Design of Fatigue and Hunger Fundamentally Flawed


I noticed there is some discussion already on the subject, but since my perspective on some of the issues is not identical and they have not been addressed yet, I thought to open up a separate topic.

Last night a played the infected scenario. While antibiotics are perhaps a little too rare, the first part i.e. getting the infection cured worked out just fine several times. It was actually pretty fun hunting for the drug. However, the recovery period makes no sense whatsoever. After sleeping it off, I was so deep in exhaustion (fatigue ~7000) it’d have taken weeks to sleep it off. Since you keep falling asleep every couple of tiles, this is pretty much death sentence.

Fatigue just doesn’t work like this. Once your neurotransmitters (and other relevant chemical stores) are depleted, it’s physiologically impossible to get any more tired. No matter how long you stay up, a couple nights of good sleep restore an otherwise healthy person to working condition. Sure there are people sleeping for weeks or months in hospitals, but it’s either due to the infection remaining uncured or entirely other mechanisms such as brain damage. Having your arm infected for a day does not cause that.

The trivial fix of capping fatigue at 1000 would work out pretty well. Still it doesn’t make much sense that during your recovery period from an infection you keep getting worse, not better. Should be the other way around.

As for hunger, the problems are not as critical, but still annoying as hell. After a couple of days of fasting and then having eaten a number of good meals, I still get constantly bombarded by the “your stomach feels so empty” warning. This makes physiologically no sense either. When you get less than optimal amount of nutrition, you lose weight. Thankfully not everyone who has dieted a couple of kilograms off doesn’t feel constant craving in their stomach. Of course, during the diet, but not after it. You might be missing some key nutrients, but there is already a separate system in place to track those.

I know the messages are triggered by your energy reserves going below a fixed target amount and keep coming until you’ve fattened yourself up to that. This is not a good way of handling weight changes and hunger. Some people are just thin and may still be extremely muscular and fit. They just have a low fat percentage and thus lower reserve calories (as muscle tissue has less energy than fat). Definitely they don’t feel unnaturally hungry constantly.

Unlike for the fatigue issue, there is no easy fix for this. Just widening the acceptable range of stored calories does only so much. It’s questionable if tracking the long-term energy reserves of your body really makes the game more fun. If this is still to be done, muscle mass and reserve fat should be recorded separately. Losing muscles could maybe cause reduction of strength. This would require the addition of electric fat percentage measurement devices such as people have built in in their bathroom scales. Having more excess energy stored should allow you go on longer without food before you die. The warning spam and constant hunger every couple of hours are unacceptable.

Sorry for the wall of text, but these issues really need redesign badly. Whoever is responsible for these systems, please take another look at them. Make them physiologically more accurate or at least less frustrating.

Thanks, and Happy upcoming New Year.



capping fatigue

Maybe, that could work. Reworking infection recovery would probably be better.

Message about hunger

I don’t get your point. The message is just gameplay so that players have some idea about their energy storage, it could be displayed another way, or phrased another wway (“your stomach feels empty” is misleading because it’s not actually about an empty stomach) but it’s just flavour that’s not really part of the hunger simulation.

I guess you’re somewhat correct here. The frustration comes from having to see the misleading message constantly. Maybe changing it and reducing the frequency it appears would solve most of the problem. Phrasing it “you notice you’re a bit slim and could benefit from extra mass just in case of emergencies” and having it appear once per game day would be acceptable.

Still, it indicates that the underlying mechanism is not making much sense as it is and could definitely be improved. A set amount of required energy storage is not how people work.

As for your suggestion of redesigning the infection recovery I wholeheartedly agree =)



A set amount if required energy storage is not how people work.

The messsage start appearing when you are below 80% of your healthy calorie storage, that’s as good a threshold as any.

Maybe the problem is in how the healthy calorie storage is determined. A tiny woman and a huge man have vastly different calorie consumption and recommended calorie storage. Still they might both be extremely good at surviving and even have the same potential to tolerate food deprivation.

But yea, it’s not such a big problem. If we assume all survivors and identical in size and base calorie consumption, it’s just more about making the message sensible and perhaps considering in what way should a person become aware of the status of their energy storages.

Everyone starts at 1.75m, healthy calorie and calorie consumption is based on BMI, look at the code and the stomach PR if you want to know more. Changing the message is trivial, I don’t know if anyone is interested in working on it though.

Ah, have to admit that I actually didn’t know that. This is good enough for me. I’ll take a look bit later and see the code. I’m sure I can change the string but I’ll have to also locate the logic determining how often it is displayed.

For the infection recovery it’s better someone more experienced in coding handles it. I’ve been MD for 20 years with my speciality in immunology and biochemistry, so I’ll happily help with the theory if you think it’s beneficial. However, it’s been ages since I’ve actually coded anything, so I hope we can find some skilled person interested in tackling the issue.

Ok. How about we do it like this:

  • Fatigue is capped at 1000 for reasons mentioned above.
  • The recovery time from an infection equals its duration only if it has gone to septic i.e. spread to your bloodstream (this could be the pus-filled state) – otherwise only the square root of it.
  • Additional fatigue during recovery is scaled by the remaining recovery time thus dwindling eventually to levels where you can actually recover overall fatigue by sleeping once you’re close to being well again.

And a bonus one:

Strong stimulants should immediately enhance your abilities and stamina no matter what allowing you to fight off a couple of zombies even when recovering. A good hit will make an almost dead person run for a while. There’s a reason why special forces carry amphetamine derivatives. Also, while the effect lasts, you shouldn’t fall asleep regardless of the fatigue level.


