Complete Vision of Progression in the Microbe Stage

This document will attempt to document a picture of the holistic progression of gameplay elements in the unicellular stage. It is similar to the Microbe Stage GDD in describing the various mechanics which will compose the unicellular stage, but is slightly different in purpose: while the GDD tends to explain each mechanic individually, this will attempt to describe how each mechanic will combine to create a fully engaging and realistic microbial evolution simulator.

I wanted to post a theory section on the forums but it made the post much too long, so here is a link to a Google Doc: Thrive: Complete Microbe Stage Progression Vision Theory - Google Docs

I recommend reading the above to provide reasoning for some of the suggestions I have made here, specifically in regards to my description of the early planet and prokaryotic strategies. I have pasted the gameplay aspects of my original document below onto this thread.


First, let’s discuss the various elements of Thrive’s gameplay design. We have aspects of…

  1. A Simulation - Thrive’s selling point is that it is meant to be a very accurate representation of evolution, informed by established scientific fact. The game’s scope is both limited to and as ambitious as evolution itself.
  2. A Sandbox - Thrive is meant to be procedural, and the narrative is meant to be driven entirely by the player’s response to the environment and competition from other cells. As such, replayability is an incredibly important aspect of the game.
  3. A Strategy Game - There is a clear lose condition - extinction - and a grand winning condition - reach the end of the stage. Evolution itself is meant to be a struggle against extinction, so naturally, there must be risk attached to the player’s decisions.


  • The beginning of a playthrough should have highly-present and dramatic environmental threats, such as eruptions, meteor strikes, and rapidly shifting environmental conditions to represent a young planet.
  • Various compounds, such as nitrogen, iron, and sulfur, should vary and dramatically shift to encourage flexibility and introduce risk and reward for player strategies.
  • Environmental threats compensate for limited intercellular interaction potential resulting from the simple nature of prokaryotes, especially in the early game.
  • The environment will begin to cool down eventually and compounds somewhat settle, around the time when players start settling into their niche. This will provide stability for complex lifeforms to evolve and will coincide with around where more unique cellular abilities evolve.

There are two primary threats the player must contend with: threats resulting from the player’s environment, and threats resulting from the player’s cellular competition. The player’s environment can provide a threat through shifting environmental tolerances, unstable resource availability, disasters, climate shifts, and other hazards. The player’s cellular competition can provide a threat through competition over vital resources, predation, and toxicity. The environment represents a more passive threat: a player must plan around it as it can be incredibly influential, but it doesn’t shift dramatically during a player cell’s lifespan. Cellular interactions represent a more active threat: although a bit less dramatically effective than the environment, a player must react to other cells in playthroughs constantly.

Imagine these two - passive and active threats - as opposites on a balance scale. In the beginning of a playthrough, we want the scale to lean more towards the passive threat - the environment:

This is because…

  1. The active threat isn’t yet developed. Prokaryotes, especially early-game prokaryotes, won’t have the unique abilities eukaryotes will have. They lack substantial size, are universally rather hard to catch with no abilities, and have limited threatening adaptations other than toxins. Just as in real-life, prokaryotic predation likely will be a novelty rather than a given. So it’s a bit of a stretch to assume prokaryotic AI cells will be able to carry the early game.
  2. This reflects a planet’s development. Young planets have yet to have their biogeochemicals fully mature, meaning unstable conditions. They also are transitioning away from the highly chaotic state of creation seen in young solar systems, meaning celestial events and bombardments are still common.

Then, as the game progresses, we slowly want to the scale to start teetering towards the active threat, until it gets to this point:

This is because…

  1. Cells will eventually get solid abilities. Especially when they become eukaryotic, other cells will present an unavoidable active threat.
  2. Stability is needed. If conditions are way too unstable, it would be hard for auto-evo, and the player, to create large, energy-heavy cells.
  3. Accurately reflects Earth’s evolution. The planet eventually stabilized, allowing life to become more complex throughout the boring billion, and ultimately, the Cambrian and onwards.

