FAQ from Discord

This is a page of frequently asked questions (FAQs) from the Discord Development server and their answers. Most of the questions are focused on player concerns, but the answers often involve either developer insight into the logic of the game, or the development history as to why a certain feature is the way it is.

See also the Frequently Made Suggestions, which have some overlap with these questions.

Table of Contents Management and co ordination of the CDDA project Discord Servers Game focus and direction Launchers, mod packs, and optional content The (3rd-party) Launchers Mods and Mod Packs Your character Avatar Time and Ticks Mutations CBMs Combat Options Items Bows and Arrows Books Guns Maps and the Reality Bubble Map Terms The Reality Bubble Z-levels Zombie Hordes Monsters Zombie Evolution Buildings Powered Buildings Vehicles Fuel Consumption Vehicle collisions Flight training and building aircraft Alternators and Foot Pedals Vehicle Design Formula

Management and co ordination of the CDDA project

Discord Servers

Question: What's with all the CDDA themed Discord servers? Which ones are official and how do they differ?

(by Kevin Granade, project lead)

The first "CDDA discord" was not affiliated with the project in any way, and was only tenuously CDDA oriented, it was more of a random social club type chat server that happened to have some CDDA themed channels. Over time it became steadily less friendly to the project, culminating in a bizarre incident where one of the mods screwed with the role settings for the CDDA developers for no apparent reason. At that point we made the "Cataclysm: Dark Days Ahead" development server and development talk moved there.

A bit later there was a bizarre incident where an apparently random member was muted on the server for being a jerk, then appealed to the server owner (who was almost completely absent from the server), who bizarrely made the random guy the new head mod and removed the moderation powers of most of the existing mods.

Those mods promptly left and formed a new fan/chat oriented discord somewhat more centered on dda, the "Cataclysm: Dark Days Ahead Community" server.

The new head mod for the old discord server is a notorious troll in the roguelike community, and because of that pretty much everyone immediately cut ties with the server. That server has steadily gone downhill under the moderation ideal of, "say anything that won't get our server dissolved by the discord admins, as long as a mod doesn't dislike what you have to say".

Too long, didn't read: The "Cataclysm: Dark Days Ahead" development server is directly managed by Kevin Granade and trusted senior developers and is the official server for CDDA development. Gameplay discussion is allowed but there's no general social community and the moderators discourage non-development social channels. The "Cataclysm: Dark Days Ahead Community" server is managed by some of the same moderators as the development server and various senior developers spend time there. It is CDDA focused, but has social channels if you just want to meet people. Any other CDDA themed servers aren't associated with the CleverRaven team and a few of them are pretty toxic, but each person is going to need to make their own decisions about which servers they want to be on.

On the development discord server, what are the differences between contributor, collaborator, dev team, moderator, merger, and Kevin?

(by mlangsdorf, the current vehicles maintainer)

• A contributor is anyone who has contributed by successful submitting a change that got merged, and then who asked for the contributor.
• A collaborator has contributed enough and been a voice for reason and sanity on the development server that the senior dev team wants to acknowledge them as someone who should be paid a little more attention when they're discussing other people's contributions and technical issues
• A member of the dev team is someone who has has collaborated frequently and well enough to have significant sway over the direction of the project
• A moderator is a member of the dev team who has decided to help wrangle the herd of cats that chats on the development server.
• A merger is member of the dev team with keys to the car. They can add (merge) new contributions into the CleverRaven git repository, making the contribution officially part of CDDA.

Although the roles exist, game development is not strictly hierarchical. A good argument from a nobody wins over a bad argument from a member of the dev team. We value getting the right answer over your (our) position in the hierarchy.

Mergers and moderators aren't special within the dev team, though. You get those roles pretty much by asking for them and being willing to do the work, which is why esotericist has merge rights and I'm a moderator. I don't trust myself with merge rights and esotericist doesn't want to deal with moderation issues.

Game focus and direction

Question: Why don't you focus more on fun rather than realism?

(by I-am-erk, lore lead)

First, this is a false conflict. Realism and fun are not opposites. Requiring you to take HP damage to boil water would be less realistic, and also less fun. Having NPCs that make good tactical choices on their own would be more realistic, and more fun.

Second, realism is not the focus of this game. The focus of this game is to make something that feels like it could happen. The word for that is verisimilitude. A lot of the time, realism and verisimilitude are the same, but not always. We're happy to sacrifice detail to improve gameplay (see FMS entry on pooping) but we will usually accept contributions that improve verisimilitude. A key factor to consider is that we do not want do this at the expense of increasing micromanagement.

Finally, remember that your experience is not everyone's. Contributors consistently design and create complex and intricate simulations of survival elements because they want to play that. They get merged to the project because the devs like them. You, personally, disagreeing with this decision does not mean that fun was sacrificed, because all the people programming and merging these systems feel that it is more fun with them in the game.

Launchers, mod packs, and optional content

The (3rd-party) Launchers

Question: What's with the 'CDDA Game Launcher' not working?

Some people, playing on Windows, use a launcher called the 'CDDA Game Launcher' to update CDDA and mods and to start this game. There are also offshoots, "Catapult", "Kitten", and probably others. (The original CDDA Game Launcher by remyroy ceased to be maintained sometime after the 0.F release.) These launchers are not maintained by the CleverRaven team (the senior developers for CDDA and authors of this FAQ) and is generally not used by them. So there's not much that the senior developers can say about it.

If you're using the 'CDDA Game Launcher' and it's generating errors (which it often does), your best recourse is report the bugs and request technical assistance at the repository or source where you got it. Support for the launchers cannot be provided here, in any repository maintained by CleverRaven. We simply didn't make them.

