Sleep

Sleeping restores fatigue and heals your wounds, so it's something you might want to do regularly.

Being under the effect of stimulants (coffee, Adderall, cocaine, etc) will make sleeping very difficult. You can consume those kind of items to purposely delay the need of sleeping.

Consuming Ambien, Cough syrup or Poppy sleep will increase your fatigue, and therefore help you fall asleep faster.

Lying down

The process of lying down in order to sleep.

To successfully sleep you'll need to reach a sleepiness above zero. That variable is checked when lying down, and it takes all these factors into consideration:

Penalties

• Suffering from sleeping pill dependence reduces it by 4.
• Having the Insomniac trait reduces it by 12.
• Being under stimulants will reduce it by double of current stim level for insomniac and the value itself for everyone else.
• Having fatigue below Tired (192 fatigue), reduces it by 1/4 of the value below 192.

Bonuses

• Having the Accomplished Sleeper trait increases it by 24.
• Having the Practiced Sleeper mutation increases it by 40.
• Being over a bed increases it by 5.
• Being over a vehicle bed, makeshift bed, cot or sofa increases it by 4.
• Being over a vehicle seat, extended rollmat, fur rollmat, arm chair or improvised shelter increases it by 3.
• Being over a straw bed, hay or tatami increases it by 2.
• Being over a chair, bench, floor, waxed floor, red carpet, yellow carpet, green carpet or purple carpet increases it by 1.
• Being in any other kind of terrain will decrease it by the current movement cost of the terrain type.
• If your level of fatigue is above Tired (192 fatigue), it will be increased by 1/16 of the value above 192.
• Chloromorphosis mutation increases it by 10 when on dirt, pit, mound of dirt, and shallow pit or by 5 grass, as long as there is no furniture on that tile, but can't sleep anywhere else.
• Spider threshold (also called Arachnid), Web Spinner or Web Weaver mutations increases it by 10 when in web of at least 10 thickness, but can't sleep anywhere else.
• Web Walker mutation increases it by 3 when in web of at least 3 thickness.
• Shell mutation increases it by 4 when in shell.

Sleepiness will also be increased or decreased randomly by a small amount (+/-8) each time this check is done.

You can't sleep under the effects of meth, having to wait until it wears off completely.

If sleepiness is above zero you'll start sleeping ("You fall asleep."), otherwise you'll stand up again ("You try to sleep, but can't...).

In addition to being sufficiently tired, you also need a comfortable enough temperature. The more bed-like your spot is, the more heat will be provided by it. This bonus heat will be used intelligently - it won't heat you above optimal temperature. It can't be used to cool down if it ends up negative.

• Furniture:
  • Bed (1000)
  • Makeshift bed, arm chair, sofa (all 500)
  • Vehicle bed (300)
  • Vehicle bed & seat (250)
  • Vehicle seat (200)
  • Straw bed (200)
  • Fur rollmat, hay (all 0)
  • Mutations that grant thick fur ensure "furniture heat" doesn't drop below 0
  • Cot, improvised shelter, tatami (all -500)
  • Rollmat (-1000)
  • Chair, bench (-1500)
  • Everything else (-2000)
• Any torso and leg clothing with volume > 0.25 liters lying on the tile or located in vehicle cargo will help with heating: 60 * warmth * volume / 2.5 liters (will heat up all body, not just relevant parts)
• Mutations that give you fur will provide both the regular "clothing" warmth (regardless of if you want it or not) and this special sleep warmth that can only help

To compare those temperature values with clothing "warmth" values, divide by 60 (when it's too cold) or 30 (when too hot). When in doubt, drop any torso or leg clothing with volume >9.

Cooling down is harder. First off (obviously) remove warm clothing. Second, don't lie in the sun: +1000 and +500 for sunny and clear weather respectively. If it still isn't enough, skip few meals before going to sleep (-hunger/6).

Sleeping

Reduces fatigue and heals all body parts. Hunger and thirst increase more slowly when sleeping. Your sight range will be reduced to zero (simulating closed eyes).

The amount of healing you get depends on a few factors:

• Your current health.
• Fast Healer, Very Fast Healer and Regeneration increase the speed of healing.
• Rapid Metabolism increases speed of healing.
• Slow Healer, Poor Healer, Imperceptive Healer lower speed of healing.
• If you have an HP-reducing mutation like Flimsy, Frail, or Fragile you heal slower, but only because your relative HP is lower. 10% of 80 is less than 10% of 100, so you gain less total HP in a given time.
• Broken limbs do not heal until mended.

You'll wake up when:

• Your fatigue is between 0 and -20 ("Fully rested.").
• There's a light source (such as the sun) and you've rested for a while ("It's too bright to sleep.").
• Your body temperature is low/high ("It's too cold/hot to sleep.").
• You cough - 1/10 chance if it's regular coughing (like from common cold), 1/3 if it can harm you (like from heavy smoke)
• You hear a sound (sound volume > sound distance to you). Effective volume is lowered by 3d15 if you have Heavy Sleeper.
• Your alarm beeps. Alarm is equivalent to sound of volume 12 (20 if from the Internal Chronometer bionic) going off at your location. If that doesn't wake you up, alarm will keep repeating every 10 minutes until you wake up.
• Your pain counter increases.
  • This probably means player is being attacked but it can also be Acidic Discharge or Electrical Discharge.
  • Deadened mutation cancels this - you can pretty much be eaten by a zombie if asleep. Sleep responsibly!