungus blur that line between enemy and environment, we’ve invented a voxel-like system where cleaning can be tactile, allowing you to carve a path through masses of fungus, but we’ll get to that in a minute.
First, let’s meet the alien contamination that has overrun the Cluster.
Meet the Alien Contamination
The alien fungus is the naturally occurring flora of our setting, The Cluster. Humans discovered it here roughly 90 years before the events of Ambrosia Sky. In classic human fashion, we colonized the Cluster, exploiting the local ecosystem, and thought of ourselves as its masters.
But this ecosystem is unstable. Players will also experience this instability in-game (the first mission, as seen in our demo, is a great example!). As players collect organic samples for study, the act of extraction will cause a cascading response from the environment itself, triggering fungal growths that are, quite frankly, a bit furious at you for disturbing their ecosystem.
Our alien fungus is both environment and enemy, but it’s also a deeply embedded part of our resource system and upgrade paths, as well. Internally, we’ve used the phrase “farm-to-table fungus”, referring to a type of fungus that exhibits specific behavioural patterns in the environment and can also be harvested to create specialized sprays (among other upgrades) based on those environmental behaviours.
To support this, our fungus colonies are composed of two sections: the main roots/stalk of the fungi, which comprise the majority of a colony, and the “fruit”. For the amateur mycologists among you, we use the term fruit here in the same way scientists distinguish a mushroom fruit from hyphae (or roots) of a mycorrhizal network.
For example, with our electric fungus, energized roots sprawl across walls and deal damage to unwary players. Along these roots, players will occasionally see stalks ending in crystalline fruit, which emit a dangerous area-of-effect.
Using either the sprayer or the tether, players can disconnect the fruit from the roots, neutralizing the threat it presents. This allows the fruit to be harvested and then used to upgrade your chemical sprayer. The most exciting upgrade enables Dalia to create an electric spray that can be used to create electric conduits and surfaces to conduct electricity to unpowered doors and similar devices.
An exploder fungus, on the other hand, well, explodes.
Acting like an abominable cross between a puffball mushroom and a proximity mine, exploder fungi expand the closer you get, eventually bursting into flame to protect itself. Harvesting exploder fungus fruit is a bit more volatile (thanks to its explosive nature), but becomes easier in zero-g, when the fruit floats more delicately in the air, rather than tumbling down and exploding upon impact. Like with the electric, players harvest exploder fruit by severing the fruit from its base, but with exploder, this is done by carving through the thick roots. You can harvest exploder fungus’s fruit to craft flammable sprays, which can kill fungus or spread fire to nearby flammable objects. Or you can set off a chain reaction of explosive fruit, letting the resulting fire burn away the large fungus colony that remains.
Jules Glegg (Technology Director) explains that,
… there are the simulation elements. We created a custom simulation system just for Ambrosia Sky, geared specifically to introduce the kind of hazards that matter in space — like fire — and to let Dalia use her creativity and know-how to manipulate those hazards in her favor. Ambrosia Sky’s simulation lets fungus interact very directly with the environment, for example by overloading an electric circuit that controls the exit door. It also gives clever players more ways to clean, like toppling a massive spire of electric fungus just by knocking its base out from under it.
This design approach gives us a lot of flexibility, allowing us to fill spaces with the alien fungus in interesting ways, creating traps and hazards that players have to contend with, and creating an interesting risk/reward of whether to carefully prune the fungus to harvest the fruit, or to clean the whole thing up to make progression easier. Below is a concept exploring the different layouts an exploder fungus could take to operate as an environmental threat.
Jules goes on to say,
Fungus is so fun to work on. It’s all familiar game development problems, in a totally wild new combination that throws out a lot of the standard solutions. First, there’s the problem of how to let a level designer build a colony, shape it to their liking, and trigger when it should grow. For this we use Houdini (a workhorse application for visual effects artists) and a cool example of nature-inspired math called the Space Colonization Algorithm. The resulting tool lets a level designer drop fungus into a level, set up areas for it to avoid, mark spots where they’d like a fruit to spawn, and then grow the colony right towards your face as you round a dark corner.
Making Cleaning Satisfying
In addition to making the fungus feel alive, compelling, and threatening, we also wanted to make cleaning it up feel incredibly satisfying. To clean up the fungus, Dalia is equipped with a chemical sprayer. It’s her primary tool, and its base spray dissolves organic material on contact.
Designing Dalia’s sprayer, both the look and the feel of it, was a lot of fun. We went through a variety of designs, some of which felt more like a pistol, and others that, quite frankly, felt more like my Dyson vacuum cleaner. With these explorations, we ended up somewhere pleasantly in the middle: a tool that feels powerful and effective, but is obviously designed for cleaning and restoration rather than combat (although it is helpful in combat, especially when your enemies are furiously sentient alien fungus).
The interaction between the sprayer and the fungus is key to making cleaning feel so good. The electric fungus is super brittle and shatters pleasantly on impact. But we wanted our exploder fungus, a much chunkier fungus, to feel different when it is being cleaned. We wanted the ability to carve out chunks of it, to be able to burrow through it even. So cue: Quantized Impact Field, our unique destruction tech. To explain Quantized Impact Field, or “QIF”, here’s Jules:
“Quantized Impact Field! QIF (pronounced “kiff”) is the tech that lets you clean fungus in precise chunks or even tunnel through large colonies. Lots of games have this kind of “volumetric” destruction, but we really wanted to find a way of doing it that avoids the usual tell-tale blockiness and supports Ambrosia Sky’s very hand-made, stylized art direction.”
Jules goes on:
“To give a little more detail — as you clean, QIF records every sprayer hit into a grid of cubes called voxels. That data is then used to change the physical collision of the fungus, so you can walk through the cool tunnel you just made, and also sent over to your graphics card where we use it to change the appearance of the fungus — melting it, crumbling it away, whatever the artists want it to do.”
In our next Ambrosia Sky developer log, we’ll take a look at the art direction and the decisions that went into giving Ambrosia Sky its distinct visual identity.
Jules Glegg is Soft Rains’ Technology Director, where she spends most of her time guiding the development of gameplay systems and wrenching on simulation code. Previously, Jules worked on League of Legends, Legends of Runeterra and VALORANT as a Principal Engineer at Riot Games. She is a co-founder of Trans Game Dev.
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