Question: What's with my anti-virus program saying that the 'CDDA Game Launcher' is a virus or trojan?

Some Windows anti-virus programs will report the launcher as a virus or trojan. As far as the senior developers can tell, those reports are completely incorrect and the launchers we know of are benign projects that do exactly what they say. Still, this is third-party software and we cannot promise they are safe or be held accountable if they are not.

Question: I used a launcher to update my mods, but now I'm getting errors when I run the game and people are telling me it's because my mods aren't up to date. What gives?

You should contact the repository or source where you got it. I don't use the launcher. But as I understand it, the launcher keeps a cache of 3rd-party mods that is irregularly updated at best. When you update your 3rd-party mods with the launcher, it grabs the updates from that cache, even if the mod's author has updated it more recently.

Question: So if the launcher isn't well supported, how can I update my game without using it?

To manually update your game while preserving saves and settings, download and install the latest experimental version, then copy your saves and settings folders to the new directory. If you have third-party mods installed, you should also download and install a version of those mods which supports your new version.

What happened to the Undead People Tileset?

Several tilesets (of which MSX++UndeadPeopleEdition was a notable example, and previously the default tileset of C:DDA) contained an unknown number of assets verified as originating with sources whose licenses did not allow their reuse in this context. Further, given a lot of the other tiles had unclear provenance, it couldn't be certain that there weren't other illegitimately acquired assets in those tilesets. Accordingly, in order to keep the project legal and legitimate, those tilesets were removed.

Additionally the maintainer of "dead people/undead people" tileset, SomeDeadGuy, was prone to loud, drunken, angry outbursts and generally was uncooperative with the dev team in attempts to work with him on getting the tileset into an acceptable state. This culminated in him demanding he be banned from all C:DDA team controlled resources, and he was. This occurred well after the tileset's removal, and is not in any way connected with the tileset's ongoing absence (although it does make the situation unlikely to change).

Some of the precursor tilesets to MSX++UndeadPeopleEdition have been cleansed of all known bad tiles, and have active maintainers who have committed to cleaning them up if any other tiles are discovered to have legal issues. As such, those tilesets (currently ChibiUltica and MshockXotto+) are being distributed by the project again.

Mods and Mod Packs

Question: Is there any mod you recommend from Kenan's mod-pack?

(by Uplifted Mom Bun and Crow)

The popular ‘modpacks’ in CDDA have issues. Their original purpose of having many 3rd party mods hosted in the same place, to be easily accessed and archived, and to be at least partially maintained to the point they can at least load was a great idea! Having stuff preserved is always good, and the above reasoning is sound. But issues arose:

1. ‘Modpack’ itself is misleading. They are repositories of mods you can pick from, but the way they’re advertised encourages visitors to enable everything and mod their game to death. That's fine if that’s what they want to do, but ‘to death’ is not an exaggeration here and encouraging people to mod the game to instability isn’t great practice. Some mods are flatly incompatible with another mod, and putting both of them in a modpack and implying that they should both be loaded at the same time only causes problems.
2. The ‘maintenance’ provided is minimal, just to the point they don’t cause boot errors on load. This is fine since you can’t expect one person to keep that many things up to date, but as systems change it falls apart. E.g. Kenan’s pack advertises having an ‘up to date’ version of Blaze Mod. But the stuff in that one that isn’t in the new, in-repo, Blaze Industries version of the mod was cut for a reason — primarily stability, but also for using hacky workarounds, or trying to implement stuff that doesn’t even work. Several mods are like this and have received no updates outside of band-aids for the launch errors. Attached to this, the packs ‘save’ a lot of old mods without any curation. Again, you can appreciate them saving things for legacy’s sake but those mods don’t work. Some of these mods are old versions of packaged mods, or obsolete Locations mods that have since been merged with core. Using a lot of these mods actively damages your game, by overwriting the clean core content with it’s buggier or incomplete older versions. For instance, the old Boats mod was merged in the game before 0.D released, and the design and implementation of vehicle engines has changed dramatically since 0.D. Using the old Boats mod with the old version of oars creates canoes that cannot move because their engine power is much too low.
3. The repositories are fine, from a data perspective. But recommending new players to blindly jump into them as Modpacks ends up diluting, damaging, and generally worsening the New Player Experience of CDDA.

Question: Why are some mods included with the game and others not? Why aren't there more mods that just add vanilla content? Which should I use?

(from Maddremor)

The thing with mods in CDDA that differs from most other (commercial) games is that there is no clear distinction between the developers and the community. If a modder were to make a good piece of content, there is no reason to not just include it into the base game. That's why there aren't really any mod that adds more vanilla style content.

See also the policy on mods distributed with the game. https://github.com/CleverRaven/Cataclysm-DDA/blob/master/doc/IN_REPO_MODS.md

Mods usually fall into three categories:

1. Mods that clash with the theme of CDDA (Magiclysm, My Sweet Cataclysm)
2. Mods that are of poor quality or otherwise half baked
3. Mods where the author does not want to have their content in the game for some reason. This is often because the mod author doesn't want to go through the normal submission process, but sometimes because the mod author has been banned from contributing, and are rarely because the mod content wouldn't be accepted in the game.

This is why I (as an otherwise avid mod user) recommend that new players don't overload their games by installing all the mods available, and thus essentially getting an incoherent mess of a game. There are two mods included with the default game (Rural Only Mapgen and Desert Mapgen) that are basically incompatible: the first limits map locations to rural cabins and farms, and the second prevents the map from generating the fields and forests necessary for rural cabins and farms. But people will blindly enable every mod and end up with a game world that doesn't generate any legal starting locations.

This does not mean that you should never mod your game, but that you should know what you are looking for when modding. A decent way of finding out how the game plays, and what you would like to tweak or add, is to play the vanilla CDDA for a bit.

