Check for the latest version on the [Discussions] Steam page in the [Events and Announcements] tab, or on the [News] Steam page.

For as long as I care enough about this game, I'm going to regularly update this guide to reflect new content and updates as well as add additional detail. It should reflect the latest stable release - there may be differences if you are playing on the beta branch, and it's always possible I missed something or made a mistake. If you haven't been playing for a while, you can find important changes down in the comments but I don't make an effort to keep a detailed changelog.


I saw that a lot of people new to the Robot faction get confused or frustrated with Heat when starting. It is not a particularly complex system, but it can indeed be unintuitive or unclear at times, especially at first contact. I expect you know the basics of Robots before continuing - this is to explain Heat, not how the entire faction works. Do note, while I provide some advice, I do not want to give a solution so you can skip the entire problem.

In this guide, I aim to provide an in-depth explanation of the Heat mechanics with some general advice. I do not want to call this guide complete because strictly speaking it's not, but it's really close to that. This is the foundation for people to start at a basic level and avoid simple mistakes, with all the technical information to help optimize. I want to emphasize, however, that you do not need to know all of the information below to competently play Robots. If you do not care much for optimization, going in and placing things based on vibes is fine as well, so long as you know the general rules, are prepared for some trial and error, and start off safe.

Heat output can be viewed in the building tooltip (when you hover your mouse over a building in the 3x3 building menu) and in the selection panel (bottom middle of the screen after clicking on a building).

The Heat map overlay becomes visible automatically when building. You can also toggle it with a button in the left corner near the minimap, and you can toggle numbers display with Tab. When you hover over a tile, its exact Heat and base Heat Reduction will be displayed on the left above the minimap (Heat-reducing buildings not included).

Below, the exact process of spreading Heat on a simple example (I recommend opening the image to read the text). Look below for the exact rules it works on, you can read them in any order. Images are still a work in progress, this specific image was done before Turbo Module Heat output was reduced, I will update it later.



Directions:

• Heat spreads in cardinal directions and diagonally in the same way, resulting in a “higher” spread distance diagonally. This makes many linear and asymmetric setups potentially significantly more space-efficient than square grids.
  
• Heat does NOT spread in straight lines only. The effective amount of Heat transmitted to a tile equals the highest amount of Heat transmitted from any of the 8 surrounding tiles, no averages or tracing.

In practice, this can cause a peculiar behavior where Heat “wraps around” better terrain or Heat-reducing buildings and causes overheating where we don’t expect it, particularly when building on bad terrain.

If you are familiar with the A* search algorithm, you can see that Heat spread can be considered in a very similar way, repetitively finding the tile from which the highest amount of Heat will spread and setting the Heat of surrounding tiles to that value (unless they already have a higher value from previous iterations).

Heat Reduction:

• Each tile surrounding a tile with Heat receives an amount of Heat reduced by a percentage. It is reduced on output, not on input - Heat Reduction of the source tile matters, but the target tile is irrelevant. This also means Heat Reduction works exponentially over distance.
  
• All effects of Heat reducing buildings (Wall, Heat Sink, Vent) stack multiplicatively with the tile's base Heat Reduction.

For example, a Rocky tile with 40% Heat Reduction with a Vent next to it that provides a 30% reduction has an effective 1-(1-0.4)*(1-0.3) = 0.58, or 58% Heat Reduction. It's generally easier to consider how much Heat gets to the surroundings tiles, so if a Rocky tile lets 60% of Heat out and a Vent does 70%, together that makes 0.6*0.7 = 0.42, or 42% (it is just 1 minus Heat Reduction in practice, but easier to calculate on the fly). I’ll call that Heat throughput later.

• Any amount of Heat below 0.4 is reduced to 0; this is particularly important because it means every building individually raises Heat in a limited and predictable area.

• Different Heat sources produce separate Heat maps that are then added on top of each other. In practice, this makes it way easier to calculate things, because we always get consistent spread distance for every building on a given terrain, only different cumulative amounts of Heat.

Combined with the 0.4 Heat cutoff, this makes it possible to create some incredibly dense setups, but may cause frustration because of abrupt spikes in apparent Heat generation. It is sometimes really cheap and simple to drastically reduce Heat in a setup and massively improve density and/or efficiency. In extreme cases, placing a single Heat-reducing building may be a difference between overheating and receiving no Heat at all.

This can be viewed in the building's selection panel after clicking on it.

