The shelter is an upgradable feature of your campsite, located at the campsite's far-left end. The shelter has two purposes: sleeping and saving your game. When you sleep, you regain Health, and your Feed Lvl decreases at a slower rate than when you are awake.
When you initially find your campsite and repair the shelter, you'll find that it's nothing more than a makeshift tent. It is highly recommended that you Inspect your shelter before you use it to go to sleep. Inspecting the shelter will occasionally reveal a snake. If you don't Inspect the shelter and a snake is inside, the snake will bite you when you try to sleep, and you will lose some Health. If this happens, you will be kicked out of the shelter, at which point you should Inspect it to remove the snake. Inspecting the shelter also has the added benefit of awarding you some Experience Points.
When you sleep, you will occasionally be awoken by mosquitoes (follow the link for more information on dealing with these pests).
Upgrading your shelter: Edit
The primary benefit of upgrading your shelter is that each upgrade improves the rate at which you recover Health while sleeping. Each upgrade (there are two) also changes the appearance of your shelter and affords a secondary benefit:
The first upgrade to the shelter changes your shelter's appearance to that of a small house (more of a tent supported by exterior wooden panels). The secondary benefit of this upgrade is that it prevents snakes from entering the shelter. Therefore, you will no longer need to Inspect your shelter before sleeping. In fact, the option to Inspect the shelter will be removed from the game entirely. This can be a bit of a double-edged sword, because you can no longer repeatedly Inspect the shelter to gain Experience Points. Because the game offers plentiful sources of Experience Points, this is not a major inconvenience.
The second upgrade to the shelter is the final upgrade for this feature of the game. This upgrade changes the appearance of the shelter to that of a large house (a wooden shack, really). The secondary benefit of this upgrade is that it prevents mosquitoes from biting you while you sleep, so you will no longer be awoken by the pests. It also retains the secondary benefit of the first upgrade.
Using Your Shelter Edit
As mentioned above, the shelter has two purposes, and thus two uses: first, as a place for your character to sleep and regain Health. Second, it is where you save your game.
To use your shelter to sleep, approach the shelter until the Interaction Menu appears, then click on the Use icon or press the corresponding hotkey. Your character will disappear from view and animated Zs will start to float out of the shelter, representing that your character is asleep. While sleeping, your character will dream. These dreams are represented by text in thought bubbles that emerge from the shelter from time-to-time. If your Health is below 50%, the text will indicate that your character is having bad dreams/nightmares. For example, it might say, "Dreaming about falling." If your health is above 50%, the text will indicate that your character is having good dreams. For example, it might say, "Dreaming about playing video games." Neither bad dreams nor good dreams have any effect on gameplay.
The game will not allow you to use the shelter to sleep while zombies are nearby. "Nearby" meaning within the campsite or just outside of it. If you attempt to use the shelter while zombies are nearby, the game will give you a message that zombies are attacking your camp. If you get this message, it is recommended that you stop what you are doing and go repel the attack.
As you sleep, you will regain Health. Sleeping is the only way, other than by consuming food or crafted healing items, that you can regain Health. Sleeping has the benefit of costing no resources, but the drawback of taking time. Sleeping is not required by the game. Your character can go without sleep indefinitely, so long as you keep your Health up through other methods.
The rate at which you regain Health while sleeping depends on two factors: one, the upgrade level of your shelter and two, how many points you have invested in your Endurance stat. Of the two factors, the shelter's upgrade level appears to have the greater effect. A level 2 shelter appears to restore Health about twice as fast, and a level 3 shelter approximately three times as fast, as a level 1 shelter.
Saving Your Game Edit
Alone: Zombiewoods does not autosave! Therefore, it is imperative that you save your game manually, and do so frequently. To do this, go to your Shelter and, when the Interaction Menu appears, click on the Save icon, or press the corresponding hotkey.