Your character

Avatar

Question: Why does this FAQ use "your avatar" to refer to my player character/toon/survivor?

CDDA (and the gaming industry generally) doesn't have a great set of terms for the in game entity representing the person playing the game. The CDDA code base was really bad about this, with a `Character` class representing all human/mutant things in the game, a `player` class that was supposed to be the in game entity representing the person playing the game but in practice was just an enhanced `Character`, and an `NPC` class that was an enhanced `player` for game entities controlled by the computer's AI. This confusion of classes and terms meant it was possible to say things like "the player can't control `player` here because the keyboard is locked" and that was bad.

There is an ongoing effort to redefine the terms and classes:

• player is the person actually playing the game by interacting with the computer running the game
• `Character` contains all vaguely human creatures in the game. `Character`s are more complex than `monster`s in terms of memory foot print and game interactions.
• `avatar` is the in-game representation of the player. It's an enhanced `Character` with user interface information.
• `NPC` is a computer controlled `Character`. It has AI routines instead of UI routines.

Time and Ticks

Question: How do ticks work? What does it mean to have 123 speed and a weapon with an attack cost of 167 ticks? How does this interact with monsters?

You get +100 (or whatever your speed is, but the default is 100) ticks at the start of each game turn (1 second). When you perform an action, you lose ticks equal to the move cost of the action. When your available ticks are 0 or less, your turn stops and monsters and NPCs can act. You get a turn again when your available ticks are positive, which may not be for several seconds if you perform an action costing several hundred ticks. I don't believe you can ever have more than your initial speed in ticks, so waiting on one turn does not let you build up a reserve of ticks so you can act twice as fast on a future turn. Also, waiting sets your available ticks to 0 and you refresh to your initial ticks on the next turn.

So if you're using a murdersaw with 180 move cost, and fighting a zombie that attacks at 100 moves per attack and has speed 70, it looks something like:

Turn	Your Ticks Start	End	Monster Ticks Start	End	Activity
1	100	-80	70	-30	You swing; zombie swings
2	20	-160	40	-60	You swing; zombie swings
3	-60	-60	10	-90	Zombie swings
4	40	-140	-20	-20	You swing
5	-40	-40	50	-50	Zombie swings
6	60	-120	20	-80	You swing; zombie swings
7	-20	-20	-10	-10	None
8	80	-100	60	-40	You swing; zombie swings
9	0	0	30	-70	Zombie swings
10	100	-80	0	0	You swing

So the zombie gets a few more strikes than you do over 10 seconds.

Mutations

Question: My mutant has wings. Why can't he fly?

Lots of animals (such as ostriches) have wings, but do not have the limb strength and wing span to generate sufficient aerodynamic lift to get their weight above ground. The largest flying birds weigh maybe 40 lbs and have huge wings. Your mutant weighs at least 3 times as much and does not have have enormously huge wings, so you can't fly.

Separately, Kevin has not been satisfied with the proposed user interface for personal flight, and doesn't like the proposed costs for personal flight. Being able to fly, in the current game, gives a mutant an amazing ability to avoid obstacles. Until Kevin is satisfied with the UI and trade-offs and challenges of being able to fly, mutants will not be allowed to fly.

CBMs

Question: Why was CBM power storage capped at 2,300 battery charges?

NOTE: Historical answer below, 32-bit support has largely been dropped as it's fallen below 1% of consumer PCs.

The new code limit for CBM power storage is influenced by a few things:

1. We want mJ accuracy on CBM power usage because a lot of CBMs would draw mW of power
2. We don't want to invoke 64-bit arithmetic unnecessarily, because CDDA does run on some 32-bit machines that are slow to start and get slower when they have to do 64-bit arithmetic.
3. 32-bit MAX_INT is 2^31-1, and MAX_INT mJ is ~2.2 kJ
4. 2.2 kJ is a reasonable approximation of the power you could store if you did stick reasonably efficient batteries just about everywhere in your body

What's the deal with this planned Exodii faction and CBMs? You can't be planning to lock CBMs away from an insanely long mission chain!

(Answer by i-am-erk, loremaster and mlangsdorf)

We can't plan to do that. CBMs are already locked away behind insanely long mission chains and are end game items for most players. What we are planning to do is make it easier to get CBMs earlier.

CDDA is set on Earth, and the game starts sometime in the next year (2022 at the time of writing). That means that common cybernetics shouldn't exist. As a partial solution to that, we're introducing the Exodii, a non-hostile of near-human interdimensional refugees and scavengers who have developed/scavenged CBMs some time in their past.

The Exodii are going to be easy to find, and eager to give out CBMs. They'll give you a Cable Charger CBM and a Power Storage CBM (installed, even!) basically for showing up, and simple CBMs for simple missions that you can complete in less than a day. Extremely useful CBMs like stat enhancers may take 2-3 additional missions, but a dedicated player could get them in a week or less.

You can still get CBMs by killing monsters in the new paradigm. For phase 1 you can then get them installed by the Exodii for cheap, and buy simple ones, getting more options by running quests. However as we go along you'll also be able to get other factions some CBM technology; at the very least, the Yrax, Hub01, Tacoma ranch, and the Free Merchants will all have equipment to install them, and you can help the Yrax or Hub-1 become a place to process and perhaps purchase CBMs as well. What exactly the Free Merchants do is undecided and probably you'll be able to influence it.

Rather than CBMs being another variation of "random loot you can pick up", we are making quests where you pit factions against each other and help influence their tech trees and faction relationships.

So I'm not going to be able to use CBMs unless I deal with NPCs?