• Buildings inherit the Heat of the tile they are placed on. Their own Heat output is disregarded for the mechanics that make use of this.

This is it for the basics of Heat. There’s not that much to say, and broken down this way the system is pretty simple. Most of the complexity arises because of specific buildings and because terrain rarely gives us large patches of the same tiles to work with.

Before going further, however, I cannot stress this enough - do not blindly trust the Heat preview when building, at least for now. It is a very simple preview that will not take everything into account, notably as of making this post it won't include ghost buildings (destroyed or being constructed), the Water Module's Heat Reduction, and Vent's Heat output.

This system is likely to be improved and refined in further updates.

It is not really possible to define a singular most optimal strategy for all tiles, mostly because their number is map-dependent and unpredictable, but it also largely depends on Captain skills, unlocked research, and may change depending on available resources. There are, however, some general rules I can mention that may be especially useful for fresh players.

Note that, because Heat Reduction from all sources always stacks multiplicatively, the types of terrain are much more impactful early in the game. Later on, using the three advanced Heat-reducing buildings (mainly Water Modules and Vents, but also Heat Sinks), it's possible to build very densely even on the worst types of terrain.

Dirt - 25% Heat Reduction
Avoid placing Data Centers there. Better put Data Processors, Modules, or anything that does not interact with Heat. Once you unlock Water Modules, Dirt is great for boosted Industry or Turbo Modules cooled with Water Modules.

Grass - 45% Heat Reduction
That's 26.7% on top of Dirt - it's a massive difference, especially before good Heat-reducing buldings are unlocked. If you don’t have better terrain available, put Data Centers there.

Lush - 60% Heat Reduction
That's 27.3% on top of Grass. This is where you’ll generally want to put your Data Centers early in the game, but most of the time it won't be nearly enough space for the FLOPs you need. Somewhat less useful later in the game since Water Modules don't affect it, unlike Grass.

Swamp - 65% Heat Reduction
Slightly more effective than Lush and appears in very large patches. Great tiles for Robots, but Swamps are map-dependent and usually difficult to secure so don’t count on those for early game.

Geyser - 75% Heat Reduction
Put Data Centers there if you can, or Nuclear Reactors if you're lucky to get one near Isotopes. They always appear individually and are generally too rare to be worthwhile for anything else.

Rocky - 40% Heat Reduction
Slightly worse than Grass, so it's a solid option for Data Centers if you don't have enough Grass and better terrain. Water Modules make this tile somewhat less valuable later in the game since they only affect Dirt and Grass.

Sand - 15% Heat Reduction
Generally not useful for anything Heat-related except a couple of specific tactics. You can put Data Processors or Industry Modules there as long as you avoid boosting the latter with Compact Reactors. Otherwise just place anything that does not interact with Heat here so that it doesn't occupy better tiles.

Whirlpool - 65% Heat Reduction
Great for placing Data Centers on desert maps, but still prone to creating fields of overheated Sand tiles since they tend to generate in small clusters and thin lines.

Mountain - 50% Heat Reduction
It's often a good idea to put Data Centers directly adjacent to them so they eat up Heat where you can't place anything anyway.

Crystals - 40% Heat Reduction
No comment.

Pit - 70% Heat Reduction
Heat-wise, same thing as Mountain tiles but better. You may also place Bridges there to allow your units to cross gaps, but this has to be considered carefully since Goo can also use them. Bridges also become way less useful later in the game when the Teleporter is unlocked.

Lava - 10% Heat Reduction
Do NOT put Data Centers anywhere nearby, nor anything else that generates a lot of Heat, without a lot of Heat-reducing buildings in between. That's a quick way to overheat half of your base if you’re not careful. Lava has some very specific uses and you can place Bridges on it, but in general it's the worst tile for Robots.

Water Ruin - 60% Heat Reduction
Does not matter for Heat Reduction in practice because it’s a very rare tile and you can only place a Lab here (do so, they provide massive bonuses).

This may just be the simplest part of the entire system.

• Regular and Advanced Data Centers.
  
• Data Processors.
  
• Industry, Water, and Turbo Modules.

If one of those is receiving more than 2 Heat, it overheats, reducing its output by 50% (rounds down). If it is receiving more than 5 Heat, its output is reduced to 0. In the first case, half a Heat icon appears over the building (like the branding image for this guide), and in the second case it turns to a whole Heat icon (like the one visible in the selection panel).