Here are some ways we can make the environment much more of a threat to the player in the beginning of the game…

  1. Rapidly Shifting Compound Concentrations - Perhaps having the most direct effects on gameplay, have it so that, along with glucose steadily dropping in concentration, the other “energy” compounds, such as hydrogen sulfide and iron, exhibit volatile shifts in concentration amounts. Having iron go from 7% to 5%, then 2%, then 0%, then 3% in a local patch forces players to stay on their toes and constantly shift metabolic strategies. Other compounds, such as hydrogen sulfide and sunlight availability, will also demonstrate these shifts as the young planet creates chaos. The amount these compounds shift can be inhibited based on difficulty.
  2. Environmental Events Turned up to 11 - Volcanic activity and meteor bombardments can have both larger environmental effects and direct gameplay effects. Volcanic activity increases local temperature dramatically through lava being spewed and, depending on scale, block out the sun. Meteor bombardments can also raise temperatures (although at a less significant rate), but can be more unpredictable. The frequency of these events can be dialed up heavily in the beginning of the game, thereby increasing unpredictability. There are rewards for staying in volatile environments, however; volcanic activity releases a heavy amount of phosphate into the environment, while meteor strikes can introduce a variety of unique and essential resources.
  3. Pivoting Environmental Tolerances - The primary environmental factor at play in the early game will likely be temperature. The oceans will start off slightly warmer than they usually are, and will gradually cool down. However, environmental events, from bombardments to increased temperature volatility, can dramatically heat up several patches at once. Perhaps we might introduce acidity as an additional environmental compound to track, although we would probably make the effects of acidity much more passive than the effects of other compounds.

After a while, environmental events will reduce in frequency, until they reach a “normal” level, and compounds will largely stabilize around a baseline amount which doesn’t exhibit much variety. This will allow players to start becoming more comfortable in their niche, and thus, more likely to experiment.


  • The early game phase of many strategy games, such as Civilization, represents a less-volatile, but still urgent period where the player’s decisions can make their near future either much more successful or difficult.
  • The beginning of the entire playthrough, the prokaryotic phase should represent the player staking out their immediate niche on a young and unstable planet.
  • Because prokaryotes are simple and small, the early game likely won’t have a plethora of prokaryotic abilities, hence emphasizing the need for the environment to step up and present a threat to the player.
  • Emphasize reproductive costs and population for prokaryotic players, rewarding players who maintain a solid population with a bigger margin of safety from extinction. Will help them when their population inevitably reduces a bit as they increase in size and prepare for the nucleus.
  • Demonstrate the worldbuilding effects of bacteria by having local compound concentrations be somewhat affected by the presence of certain parts, and potentially attaching gameplay effects.

The description of the early game from above - an unbelievably volatile environment where nothing is really certain - will have strong implications on evolution, and thus, how the player approaches Thrive in the early game. To review…

  1. Compounds will be unstable, meaning the player will be wary of becoming too dependent on a source of energy too quickly
  2. Environmental conditions will fluctuate, meaning the player will be constantly attentive of the climate.
  3. Disaster events will be very common, meaning the player will have difficulties in predicting the state of their planet.

This paints a very chaotic picture of the early game. And while we currently do have an issue of the first few stages being rather mundane, it is important that the player has enough information and capability to ensure that they may have a fair chance at survival. Thus, it is important that we emphasize a strategy of sorts in the early game.

Inspiration From Other Prominent Strategy-Sandbox Games

I would like to discuss a very good strategy game franchise which has achieved prestige in the gaming community, and which we can draw considerable influence from even in the cellular stage: Sid Meier’s Civilization. In it, you assume control over the fate of a civilization, and must respond to other civilizations by using the resources and cultures available to you to maximum effectiveness.