You're going to be at least somewhat dependent on other people if you want to access the whole game. That's by design. Whether it's the Exodii or Yrax installing cybernetics in you, or Hub-01 helping you steal their tech and figure it out, cybernetics aren't something appropriate to try to do on your own.

Yes, we are aware of exceptional surgeons in dire circumstances that have simple surgeries on themselves. It's still not feasible to install a biochip in the middle of your spine. Nor can you rely on automated robotic surgeons to do the work - every person's nervous system is subtly different, and if you're trusting an unattended automated robotic surgeon to cut into your neck, you may find that you installed a CBM at the price of being able to move your arms.

Combat Options

Question: Can we select what point to target on an enemy with an attack like with VATS in Fallout?

The intended pace of combat in Cataclysm is very fast, because the game throws relatively large numbers of enemies at the player on a routine basis, as such micromanaging every attack, either at range or in melee is a non-starter.

We do have some plans for varying attack tactics related to setting a combat "goal" such as "takedown" vs "cripple" vs "damage", but this is something that would be infrequently adjusted based on the overall situation rather than requiring a decision with every attack.

See also, frequently made suggestions: https://github.com/CleverRaven/Cataclysm-DDA/blob/master/doc/FREQUENTLY_MADE_SUGGESTIONS.md#targeted-attacks-on-monster-body-parts-not-useful

Question: Can we select what martial arts techniques to trigger while fighting?

As outlined above, the pace of combat, especially in melee, is not amenable to micromanaging each attack.

Additionally, the design and balance of martial art styles is based on this random selection, and selecting the ideal technique each turn skews this balance, meaning we cannot consider technique selection as an optional feature either. Enabling it optionally would make micromanagement the optimal choice, therefore not optional at all.

Question: Can we curate what techniques are available to our character, either within a single style, or by mixing styles together?

While this partially addresses the micromanagement issues, this kind of feature has two major problems.

One is that the styles are designed and balanced as a unit, and like the above issue with selecting techniques to trigger manually, would require the styles to be overhauled and every technique to be balanced against every other technique, which is intractable.

The more problematic issue is that this would eliminate the tradeoffs between styles and result in "one true style" that is superior.

Items

Bows and Arrows

Question: Why do bows and arrows suck so much? Everyone knows a bow can propel an arrow through steel plate and kill a buffalo!

1. Historically, CDDA has based ranged weapon damage on the square root of energy in Joules. This is fine and gives us an acceptable curve with pistols clustering nicely around 20-25 damage, a jump to low caliber rifles around 40-50 and then some clustering as power goes up, and finally topping out at .50 BMG and other big rounds.
2. After the last 4 arrow reworks that failed for various reasons, Kevin got pissed and decided to whip them into something resembling shape. The senior devs did some research, looked up draw weights and delivered energy for a bunch of bows, checked hunting regulations to see the expectations for what an arrow fired from a hunting bow could be reasonably expected to kill, and such.
3. Arrows sucked because a high end bow is delivering maybe 200 J and that meant a base damage of 14.
4. Someone presented a well-researched and argued paper that said that arrows do damage out of proportion with their delivered energy, for various reasons dealing with how they are moderate energy, high momentum attacks compared to bullets being high energy, low momentum attacks. The senior devs reflected on this paper and concluded that the pure energy model worked okay for bullets but poorly for arrows.
5. Kevin did some more research and concluded (basically correctly AFAICT) that arrows cause serious injury by two methods: incapacitation after penetrating a vital organ and blood loss. An arrow needs to penetrate reasonably deep to hit vital organs, and arrows don't penetrate deep enough against things that are well armored or really big or whatever. Arrows can still cause blood loss on a shallow wound.
6. After some experimentation, Kevin came up with the current low damage, high critical hit models which matched his expectations from his research. You can kill a feral hog with an arrow, but you either need to get a precise shot to the vitals or wait for it to bleed out.

Now at this point, something like half the player community doesn't like the arrow solution that Kevin came up with. But telling the rest of the senior devs isn't helpful. You need to review Kevin's research and convince him that things need to changed. Otherwise, "[Kevin] will take great pleasure in only ever changing minor issues around the periphery of those complaints." (that's a direct quote from a DM discussing this FAQ answer.)

Furthermore, the senior developers have talked to people who are obsessives on the subject of historical armor and done some research. Actual English war bows with 150+ lb draw weights and 150+ Joules of delivered energy couldn't reliably pierce military grade chain mail armor, much less actual steel plate. A hobbyist bow made from random pieces of unseasoned wood and drawn out to maybe 80 lbs is going to do worse. The way that arrows completely fail in the presence of even mild amounts of armor is intentional. It may be possible to convince the developers that they're wrong about this, but it's going to be difficult and require a lot of research and reliable sources.

Question: Why does it take so much strength to use the good bows? Historical English archers could not have been Olympic bodybuilders!

The ''Mary Rose'' was an English warship that sunk in 1545 and salvaged in the 1980s. Preserved English warbows were recovered from the wreck, and the average draw strength of those bows was upwards of 150 lbs. So yes, historical English archers could more or less curl 75 lbs with each arm.

This situation also runs up against a lack of nuance in the stats system, your character has a single strength score which is applied to everything, meaning they are a pure generalist as far as physical fitness is concerned. Historical English archers did not have a uniform level of fitness, they intensively trained just the muscle groups necessary for firing a very heavy bow, and were not necessarily world class in any other areas. We have some boosts to effective strength based on archery proficiencies and are interested in adding more, but the requirement that very heavy bows require apparently excessive amounts of strength to fire is not going away.

Question: Why does the compound greatbow do less damage than the modern compound hunting bow? The greatbow has a strength requirement of 15, the hunting bow only requires 11!