For details, navigate to the relevant section using the menu.
If a building is not mentioned here, it means it does not interact with the Heat system in any way, directly or indirectly.
Data Center - 20 FLOPs, 8 Heat, can overheat. Cheap, difficult to place densely.
Data Processor - 3 FLOPs, 0 Heat, can overheat. High price and upkeep, easy to place densely.
Advanced Data Center - 45 FLOPs, 12 Heat, can overheat. Expensive but efficient.
Industry Module - 6-12 Effort, 0/0.9 Heat, can overheat. Cheap.
Water Module - 4-10 Effort, 0 Heat, can overheat. Primarily used for cooling.
Turbo Module - 24-36 Effort, 1.5/2.4 Heat, can overheat. Great potential Effort per tile, but expensive and difficult to place densely.
Storage Tile Boost - Increased Module Effort production.
Compact Reactor Boost - Increased Module Effort production, Power draw, and Heat output.
Core - Effort production equal to 30% Module output in a 12x12 range, 0 Heat.
Smelter - 2 Heat, up to +100% Ore output at 15 Heat.
Nuclear Reactor - 20 Heat.
Flamer Tower - Up to +125% damage at 5 Heat. Fire damage over time unaffected.
Wall - 7% Heat Reduction in a plus ”+” area, does not affect source tiles. Cheap but ineffective. Great for walling off sections.
Heat Sink - 2 Walls in one, identical mechanics. Good effectiveness, but expensive, particularly in Ore. Great for walling off sections.
Adaptive Plating - A Captain skill that increases Heat Reduction of Walls and Heat Sinks by 30%.
Vent - Input Vent (30% Heat Reduction in a 3x3 area) + output Vent that emits Heat. Particularly great with Data Centers.
Water Module - Upgrades Dirt and Grass tiles in a 3x3 area, reduces Heat output of adjacent Modules. Particularly great with Turbo Modules.

Data Center - 8 Heat
20 FLOPs. Can overheat.
the basic source of FLOPs and the only big source of Heat early in the game. Has significant Upkeep and Power use. They are very cheap compared to other options, but it's difficult to place them densely before unlocking advanced cooling options.

Data Processor - 0 Heat
3 FLOPs. Can overheat.
On the surface, very bad cost-efficiency and much higher Upkeep for the same amount of FLOPs compared to Data Centers. They also need to be boosted by Compact Reactors to function. Lack of Heat output, however, allows great space efficiency on bad terrain (better on Sand than Data Centers cooled by Walls get on Grass). This makes Data Processors by far the worst FLOPs building in the long term, but they are potentially a great temporary solution before unlocking advanced options, particularly on more difficult maps with worse terrain.

Advanced Data Center - 12 Heat
45 FLOPs. Can overheat.
2.25 times higher FLOPs than the regular Data Center. More expensive, requires Crystals and Ore, but has slightly lower Upkeep for the same amount of FLOPs and easily gives better space efficiency than regular Data Centers or Data Processors once you know what you’re doing. By far the most space-efficient option for FLOPs, though regular Data Centers may sometimes be preferable since they're more cost-effective.

Overview
All Modules as well as the Core produce Effort ~3 times per cycle, and they produce 1/3rd of the displayed production at a time. All Modules have 3 levels - level 1 is the base output, level 2 requires the Module to be boosted by a Storage Tile or a Compact Reactor (more on that below), while level 3 requires both.
You can view the current production of a Module in its selection panel.

Industry Module - Base 0 Heat, boosted 0.9 Heat
6/9/15 Effort per cycle at levels 1/2/3. Can overheat.
The basic source of Effort. Prioritize boosting them with Storage Tiles, and only then consider Compact Reactors if you're on good terrain.

Water Module - 0 Heat
3/6/9 Effort per cycle at levels 1/2/3. Can overheat.
They do produce Effort, but they are not efficient at that role and very expensive compared to Industry Modules. Their main purpose is cooling buildings, and for that they are very good - all the densest setups for Effort production require either a lot of Water Modules or amazing terrain. Go to the Heat Reduction section for details.

Turbo Module - Base 1.2 Heat, boosted 2.1 Heat
24/30/36 Effort per cycle at levels 1/2/3. Can overheat.
Same general strategies as with Industry Modules, though you may want to place them densely on better terrain. Similar efficiency for FLOPs but potentially far more space efficient than Industry Modules, though some Heat management or very good terrain is necessary to make full use of that. Turbo Modules pair especially well with Water Modules since their Heat output can be easily reduced to zero.

