Hideout Facility Blueprints and a Supply Inventory

First was the valuable find from the metal cabinet.

When Yu Yuan took the blueprints out of his backpack, the Virtual Light Screen displayed information about them.

[On the Application of Passive Geothermal Ventilation Ducts in Underground and Energy-Efficient Buildings]

Quality: Rare

Description: Can optimize a Hideout's ventilation duct structure and automatically regulate indoor temperature with almost no energy consumption. Auxiliary equipment can add dust and odor protection, backflow prevention, humidity control, and protection against extreme weather.

Function: Keeps an underground Hideout's indoor temperature steady at around 10–25°C. With auxiliary equipment, the temperature can be adjusted.

"These blueprints are pretty good!" Delight lit up Yu Yuan's eyes.

Automatic temperature regulation with almost no energy consumption...

Wasn't that basically natural air conditioning?

Add all those other features, and it was practically the perfect ventilation system for an underground Hideout.

Looking closer, he saw that every line of the Geothermal Ventilation Duct had been drawn in clear detail.

Several pipes buried deep underground connected the building to the surface. Technical terms and symbols marked different points, each accompanied by a detailed explanation.

In simple terms, a Geothermal Ventilation Duct was a natural ventilation system that used the soil's stable temperature to regulate the air.

At a depth of 1.5 to 3 meters, the ground stayed at a steady 10–15°C year-round. Air passing through buried pipes would therefore be heated or cooled by the soil.

The system relied on natural differences in air pressure. It needed no electrical equipment, so it consumed no power.

The blueprints also listed the advantages and disadvantages of pipes made from different materials, along with the trade-offs of different layouts: pipe length, burial depth, and serpentine versus straight arrangements.

Of course, they also specified details such as the air intake, outlet, and pipe gradient.

In particular, a slight gradient of just 1–2% would drain condensation into a drainage pit, preventing it from flowing back.

The level of detail was impressive.

Once those optimizations were complete, the underground building's temperature could be regulated naturally with zero energy consumption.

Adding suitable auxiliary equipment would give it even more functions.

A low-speed fan, for example, could control the airflow. Air filters or humidity-control devices would keep out dust and odors and remove moisture.

They could even improve temperature control.

The Virtual Light Screen once again asked whether he wanted to add the blueprints to the Optimization Path.

"Optimize it. Absolutely!"

Yu Yuan did not want to wait another moment. He immediately chose to add it to the Optimization Path.

The blueprints in his hand flickered faintly, then vanished.

[Hideout ventilation duct Optimization Path added. Check it for details!]

He opened [Survival] → [Facility Management Log] → [Ventilation Duct Construction List].

Sure enough, the [Geothermal Ventilation Duct] had appeared on the construction list. To Yu Yuan's embarrassment, though, he had to complete level-three [Ventilation] before he could build and upgrade to it.

He had not even built the most basic Single-Duct Vent yet.

Well, damn.

The technology he had acquired was too advanced for him to use right now.

What could he even say to that? Yu Yuan did not know whether to laugh or cry.

Still, it gave him something to work toward. He would make the Geothermal Ventilation Duct his short-term goal!

After sorting everything, he was left with three things he did not know what to make of.

A wallet, a hotel keycard, and a key ten centimeters long.

All three had come from Brother Biao.

The printing on the keycard had worn away until the name was illegible. He could only make out "XX Grand Hotel" and a logo resembling a bauhinia flower.

The room number on the back was still clear, though: Room 0813.

The key clearly was not an ordinary room key, either. After thinking it over, Yu Yuan put both away and picked up the wallet.

It was a woman's wallet, with a family photo inside. The man in the picture was not that ugly bastard Brother Biao.

He was a rather handsome man in his thirties.

Huh. Which poor soul had Brother Biao stolen this from?

Yu Yuan raised an eyebrow and leafed through the wallet with interest. It was clean inside, containing a neatly folded water bill and a few banknotes he had never seen before.

And several... condoms?

Yu Yuan blinked, momentarily stunned.

What was going on here?

With all the loot checked, the hotel keycard and key suggested there were supplies to be found.

Anything Brother Biao kept on him had to be valuable.

He just needed to find the hotel.

Next came upgrading the Hideout's facilities. Yu Yuan had kept the system's advice in mind: improving the Hideout as much as possible was his long-term goal.

To upgrade the Hideout door, he still needed three units of wood and two hinges. He already had enough screwdrivers and screws.

To build the Rest Area, he still needed a yoga mat. He had already gathered a lighter and old cloth.

For the Bathroom, he still lacked a bucket, but he had found a towel...

After listing the remaining Construction Supplies, he searched Taotao Cave. It did not take long for him to start cursing.

"Damn it, a bucket costs 200 Survival Points, and a yoga mat costs 500? Are they insane?" Even counting every last point, he had only 300 Survival Points. That was barely enough for a bucket.

Only an idiot would pay those prices!

But he soon noticed a pattern in the prices.

Manufactured and household goods were generally expensive. Natural materials such as wood, stone, and stream water, on the other hand, were reasonably priced.

A unit of wood or stone cost 5 Survival Points. A liter of clear stream water cost 20, while lake or river water cost just 10 per liter.

Yet a 500-milliliter bottle of drinking water shot up to 80 Survival Points.

Yu Yuan understood.

The prices depended on how hard the supplies were to obtain!

Manufactured and household goods could generally only be found in places where people had gathered, such as cities, villages, and factories. Those places were full of thugs, Refugees, and Scavengers. The danger was far greater, while the goods themselves were scarce.

Yu Yuan had fought Refugees and knew how dangerous they were. As for thugs armed with heavy weapons, being spotted by them meant death.

The harder supplies were to obtain, the more valuable they became.

Once he understood that, Yu Yuan's eyes lit up.

Looking at the enormous haul he had brought back tonight, he grinned.

"Scarcity is good! Taotao Cave doesn't just let people trade with Survival Points. They can barter, too!"

He got to work at once.

Before long, the player chat channel under [Social] was scrolling like mad.