The amount of energy a bow delivers to an arrow depends on a lot of factors, but the two most important ones are the strength of the bow and the efficiency of the bow design. The efficiency depends a lot on the materials the bow is made from. The compound hunting bow is made from modern fiberglass, which is a wonder material compared to any natural wood, and can bend farther with thinner limbs than a wooden bow, which means it has really good efficiency. Meanwhile the compound greatbow is made of random pieces of wood, and the limbs are much heavier than the hunting bow's limbs, and more of the bow's stored energy is spent just moving those limbs instead of being efficiently passed to the arrow.

If your avatar could make a compound greatbow out of fiberglass using modern engineering and manufacturing, it'd be a portable cannon. But the compound greatbow is made out of wood in a shack in the middle of swamp, and it's just not that impressive.

Question: Why do crossbows suck so much? They should be putting bolts through steel plate, and they're outperformed by modern hunting bows!

See the previous answer for a general discussion of efficiency. As it turns out, steel crossbows built to medieval designs are really inefficient: those steel limbs take a huge amount of energy to move, and the actual energy delivered to the bolt is really low. Modern compound crossbows are pretty good. Also, someone could submit a PR for a better designed steel crossbow item and fabrication recipe, and that crossbow would be more efficient and firing bolts with higher damage.

Books

Question: What do the book colors mean?

(by LaSagnyanFerret)

Book colors:

• Red = You haven't read it at all.
• Blue = You can read to increase your skills from it (or learn & level spells in the case of Magiclysm spellbooks).
• Pink = You do not have the necessary skills to read to increase your skills from it.
• Yellow = The book cannot be read to increase your skills, but has unlearned recipes.
• Grey = You cannot read to increase skills (or spells for Magiclysm spellbooks), and no unmemorized recipes(or spells) remain.

Book recipe colors:

• Brown = You do not have the primary skill requirement to craft that item using the book.
• Grey = You can craft the item using the book. The book must be close by or in your inventory to do this.
• White = You already know the recipe, and do not need the book to craft it.

Guns

Question: What do the gun colors mean?

(by XygenSS_)

Gun colors

• Green = the gun has available loose ammo, or a filled external magazine, in your avatar's inventory
• Red = the gun doesn't have a filled external magazine at hand, but there is a compatible empty magazine in your avatar's inventory
• Gray = the gun has no compatible ammo or magazine in your inventory

Magazine colors

• green = there is a compatible gun and compatible ammo in your avatar's inventory
• red = there is a compatible gun but no matching ammo, or compatible ammo but no matching gun, in your avatar's inventory
• gray = no compatible gun or ammo is in your avatar's inventory

Ammunition colors

• green = there is a compatible gun in your avatar's inventory
• red = there is a compatible magazine, but no matching gun, in your avatar's inventory
• gray = no compatible gun or magazine is in your avatar's inventory

Maps and the Reality Bubble

Map Terms

Question: What's an overmap terrain tile and overmap buffer?

1. The local map is main map that your avatar moves around. Each square of movement is called a "map square" and that's the smallest unit of map terrain that CDDA currently supports.
2. The area map that comes up when you hit `M` by default is the "overmap".
3. Each square of movement on the over is an "overmap terrain tile" and covers an area of 24x24 map squares.
4. Overmap terrain tiles are created and stored in "overmap buffers" of 180x180 overmap terrain tiles. Unique locations like Hub-01 or the Refugee Center are only unique to the local overmap buffer.
5. All of the overmap buffers in a single game world are stored in the "overmap", which is currently the largest unit of map terrain that CDDA supports. There are some plans to create a larger storage unit (possibly the "universe") to allow swapping between two different overmaps to allow for dimensional travel.

The Reality Bubble

Question: What's the reality bubble? How big is it? How can I make it bigger?

1. At any time, the CDDA game engine only loads and simulates the overmap terrain tile that your avatar is currently at, as well as two additional overmap terrain tiles in every direction for a 5x5 square of overmap terrain tiles or 120 map squares. This is the "reality bubble". Things outside the reality bubble generally don't exist and can't move or interact with the game. As your avatar moves around the local map, overamp terrain tiles are unloaded from the reality bubble and saved behind you, and new overmap terrain tiles are loaded or created into the reality bubble.
2. The size of the reality bubble is fixed when CDDA is created. If you can compile the game yourself, you can change the MAPSIZE constant to get a larger reality bubble. The current size of the reality bubble was chosen because there is a huge amount of data associated with the reality bubble and the size of that data increases with the square of MAPSIZE. CDDA intentionally supports some fairly old and low memory systems, but if you have a new and fast computer with a lot of memory, you can try increasing that number. This is not well tested.
3. A few things are simulated outside of reality bubble, such as horde movement. Many things, including vehicle power production and drain, food rot, plant growth, and animal reproduction, are "caught up" for elapsed time when loaded into the reality bubble.
4. Long term, there is a plan to increase the size of the reality bubble for everyone. Unfortunately, this is a complicated technical question that is going to require the attention of many senior developers working together over an extended period.

Z-levels

Question: What's a z-level? Why did the option to disable z-levels get removed?

The reality bubble is divided into vertical levels called z-levels. Each z-level is the floor of a building (roughly 14 ft or 4 m tall). There are 21 z-levels in the reality bubble, 11 above ground (including the ground level or z-level 0) and 10 below ground. The many z-levels contribute to the large size of the memory associated with reality bubble.

In versions 0.E and earlier, it was possible to disable z-levels. With z-levels disabled, the reality bubble only included the z-level the avatar was currently at - things on different levels ceased to exist. It was literally possible to escape zombies by running up or down a set of stairs. Disabling z-levels was a popular option for players on low performance computers, since the computer might have to only simulate a few monsters and NPCs on the current z-level instead of many more spread across 21 z-levels. This option was removed for the 0.F release.