Storage Tile Boost
+1 Module level.
Modules are boosted by adjacent Storage Tiles. Generally speaking, boosting should be prioritized over adding more Modules, starting from the early game as soon as we have spare Crystals. Later on, Turbo Modules should always be boosted since it's a doubled bonus and Storage Tiles are very cheap compared to them, but Water Modules can be skipped, especially if we are after high density.

Compact Reactor Boost
Industry Module: +1 Module level, +1 Power use, +0.9 Heat output.
Water Module: +1 Module level, +1 Power use.
Turbo Module: +1 Module level, +1 Power use, +0.9 Heat output.
Be careful with this when starting out, since the increased Heat output can be a trap - if you are not familiar with Heat mechanics, it's very easy to accidentally overheat your entire Effort production. The boost is applied in between connected pairs of Reactors and within a 3x3 area around each; it is on by default, but can be toggled. Compact Reactors need to be placed somewhere anyway so it can be a great option, but only if we have a way to deal with the Heat.

Core - 0 Heat
A late-game 2x2 building that produces Effort equal to 30% of Module output in a 12x12 area around it for a similar level of scaling to Human Life Support. 30% gives very little from a single Module, but the Core's FLOPs and Power use are fixed and very low compared to the Effort it can produce from 140 tiles total - it becomes worth its cost and FLOPs with just about 5-9 Turbo Modules in range depending how we calculate it. If possible, you should attempt to maximize their effects (no overlap, entire area of effect filled), but it's not that important since the difference is very small (in the order of ~3% less Effort per tile if you fill half of its area of effect, compared to theoretical maximum).

Smelter - 2 Heat
The source of Ore for Robots. Base production is 0.5 per Ore tile (or 0.6 with the Geologist Captain skill); that is increased by 100% at 15 Heat, capped at that value, and increased linearly in between. The game will always round the displayed number down to an integer, so don't rely on it for calculations. I heavily recommend heating up your Smelters using Vents or Nuclear Reactors later in the game; both variants of Data Centers can also work directly but it's difficult and expensive to reach the maximum 15 Heat without overheating the Data Centers. Note that Smelter's own Heat output does not affect it, just how Data Centers don't overheat themselves.

Nuclear Reactor - 20 Heat (2x2, source is the bottom tile)
The source of Isotopes for Robots. Base production is 1 per Uranium tile, which is half what the Human Processor produces, but the Nuclear Reactor does not require Crystals. It additionally produces 100 Power per Uranium tile, which makes it an amazing but limited Power source. That Heat output is high, but it's not nearly as bad as it looks if we place it on good terrain, especially on a Geyser. If it is placed on Rocky or better terrain, surrounding it with a layer of Walls 1 tile wide reduces Heat on the outside to less than 2.

Flamer Tower
Base damage is 4; it's increased by 1 for every 1 Heat and capped at 5 bonus damage, 9 total. In practice it does not make a big difference because the burning status effect that deals damage over time is unaffected.

There are 4 buidlings that can be used to reduce Heat, but there is no strictly best or easiest way to use them that will always work. In practice, the most effective setup varies and may be a combination of different Heat-reducing buildings; this depends mainly on the source of Heat and the terrain it's placed on. If we want to optimize, other important factors to consider are price and available space. Some setups may require a bigger or smaller rim of cooling or boosting buildings that makes placing small clusters much less efficient in both regards, but sometimes terrain, especially Pits, can serve as a great Heat barrier that costs nothing.

All Heat Reduction effects stack multiplicatively (including base tile Heat Reduction).

• Occupies 1/4th of a tile; can be lowered.
  
• Reduces Heat on the tile it is placed on and on 4 adjacent tiles (plus "+" shape).
  
• 7% Heat Reduction per Wall; Heat throughput for n Walls is 0.93^n.
  
• 13.51% Heat Reduction per Heat Sink; Heat throughput for n Heat Sinks is 0.93^(2*n).
  
• No limits to stacking - theoretically max. 20 effects per tile.
  
• Does not affect source tiles.

The effectiveness of Walls is poor, especially for dense setups, but they are cheap. They do not affect Heat Reduction on the source tile, so they are useful for creating Heat barriers between sections of the base but not much else unless we just have no other option yet. Note that lowering the Wall does not reduce its effect and allows units (including enemies) to walk over it.