EDIT: Oh, and while I’m at it, a couple more possible ideas:

  • The ability to cut open an infected limb and locally treat it evacuating pus to improve chances of recovery. This would require some skill in first aid.
  • Intravenous antibiotics - while they are demanding to administer and very difficult to manufacture, they would work practically always and faster than oral antibiotics - just like in real life.
  • It might be worth considering to have antibiotics reduce the level of infection over time. If they and your immunosystem kill bacteria faster than they reproduce, it’d be a more realistic race rather than a random spot chance to qualitatively overcome the infection. This may be a bit too complicated to be worth it tho.
  • Do animal bites get infected or just the zombie ones? Not sure about this one, but if not, they definitely should. And come to think of it, wearing filthy clothing on wounded body parts should cause infections. And swimming in dirty water while having wounds. Too much realism or an interesting way to make first aid skill more meaningful?

Pardon me for clinging to this subject. I suppose I’m a bit partial. It’s just that I was annoyed with several of my characters dying to such ailments I personally would have had a good chance of healing even in the absence of antibiotics. For example, antiseptics being useless in treating pustulent infections seems very wrong. In reality surgical revision and mechanical disinfection of deep abscesses goes a damn long way toward saving people’s lives.

I put some serious thought in actually making the changes myself, but the threshold of participating for someone who has never really been involved in the project is quite high. While turning these ideas into useful metacode is not much of an effort at all, implementing them is another thing altogether. It’d require installing proper tools, familiarizing myself with the structure of the project, its working pipeline, a new syntax etc. I’m sorry to say I just don’t have the time and inclination to currently involve myself on such a level. However, someone with an intimate understanding of the game’s code could probably convert and apply such snippet as a matter of minutes.

I realize this is just a small aspect of the total gameplay and may not matter much to most gamers. Still it’s part of the core mechanics and deserves to be rationalized. If some dev here agrees with me and feels up to the task, please let me know. I’ll help out where I can.




This is an argument for a more nuanced fatigue model, not making the existing system pointless by capping it before serious symptoms occur.

If you understand the mechanisms here we need outlines of how it works in reality more than we need implementation details.

You took me by surprise there. I didn’t think going deeper in neurophysiology was an option, but very well. I’m excited =)

First, we have to separate physical fatigue from drowsiness. In exercise muscle tissue expends fuel storages, accumulates harmful metabolites and may suffer microtrauma. While much of the recovery from these happens in minutes, they can reduce your maximum strength up to a couple of days and cause pain during the regeneration.

Mental fatigue is significantly more complicated. I’ll omit the details about specific transmitters, but on a more general level there are a couple of points worth understanding for this purpose. As with muscles, toxic metabolites accumulate into brain during the day. Sleeping allows clearing these as well processing your experiences and building new pathways i.e. learning. However, normal drowsiness is not so much directly caused by such changes but is more related to the circadian rhythm. The simplified version is that since it is beneficial to sleep regularly, your internal clock induces the urge to catch some Zs in the evening. This is a relatively weak signal and can be overridden by simply choosing to stay awake.

With increasing sleep deprivation (exacerbated by possible infections) things start to change qualitatively. Further accumulation of harmful metabolites and changes in the levels of the neurotransmitters, receptor susceptibility and cell membrane permeability render the neurons unable to reliably receive, process and send signals. Symptoms include difficulty in the ability to concentrate, slowed cognition, memory problems, mood swings and reduced hand-eye-coordination. Learning becomes impaired as the new information cannot be understood and ordered properly.

After a couple of days of sleep deprivation microsleep starts to occur. The patient partly loses consciousness for a couple of second at a time as the brain tries to steal a little bit of sleep. I believe there is already a mechanic for this in place, so I won’t elaborate on in. After three days (this is the longest I’ve personally gone without sleeping) one begins to have problems expressing oneself coherently. Dream imagery starts to pour over into reality causing inappropriate or even paranoid associations and makes performing complex tasks extremely difficult. Still, even at this point an average person can choose to stay awake as long as they keep themselves busy with something.

From that point on less data exists. Healthy people have been documented to avoid sleeping for several weeks and individuals suffering from the rare familial insomnia even for months. At this stage a homeostasis is reached. No significant changes occur anymore. The toxic metabolites are flowing out at the rate they are generated and the brain becomes perpetually clouded by them. Hallucinations and psychoses have been reported for a fraction of the patients. Current consensus is that sleep deprivation is not fatal per se, but the widespread changes in energy metabolism can cause organ failure.

Then on to the recovery part. This homeostasis I mentioned is the real life “capping” of neural fatigue. Restoring proper balance takes a day of good quality sleep or two at most. Practically all patients regain full functionality at this point, barring some of the psychoses and may still be left traumatized by the events that caused the sleep deprivation in the first place. Much of the memories of the time spent awake, however, are at least partially lost and little learning is retained.

I’m not sure if this answers your request sufficiently, but I hope at least of some of this information will be useful in designing an improved fatigue system. I’m happy to answer any questions you might have.


It has been a while since my last reply, so I thought to ask whether my information about sleep and fatigue was useful. Also, since I didn’t cover illness related fatigue in any detail, it might be worth discussing.

While I said that traditional bacterial infection doesn’t cause excessive fatigue until it becomes systemic, we can of course make it anything that suits the game balance. It’s not like there was any lack of real life examples. Or we could even have several different kinds of infections. Maybe the zombies spread a different strain that normal animals or humans. At least to me personally it sounds like a fun idea, but then again I may be biased.

If you want to know what’s going on development wise I suggest checking out the github

I think it’s a useful outline, but as I’m trying to get the 0.E release out the door, it’s not something I have a lot of time to look into at the moment.