A new feature for 0.F is ground vehicle ramps, which allow ground vehicles to move from one z-level to another by driving up or down a ramp. The design of ground vehicle ramps requires that z-levels be enabled, and does or is going to enable other gameplay changes like boats that can pass under ramps, vehicles with 2 z-levels such as double-decker busses, and elevated terrain such as hills. Extensive performance tuning was done by expert developers before the release of 0.F, and in general 0.F should perform faster with z-levels enabled than 0.E does without z-levels.

Zombie Hordes

Question: What is the wandering hordes setting and how does it work? What happened to the "wander spawns" setting?

(from esoterist)

The "Wander Spawns" setting was renamed "Wandering Hordes".

Hordes are the things that show up in the overmap overlays as a z or Z, with lowercase indicating a small number of zombies (between 3 and 6), and a big Z meaning more than 6 (up to potentially hundreds). Hordes smaller than 3 zombies do not show up on the overmap, but still exist.

Hordes can form either when zombies leave the reality bubble, or spontaneously during turns. Hordes can pull zombies from an unloaded overmap tile into themselves while on that overmap tile, although it will mostly only pull zombies in exterior areas (and a much smaller percentage of zombies in interior areas). Hordes exist and move outside of the reality bubble.

Over time, hordes can combine and split. They can move according to two primary algorithms, selected when the horde forms (including when hordes combine or split). They have no concept of obstacles, and will move through and into any overmap tile, including water or buildings. Hordes can be slowed by terrain (e.g. forests), but not stopped. The two primary horde behaviors are "navigate towards closest city center" (effectively, city nameplates) and "randomly wander".

Hordes can be attracted to sound, but sound only impacts hordes very briefly before they go back to their previous behaviors, so getting a nearby horde to chase you generally requires constant sound. Also over time, hordes can drop zombies into the reality bubble when positioned appropriately, generally when the horde is on a nearby overmap tile to the player.

Note: This is not how the senior devs want hordes to work, it's just an old legacy 'works for now' system. The plan is for something more nuanced that does in fact properly understand obstacles, barriers, and sometimes does things that can be mistaken for active intelligence. The gap in desired behavior vs current behavior (and the fact zombies will happily teleport through walls in the current incarnation) is why the setting defaults to "off".

Question: Do zombie masters have any effect on how hordes move?

Not at this time. Future horde logic will let lieutenant tier enemies (such as zombie masters) organize and command zombies, but it is not currently implemented.

Monsters

Zombie Evolution

Question: How does zombie evolution work?

Each zombies has half_life field that influences when they evolve, and a list of possible new zombies they can evolve into. 50% of zombies will change to their first upgrade within evolution scaling factor * half_life days, but each zombie type has a separate evolution timer. When a monster is created and it can upgrade, it flips a coin to see if it will upgrade within the first cycle. If it does, it uses a linear random number generator to pick a day within that cycle and records that day. If not, it flips another coin to see if it will upgrade in the second cycle and repeats the process. After 5 coin flips, the monster gives up and will never upgrade. When a monster is loaded onto a map, it checks if the current day is greater than its upgrade day, and if it is, it upgrades (and becomes a newly created monster than repeats the process of checking if it can upgrade).

If you're playing at the default evolution rate of 4, half of the skeletons will become skeletal brutes within 60 days, but it's a linear chance within that range. So of a population of 100 skeletons on day 1, you'd expect to see maybe 1 skeletal brute, but you could get 0 or 3. But zombies and tough zombies have a half-life of 14, and would get 50% evolution within 56 days, and zombie firemen don't evolve at all.

As a further example of how monster evolution works, say there are 4 types of monsters: squires, knights, lords, and paladins. (These are hypothetical monsters for this example and don't exist in game.) Squires upgrade into knights on a 28 day halflife, and knights involve lords on a 42 day halflife or paladins on a 42 day halflife with a 14 day spacer. This is the population density of the various types over time:

Day	squires	knights	lords	paladins
0	100.0%	0.0%	0.0%	0.0%
14	75.45%	24.55%	0.0%	0.0%
28	50.85%	49.15%	0.0%	0.0%
42	37.82%	62.18%	0.0%	0.0%
56	24.67%	73.78%	1.55%	0.0%
70	18.59%	74.22%	6.95%	0.24%
84	12.74%	70.43%	15.88%	0.95%
98	9.45%	61.81%	26.83%	1.91%
112	6.28%	52.62%	37.68%	3.42%
126	4.66%	42.78%	47.92%	4.64%
140	3.09%	34.79%	56.25%	5.87%
154	3.09%	26.96%	63.06%	6.89%
168	3.09%	20.33%	68.9%	7.68%
182	3.09%	14.82%	73.64%	8.45%
196	3.09%	10.92%	77.07%	8.92%
210	3.09%	7.87%	79.7%	9.34%
224	3.09%	5.92%	81.34%	9.65%
238	3.09%	4.78%	82.29%	9.84%
252	3.09%	3.92%	82.98%	10.01%
266	3.09%	3.44%	83.42%	10.05%
280	3.09%	3.14%	83.67%	10.1%

This assumes no deaths, of course.

As an example of how evolution works in the game, these are the monsters I saw after spawning on a new world with default evolution (4), advancing time by 200 days, and then teleporting into a random city block:

• basic zombie types: 1 zombie child, 3 zombies, 1 skeleton, 1 tough zombie, 2 crawling zombies
• evolved zombie types: 1 hulking horror, 4 zombie hunters, 1 slavering biter, 1 shady zombie, 1 smoker zombie, 2 grappler zombies, 1 kevlar zombie, 1 shriekling, 1 corrosive zombies, 2 listener zombies, 1 skull zombie, 1 bloated zombie, 1 incandescent husk

Buildings

Powered Buildings

Question": Why doesn't CDDA have powered buildings like Bright Nights does?