Although a bit less volatile, the beginning of a game of Civilization has some notable overlaps with the beginning of an ideal playthrough in Thrive…

  1. Civ-to-Civ Interactions - The player and other civilizations have limited means of interactions due to a limited set of abilities.
  2. Environment’s Role - The environment is filled with resources and ideal settlement sites, heavily influential for the success of a civilization in the early game.
  3. Form of Competition - As such, the primary means of competition is racing against other players to explore, settle in the best spots, and thus, intake the best resources. Although war is technically an option, it is almost universally unrewarding this early due to limited production and technological capabilities.

That’s it. Although simple, that is how Civilization makes its early game incredibly engaging - many players often cite the early-game phase as one of the most exciting parts of an entire playthrough. There are a wide range of strategies and play styles which result from these conditions, including two prominent elements…

  1. Rushing settlements, creating many cities to gobble up as many resources as possible with the risk of neglecting other important traits, such as culture, and spreading your army thin.
  2. Investing heavily in your initial city, so that you increase the number of abilities you have and are able to inflict punishment on other Civs.

Players will oftentimes balance between these two options. A certain player might aggressively settle a city on a resource close to another Civ’s cities, risking a reduction in loyalty and military aggression but cutting off the other Civ from a potentially influential resource. Another player might settle a few cities around themselves, but go through a phase of investment once they are satisfied with the amount of territory they have gobbled up. Another might settle every piece of land they are able to find. Plenty of options, simple conditions.

Applications to Thrive

Breaking down Thrive into similar parts can help us get a clearer image of the gameplay elements we should emphasize in the early game…

  1. Cell-to-Cell Interactions - The player and other cells have limited means of interactions due to a limited set of abilities.
  2. Environment’s Role - The environment is filled with resources, although conditions are constantly changing, meaning these resources are in flux.
  3. Form of Competition - As such, the primary means of competition is racing against other cells to efficiently gather as much of a given resource as possible. Although predation is technically an option, it is universally unrewarding due to its limited ATP benefits and difficulties in becoming an effective prokaryotic predator.

Just as is seen in Civilization, Thrive’s early stage is much more passive in competition than the rest of the game might be. With limited offensive capabilities besides toxicity, the player must resort to using their environment to position themselves ideally within their environment. Just as is seen in Civilization, the first rounds in a playthrough represent the player’s attempt to establish a solid niche on a new planet, meaning the beginning of Thrive is all about potential and forward thinking.

Brief Discussion of Toxins

Another potential form of competition for prokaryotes will be the use of toxins, which, as previously mentioned, covers “contest” competition in prokaryotes. For prokaryotes, toxins should extend past pure gameplay and high a decent effect on auto-evo population numbers. This allows players to adapt means of competition against other prokaryotes occupying the same niche, and also will mean that the player must be aware of their immunology.

What is at Stake in the Early Game?

Before delving into the strategy behind the prokaryotic stage, let’s clearly establish the risks and the rewards at stake as a result of the player’s performance in the early stages. In Civilization, the reward is an abundance of resources and territory, which makes the development of science, culture, and military power much easier throughout at least the first half of the game. The risk, on the other hand, is letting go of these benefits, and thus, being at a weaker position to wage war, develop culture, and research in comparison to other players. The ideal is becoming a superpower, the worry is becoming a Civilization which is easy to bully.

In Thrive, the ultimate risk is extinction, so the reward should be a state which minimizes the risk of extinction: a high population. Population is a somewhat finicky performance metric however because as your creature increases in complexity, its population will naturally decrease as well; it doesn’t necessarily mean the player is less successful or is at an exponentially higher risk of extinction. In fact, fitness is perhaps the objective standard of measuring a species’s potential success in evolution, whereas population is a performance metric which could, but isn’t necessarily, an indicator of high fitness. So there’s an ambiguous balance there between losses which come as a result of worse performance, and losses which are inevitable.