Heat Sinks are an endgame variant of the Wall - they work exactly the same way, but they are twice as effective. They are outperformed by Vents and Water Modules in most cases, especially in dense setups since they cannot affect source tiles, but they are much simpler in use than Vents and don't have the restrictions Water Modules do. They can make very powerful Heat barriers to effectively separate sections of the base, but high Ore cost makes them the worst option economically - if density is not a priority, it may be better to just place more Walls instead since they cost no Ore.

Also note that you may build both Heat Sinks and Walls together on one tile. I don't expect this to be particularly useful at any point in the game though, unless you're after absolute maximum efficiency.

The Robot Captains can pick a skill that increases the Heat Reduction of Walls and Heat Sinks by 30% (and health by 10%). This means a Wall has 9.1% Heat Reduction and a Heat Sink has about 17.4%. The formulas for Heat throughput simply use 0.909 raised to a power instead of 0.93.

The effect is nearly unnoticeable for low numbers of Walls or Heat Sinks, but it makes a massive difference for dense Heat Sinks since its strength scales directly with the number of Walls (with each Heat Sink treated as 2 Walls). For example, it reduces Heat throughput for 4 Heat Sink effects from 56.0% to 46.6% (about 17% less), but for 12 Heat Sink effects it goes from 17.5% down to 10.1% (over 40% less), which may make a massive difference with the 0.4 cutoff. This allows to increase the density of many setups or reduce the required number of Walls or Heat Sinks, though Vents or Water Modules remain better options in most cases because of functional differences that are difficult to bridge just with bigger numbers.

• Does not block unit passage and cannot be targeted.
  
• Placed in input-output pairs at a maximum distance of 9 tiles (8 tiles in between).
  
• The input reduces Heat in a 3x3 area around the tile it is placed on, including that tile.
  
• 30% Heat Reduction per Vent input; Heat throughput for n Vents is 0.7^n.
  
• No limits to stacking - theoretically max. 9 effects per tile.
  
• Affects source tiles.
  
• The output emits Heat equal to the sum of Heat in a 3x3 area around the input Vent divided by 20 and deals damage every second in a small area (0.7 range) depending on its Heat.

Both the input and output cannot be destroyed and can be walked on by ground units. Outside their functions, they are currently only distinguished by tiny smoke particles on the output.

It is important to remember that the Vent costs Ore, has additional Upkeep and Power use, and its output takes up additional space which may significantly complicate layouts. However, its incredibly high Heat Reduction and the best stacking potential among all cooling buildings can be well worth all of those drawbacks. If we do not consider the space occupied by the output, the Vent becomes the most space-efficient general Heat-reducing building in the game by far. If we do consider it, the situation becomes more complicated, but it is still unmatched for dense setups, especially for Data Centers.

The Heat taken into account when calculating the Heat from the output Vent is not split or exclusive between overlapping areas of effect, but because of the reduction, you will get lower individual Heat output when you put multiple Vents close together, particularly directly next to a Heat source.

The exact value for output Vent damage seems to be 1 damage above 1 Heat, 2 damage above 2.1 Heat, and 3 damage above 3.5 Heat. It is solid against weak targets like Thrashers or Androids, but ineffective against stronger enemies, though it can always be used to complement other defenses similarly to Human Mines, particularly because Robots have much less options for area damage than Humans.

Module Heat:

• Reduces the Heat output of adjacent Industry and Turbo Modules by 1 flat.
  
• Technically no limits to stacking, but more than 2 do not have any effect even for Turbo Modules.

Terrain conversion:

• Affects tiles a 3x3 area around the tile it is placed on, including that tile.
  
• Does not reduce Heat directly, but turns Dirt to Grass (25% to 45% Heat Reduction - effective 26.7%), and Grass to Lush (45% to 60% - effective 27.3%).
  
• Does not stack - Dirt can NOT be converted to Lush tiles using 2 Water Modules.
  
• Affects source tiles, since tile Heat Reduction always does.

The flat Heat output reduction for Industry and Turbo Modules is (in my opinion) a much more important effect. It means one Water Module reduces Heat output of a Reactor-boosted Industry Module to 0, while two reduce the Heat output of a Reactor-boosted Turbo Module functionally to 0 (since less than 0.4 is then cut off). This makes them incredibly useful for any Turbo Module setup later in the game (much better than Heat Sinks and Vents in most cases) and allows to place Reactor-boosted Modules densely on any terrain, even on Sand.