(by RenechCDDA)

I am not aware of the specifics of Bright Nights' powered buildings, but CDDA has appliances which can form power grids spanning many tiles and be connected across z-levels, without the need for specific structures or even any building at all.

See also https://github.com/CleverRaven/Cataclysm-DDA/blob/master/doc/FREQUENTLY_MADE_SUGGESTIONS.md#short-range-power-transmission-scale-of-a-single-building-largely-implemented

Vehicles

Fuel Consumption

Question: How does vehicle fuel consumption work? What does "drain" mean and what units is it measured in?

All vehicle power values are measured in Watts. For Americans, a Watt is about 1/750th of a HP, so a motorcycle alternator with a drain of 740 W consumes 1 HP of motive power from the engine it is mounted on.

An engine's base fuel consumption is fixed, based on the engine size and the combustion efficiency of the engine style: electric motors are 90% efficiency, steam engines are 50%, diesel are around 40%, gasoline combustion are 35%, and gas turbines are 25%. For a given amount of engine power, divide the engine power by efficiency to determine the amount of power that needs to be supplied. Different fuels produce different amounts of energy per unit of fuel consumed, but around 30,000 J per mL is typical.

So a 50,000 W gas combustion engine (which is like a v2 twin) burns about 150,000 W of gasoline if it were going all out, which it doesn't.

Determining the amount of motive power an engine requires to do some action is tricky. For a vehicle driving at a steady speed, you divide drag deceleration (due to wind and vehicle weight) by the vehicle's acceleration at that speed to get a load, and multiple the load by the engine's maximum fuel consumption. At safe speed, a gasoline engine is at around 60% load, so that 50,000 W v2 would be consuming 90,000 W of gasoline. Which is also 90,000 J/s, and gasoline produces ~34,000 J/mL, or about 3 mL of gasoline per second.

Alternators consume a fixed power: 750 W for motorcycle alternators, 1,500 W for car alternators, and 2,250 W for truck alternators. Divide total alternator power by engine power to get engine load, as above, which can't be below 1% of the engine load - so running a motorcycle alternator on a 150,000 W 4-cylinder engine is inefficient. Otherwise, you can put all 3 normal alternators on a 0.4L lawnmower engine and those plus a 7.5 kW generator on a large 1-cylinder engine.

Vehicle collisions

Question: How do vehicles take damage in collision? How should I design a vehicle to minimize damage in collisions?

When a vehicle collides with something, damage occurs at the vehicle square where the collision happens. The damage is proportional to speed and mass of the colliding objects, and armor protects normally. Any non-armor parts on the colliding square may get damaged, starting with the frame part. Each part's damage resistance reduces the damage, which is then applied to the part's durability (HP) and if the part is reduced to 0 durability, the remaining damage continues on to other another part at the same location.

The original damage is then converted to "shock damage", which can affect every other square of the vehicle. Shock damage is divided by the square of the distance in squares from the collision square to the relevant vehicle square. Most armor does not protect against shock damage, but shock absorbers do, but only for the vehicle square with the shock absorber (not including the frame itself). Shock damage is applied equally to every part on a square, reduced for that part by the part's damage resistance. Shock damage that continues past a shock absorber is not reduced for the later tiles: shock absorbers protect only the vehicle square they are mounted on, and no other vehicle squares.

In testing, a shock absorber completely prevented damage to fragile components 1 square away from an impact at a low speed (20 mph) and didn't reduce the damage enough at a moderate speed (40 mph). So they help, but you still need to collide carefully.

Some vehicle parts such as rams, spikes, and shredders do extra damage to the thing the vehicle collides with if they're at the point of impact, and ram plates count as armor during the initial collision, though not for shock damage. Ram plates are easier to install than armor plating of the same type and are slightly tougher, so they're a good idea if you plan to slam into things a lot. However, repeated high speed collisions are going to damage your vehicle, no matter how tough it is. Lower speed collisions help reduce the damage.

Flight training and building aircraft

Question: Since my survivor can build an armored vehicle from scrap metal and learn to hack military computers in a few months, why can't my survivor learn to fly a helicopter without any instruction or build a new helicopter from scrap metal?

See also: https://github.com/CleverRaven/Cataclysm-DDA/blob/master/doc/FREQUENTLY_MADE_SUGGESTIONS.md#there-should-be-helicopter-flight-simulators-in-military-bases-so-we-can-learn-to-fly-helicopters-no-but-yes

(by mlangsdorf, the current vehicles maintainer)

1. The fact that you can do other unrealistic things in the game does not influence my decision or Kevin's decision to not let do the unrealistic thing of self-teaching yourself to fly without crashing or building an aircraft without extensive flight testing (and crashing).
2. I totally support the idea that you should be able to build your own aircraft, if you're willing to take the high risk of a structural or mechanical design flaw, miscalculated balance, improper part installation, or any of the other myriad things that cause test aircraft to crash when they're being test flown.
3. I have not written and do not plan to write the code to support test flights. But hey, if this is something you want to do and you know how to program, give me a shout and I'll be happy to mentor you.
4. I firmly believe that self-teaching yourself how to fly by playing 100+ hours of MSFS 8 on a private pilot's computer rig is a completely inadequate way of preparing for a private pilot's license. However, after the Cataclysm, it's probably your best option and it at least gives you a fair chance of not crashing the first time you encounter a power-on airflow stall.
5. I have not written and do not plan to write the code to support learning via playing MSFS. But hey, if this is something you want to do and you know how to program, give me a shout and I'll be happy to mentor you.
6. Military flight simulators are 1000x times as complex as MSFS8 and require significantly more infrastructure and power. They are not a feasible solution for your learning-to-fly-after-the-Cataclysm needs to so please stop mentioning.
7. If you really don't like my ideas, you're welcome to convince Kevin that you'd be a better vehicle maintainer than I am and then you can decide how flying vehicle design and repair should work. But failing that, these are my general requirements for a general solution.