As such, before we discuss strategy, it might be worthwhile to pay a bit more attention to clarifying the impact of the performance metric - population - to the player. Here are some ways I think we can achieve this…

  1. Explicitly Tell the Player How Many “Lives” They Have - Having a bigger population lets the player die more without risk of extinction, but the amount of times the player can die isn’t very clear. We should somehow let the player know that at x population, they have y amount of lives.
  2. Let the Player Play in any Species-Inhabited Patch - Already planned, this will add a tangible reward to higher population distributions. Instead of having to move around the map patch-by-patch and having to react to each patch on the way, the player can hunker down in a specific patch and make their species adapt to the environment they feel is most stable. This should probably be coupled with an increase in non-player guided migrations.
  3. Reduce Total Population Lost from a Death at Higher Complexity Levels - This shouldn’t be too lenient, but it emphasizes the fact that, rather than raw population numbers, fitness is the ultimate indicator of survival.

The above should provide tangible benefits and a fair balance behind population which reflects its role in evolution: a performance metric, but not necessarily the most definitive indicator of a species’s success. It also provides a clear reward for the player which will last for at least the entire microbe stage. Since it becomes harder to rapidly gain population as time goes on in the microbe stage…

  1. A more successful beginning will result in a higher population, which means more lives as you begin to experiment and gain complexity, which means a bigger cushion between the player and the losing condition: extinction.
  2. A less successful beginning will result in a lower population, which means less lives as you begin to experiment and gain complexity, which means a bigger cushion between the player and the losing condition: extinction.

Prokaryotic Strategies

Now that we have a clear understanding of what the player is gaining or losing depending on their early game performance, we can discuss strategy. With the listed conditions and stakes, I can see strategy essentially being a balance between these two decisions…

  1. Remaining small and uncomplex so that you may easily pivot metabolism towards whatever resource is most available. Safe, but it means you can potentially be beaten by another species in competition for resources.
  2. Specializing early on to progress rapidly. Comes with the risk of making it harder to adapt in case of rapid fluctuations in environmental conditions, but can result in staking out a strong position in your niche.

For example, one player can remain small and simple throughout the volatile early game, letting go of a potentially large population but ensuring they are flexible enough to not die out. Another player can rapidly specialize around hydrogen sulfide early on, allowing them some unique abilities and enhanced mobility. If it works, they have a headstart on the rest of the competition and have more wiggle room in the near future; if it doesn’t, they can take serious blows to their population and edge their species closer to extinction.

Thus, a critical component of the early game is timing: knowing exactly when to exit the safe and simple prokaryotic evolutionary strategy and pivot towards gaining complexity, and timing that switch so that you can maximize your claim over the rest of your competition. You can either be blazing ahead as a dominant species in your niche, or trying to break into a niche with other strong competitors depending on how well you’ve timed your switch. This, coupled with managing the dramatic shifts in environmental conditions, will surely provide a challenge for players to deal with.

Environmental Effects of Prokaryotes

It would also be worthwhile to attach environmental effects to the various metabolic strategies. Hydrogen sulfide chemosynthesis results in sulfur, which can increase localized water acidity and negatively affect organisms with calcium-carbonate membranes. Iron respiration can result in more oxygen build-up, as less iron is available to interact with the particle, thus resulting in more free-floating oxygen. Photosynthesis and aerobic respiration form a feedback loop, with the oxygen produced from photosynthesis via carbon dioxide feeding oxygen-breathing organisms who release carbon dioxide as a waste product. And nitrogen fixation can result in an increase of free ammonia, though its phobia of oxygen can make access to this bonus nitrogen difficult to see as the oceans become oxygenic.

There are various ways we can demonstrate the atmosphere-building effects of prokaryotes in Thrive, it’s just a matter of how intricate we want to get. Since prokaryotes will naturally have a smaller population due to their smaller size, it is likely that the majority of metabolic activity could be taken up by bacteria. I say introducing factors which relate to the level of oxygen is enough, which includes heightened levels of iron in the surface initially blocking heavy build-up of oxygen, population blooms of algae potentially resulting in dipping oxygen levels, and the creation of an oxygenic atmosphere as photosynthesis develops.