Note that boosting Water Modules using Compact Reactors does not increase their Heat output, unlike it is with other Modules.

While Water Modules look great on the surface, multiple factors make them undesirable in many situations for buildings other than Industry and Turbo Modules. Significant FLOPs and Power use indirectly increase the costs and required space (especially in dense setups where the Water Module may overheat), while lack of stacking and terrain limitations make them sharply lose effectiveness on unsuitable terrain and when placed densely. Notably, they are also the only building in this section that ground units cannot walk over and by far the easiest to be destroyed.

All of that means Water Modules are by far the best option to use with other Modules due to the additional flat reduction, but they will be much less effective with Data Centers and other sources of Heat, enough that economically Vents often turn out very similar or even better despite their Upkeep.

If you've read the previous sections you already know my stance that there is no single best way to build FLOPs and Effort setups. That is not strictly correct, because I believe I have found the single most optimal endgame strategy, but there's still a lot of ways to get there and early game is arguably far more important.

It is not a lot, but in this section I want to roughly describe my own strategy for Robot economy.

- Research tier 0
Focus on Effort production, advanced resources (in that order if possible), and clearing the map - everything else is secondary. I usually place Industry Modules with Storage Tiles far away from Grass. Data Centers go on Grass tiles with a small amount of Walls in between to fit more of them. I usually don't boost Industry Modules with Compact Reactors, and instead put them around terrain and around other buildings like Storage Tiles and Assemly Modules to maximize Power output without occupying an obscene amount of space.

- Research tiers 1-2
The technologies from those research tiers are mostly military unlocks and utility, so I continue the same strategy as from the beginning, though I may use some of those to clear faster. If I'm lacking good terrain for Data Centers, I will use Data Processors on worse tiles, but it's preferable to use Data Centers since they are far more efficient - for that, clearing a lot of space is necessary.

- Research tiers 3-4
Turbo Modules are not great without Water Modules, so I usually skip them at tier 3. When I reach research tier 4 and unlock Water Modules, Turbo Modules become viable, but I usually don't place a lot of them unless I have a surplus of Crystals and Ore; it's often better to contiue placing Industry Modules to match rising FLOPs since they don't use up advanced resources. At research tier 4, Advanced Data Centers are also unlocked, and those are a priority since they are much more space-efficient than regular Data Centers and space tends to be the biggest constraint. I usually upgrade some of my Data Centers to the Advanced variant as soon as I can, and if necessary build as many Data Processors as I need reach tier 5 of research quickly.

- Research tier 5-6
The most important unlock at this stage is the Vent. I demolish the Data Processors I don't need and replace all or most of my FLOPs setup with one cooled using Vents, ideally on Grass - I tend to build Data Centers first, then upgrade to Advanced Data Centers once I start running out of space; while fairly expensive, this gives an incredible amount of FLOPs per tile compared to anything that can be achieved with Walls, freeing up a lot of good terrain. Once I have a good FLOPs setup, I build more and more Modules for Effort production - at this stage I prefer to fully switch to Turbo Modules cooled by Water Modules since they are drastically more space-efficient, and the production I have allows to get the Ore I'm lacking by converting Effort in Scrapyards.

- Research tier 7+
At research tier 7, two incredibly useful unlocks become available - the Mecha Tarantis is the best Robot unit by far, and the Core is functionally an Effort multiplier. It is important to push for it as fast as possible and unlock both quickly. All this time, I also continue building more and more Modules for Effort production since there is no such thing as too much Effort. Ideally, I want it in a layout that uses Turbo Modules, Water Modules, Storage Tiles, and Compact Reactors arranged in the entire area of effect of a Core to maximize both Effort per FLOPs and Effort per tile.

Units move faster over hot terrain. I have not tested the exact numbers for this, but the boost gets significant at high Heat values, though it is impractical to maintain over large distances. It does help with moving units across large distances in early- and mid-game but the Teleporter makes this drastically less impactful later on.

There is also a specific Stratagem (Metallic Transfusion) that makes robotic units regenerate faster while they are on hot tiles. Unlike the previous thing, it's a big boost - I believe it adds 1 regeneration per 0.4 tile Heat above 1, capped at 5 Heat (technically 4.8 because of rounding) where regeneration is increased 11 times. Because regeneration works only out of combat, it wouldn't let units tank a horde even if it healed fast enough, but it can be incredibly useful for clearing the map, particularly against the RFI.