I tried to get a private pilot's license as a teenager, and I'm familiar with the requirements and challenges of flying a small plane. My brother was also a Power and Airframes licensed helicopter mechanic for 20 years, and would not shut up about it, so I know a little about the mechanic side of maintaining helicopters. Finally, as part of researching the topic of untrained experimenters building aircraft, I've read up on the experiences of the early aircraft pioneers like the Wright brothers, Sikorsky, Voight, etc. They all crashed, a lot, often for extremely surprising reasons, while learning to fly and learning to design and build their own aircraft.

Alternators and Foot Pedals

Question: I was reading a guide and it said my avatar could put a truck alternator, a car alternator, and a motorbike alternator on a stationary bike and pedal while crafting and generate plenty of electrical power for my base. But I tried that and my avatar can't do that at all! What's going on?

(by mlangsdorf, the current vehicles maintainer)

• On current (0.E+) experimentals and in 0.F or later stable versions, alternators draw 75 W, 746 W, 1492 W, 2238 W, or 10444 W, with draw increasing in size from bicycle alternator to 7.5 kW generator.
• Foot pedals provide 360 W + 60 W per point of strength over 8.

So if you're less than ST 15 and using anything other than a bicycle alternator, you're not going to be able to move the pedals against the resistance of the alternator. (You need ST 39+ to crank a motorcycle alternator without need to worry about immediately passing out from the effort, but that's a separate concern.)

If you're playing on 0.E, I think it's still possible to use foot pedals to power a car alternator, but since humans obviously don't produce 2 HP on bicycle pedals, I went and fixed that for 0.F.

Vehicle Design Formula

Question: What's the maximum amount of vehicle weight I can move with the engine in my vehicle?

(by mlangsdorf, the current vehicles maintainer)

Vehicle speed and acceleration is governed by a complicated set of equations, and though there's a simple answer to the question, there's not a good answer.

For a vehicle to move, it more or less needs to have an acceleration of 4 mph/s on pavement from a speed of 0 mph. As a rule of thumb, an engine can do that to a maximum weight (in lbs) of the engine's power (in Watts), or half that for people who prefer kilograms. This is the maximum weight the vehicle can move, but the top speed might only be 10 or 15 mph with an equally low safe speed. So you probably want to put in a larger engine, but determining how large an engine depends on your desired speed and acceleration, the aerodynamic profile of your vehicle, and the number and types of the wheels.

At any rate, here's the maximum weight that various engines and motors can move:

Engine Type	Engine Power	Max Weight (lbs)	Max Weight (kgs)
Foot Pedals	360	360	163
Tiny Electric Motor	800	800	370
Small 1 cylinder engine	3,730	3,730	1,700
Small Electric Motor	7,040	7,040	3,200
Electric Motor	36,000	36,000	16,300
Inline 4 cylinder engine	93,250	93,250	42,300
Large Electric Motor	150,000	150,000	68,000
v8 engine	2,424,250	2,424,250	1,100,000

The table makes it clear that even tiny motors and engines can potentially move ridiculous loads (16 tons for the basic electric motor!) But moving a vehicle at a reasonable clip requires a larger motor or engine than the minimum.

Question: What's the maximum amount of vehicle weight a boat hull can float? Is there any difference in how much the different types of hulls can float?

(by mlangsdorf, the current vehicles maintainer)

Boat hulls don't have an flotation rating. Instead, the percentage of the vehicle's squares that have a boat hull is the vehicle's coverage, which is roughly a measure of how much of a boat the vehicle is, and influences the height of the vehicle's water tight sides. The vehicle's mass displaces a volume of water, and if the height of that displacement (the vehicle's draft) is less than the height of the water tight sides, the vehicle floats. If not, the water pours in over the sides and the vehicle is destroyed if enters deep water.

Because of that, there's no difference in how much the different hulls can float. The different hulls have different durability and ease of repair. However, because some hulls are lighter than others, the overall vehicle weighs less and displaces less, and that can have a minor effect on draft. This is more pronouncement for small, light vehicles like canoes.

To a very rough approximation, a vehicle can float if it weighs less than 500 lbs * width in tiles * height in tiles * coverage - somewhat more for vehicles with close to 100% coverage, and about half that for vehicles with around 10% coverage.

Here's a table of some common areas (width in tiles * height in tiles), coverage percentages, and the maximum weight in pounds to have the vehicle float:

Area/Coverage	100%	80%	60%	40%	20%	10%	Sample vehicle
3	2,400	1680	1,080	600	240	105	Bicycle
6	4,800	3360	2,160	1,200	480	210	Golf Cart
8	6,400	4480	2,880	1,600	640	280	Large Golf Cart
16	12,800	8,960	5,760	3,200	1,280	560	Beetle
20	16,000	11,200	7,200	4,000	1,600	700	Sedan
30	24,000	16,800	10,800	6,000	2,400	1,050	SUV
40	32,000	22,400	14,400	8,000	3,200	1,400	Security Van
132	105,600	73,920	47,520	26,400	10,560	4,620	Huge Tank

On the reasons that tanks don't tend to float very well in CDDA is that are huge and heavy, but treads compete with boat hulls in the under slot and therefore tanks usually have low coverage. At 60% coverage, many tank designs will barely float.