Synopsis of Threats a Player Will Face as a Prokaryote

  • Heavy fluctuations in compound availability in early game
  • More dramatic and frequent disaster events in early game
  • Shifting environmental tolerances
  • Tug-of-war over resources with other species
  • Potent toxicity


  • World events will ensure that a player can’t just get to a certain point in the early game and cruise after their young planet calms down.
  • Build up of free oxygen will be slightly delayed, but will pave the way for oxygenic respiration and complex life, empowering the most potent form of respiration known but also forcing some cells to anaerobic environments.
  • Pacing the rate of oxygen buildup will be important in determining the length of the microbe stage and early multicellular stage.
  • Glaciation events will be occasional and will result in widespread cold conditions, killing off some cells and making room for competitors. Increased phosphate/ammonia after provides a soft reset of sorts.

After a while, the hellish conditions of the early planet will stabilize. Compound amounts will settle around an average, and will become slightly more predictable in terms of forecasting available resources. Cells will be able to reliably gain some means of complexity as they specialize slightly around a preferred energy source, and ecosystems will reach some form of stability.

Even after this initial state of chaos however, the planet will still go through growing fits as a result of the proliferation of life which can upset established environments. Oxygenation and Snowball Earth Events will have heavy implications on the development of life, initially dramatically upheaving life, but eventually providing excellent opportunities for survivors.

Oxygenation Events

Oxygenation events generally denote periods of time in Earth’s history where, for some reason or another, oxygen levels rapidly rose. There were more than one instances of rapid oxygenation as far as we are aware, but there is a great oxygenation event, which indicates the arrival of free-floating oxygen, and various other smaller oxygenation events, which indicates points of time where other major oxygen reservoirs began to be filled out, indicating a greater rate of free oxygen production. And just to clarify, an oxygen reservoir is essentially a natural sink of oxygen, like iron or the continents - once the amount of said reservoir is used up through reactions (such as the formation of rust), that sink has no more space, meaning oxygen begins to build up in the atmosphere - which is what is needed for aerobic respiration.

We should be able to pace the progression of the late Microbe and Early Multicellular stages by pacing these oxygenation events, as all highly-potent forms of metabolism are aerobic in Thrive (as is seen on Earth). The first oxygenation event can introduce enough oxygen to make the surface patches decently aerobic, but the extent of this oxygenation likely won’t reach to sub-surface ocean patches just yet. This allows players who for some reason are not yet ready to become fully aerobic to find some shelter and presents a unique environmental shift on surface patches while reflecting evolutionary history. Future oxygenation events will then spread oxygen further across the ocean (the full oxygenation of deep oceans was estimated to have occurred maybe around 750 million years ago) while the surface patches simultaneously rise up to modern levels, further increasing the viability of aerobic respiration. There were around 3(?) oxygenation events on Earth, so we have some flexibility in determining how fast this progression should go.

Oxygen has dipped at certain points in Earth’s history, notably after the Carboniferous - the peak of Earth’s oxygen content, leading to consistent and widespread wildfires - and amidst Snowball Earth events - due to the dying off of cyanobacteria. We can probably have oxygen dip at some points in a playthrough, but because oxygen is so heavily tied to progression, we also want to ensure that oxygen can never dip too low after reaching a certain point. Perhaps once oxygen reaches a “checkpoint”, it can no longer go below that value. So if atmospheric oxygen levels reach 5%, it can never dip below, say, 2%.

Another thing to note is that oxygenation events should affect the availability of iron near the surface patches of the ocean. Iron was much more common on the ocean surface before the spread of oxygen, hence its reservoir status.

Snowball Earth Events

Snowball Earth events are intense glaciation periods where most, and perhaps, all, of Earth’s surface is covered with ice and snow. Temperatures dip below freezing in places we wouldn’t expect them to. The most direct effect a snowball Earth event has on life, other than cold temperatures of course, is lessened photosynthetic productivity. In places where the ice is thick enough, not enough light goes through to sustain a large photoautotrophic population - which not only has a strong ripple effect on an entire ecosystem’s food web, but can also lead to a lessened presence of oxygen.

Snowball Earth events in Thrive could essentially be represented through a total or near-total presence of frozen patches in the player’s map. Because ice would be thinner near the equator, those patches would likely allow more sunlight through.

Snowball Earth events, and similar global disasters, essentially serve to upset the existing balance of power. They have the capacity to wipe out species that are otherwise very successful, opening up niches to new and potentially more competitive organisms. Such conditions could have played a role in the rise of the eukaryotes.


  • Endosymbiosis will first be a tool for prokaryotes to catapult themselves towards complexity, and then will be a tool for eukaryotes to quickly unlock a desired organelle.
  • Endosymbiosis will make it easier for the nucleus to be acquired, from there allowing the evolution of various eukaryotic abilities.
  • The ideal “strategy” behind endosymbiosis will probably be to have your first organelle be an energy-producing organelle.
  • Endosymbiosis will probably serve as a major catalyst marking the start of the Microbe stage’s peak in terms of action and complexity.

As was discussed in the theory section, endosymbiosis was the critical phenomena needed for life to break past the constraints surrounding prokaryotic evolution, rapidly allowing organisms to supercharge their metabolisms with massive energy-production. It led to the formation and sustenance of the nucleus, and thus, the eukaryotic kingdom as a whole.

As was discussed in the larger upgrade thread on the dev forums (Upgrades, Unlocks, & Endosymbiosis Master Thread) , endosymbiosis will essentially be a contrived process which will let a player reduce another cell into its bare components over a couple of generations until they unlock a desired organelle. As currently conceptualized, players will select a certain AI cell to begin endosymbiosis with. Said AI cell will be able to be converted into a type of organelle depending on its composition - so a cell which is composed of metabolosomes and toxins will be able to be converted into either a toxin vacuole or a mitochondria. Certain cells are more ideal candidates for a certain organelle than other cells, and will be converted into a specific organelle faster. For example, if a cell has 5 metabolosomes and 2 chemosynthesizing proteins, it would take maybe 3 reproductions to convert the cell to a mitochondria, and 7 reproductions to convert the cell into a chemoplast.

Players will probably be naturally incentivized to make their first organelle a metabolism-related one. Since more advanced parts like toxin vacuoles and the such will represent decently sizable costs, and since the nucleus itself will require a lot of ATP generation to be evolved, an energy-focused part will generally be the best and most broadly-applicable decision to go with. This will smoothly represent existing theory, with mitochondria being the first organelles to have evolved.

Once unlocked, the nucleus will allow you the ability to create more organelles out of endosymbionts. As is currently designed, unlock conditions for organelles, though definitely feasible, require a decent amount of commitment in terms of fine-tuning your organism’s morphology. Endosymbiosis will allow you to create organelles as long as you find a solid cell to make that organelle from. So, endosymbiosis really will serve as a fasttrack unlock condition of sorts.


  • New combat abilities (many listed here: Comprehensive Combat Revamp - #7 by Deus) will allow for advanced food chains to develop, increasing the threat of other cells.
  • Complex relationships, such as predation, will emerge, naturally carrying over to the macroscopic stages and shifting focus to active threats.
  • Except from world events, the environment will shift roles from being a threat to a constraint.

Naturally extending from endosymbiosis, the eukaryotic phase of the Microbe Stage will represent its peak, allowing players the ability to adapt various cool abilities. Predation will become a viable strategy due to the size and complexity of eukaryotes.

Because the eukaryotic stage of gameplay generally represents the state to which a player is progressing to in the cellular stage, this part of the document will be rather short. But one thing I would like to note is that, with the emergence of solid cellular threats, the impetus of providing challenge can be shifted away from the environment and towards other AI cells.

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This is already in the game, though? Unless I’m misremembering we got this in already in 0.5.9 (but definitely should be in the just released 0.5.10) that the player can move to any patch their species is in or next to in the editor.

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Ah, I think I read that patch note and just assumed this patch relocation only occurred after a patch-extinction, and thus never tried it in game. That’s very good news nonetheless!

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