A night breeze slipped in through the window cracks, rustling the fuel list on the table. Chen Hao reached out and pressed down on the corner of the paper, glancing up at the window. It was already pitch black; the distant ruins looked like a jumble of crooked building blocks in the moonlight.

He rubbed the goosebumps on his arms, remembering how he'd been woken up by the cold wind last night. As he turned over, he heard a bang from the window; he got up and saw the latch was loose. He'd spent the night wrapped in a blanket, and thinking about it now, it still felt suffocating.

"Nana," he turned his head, "can you still access the building maintenance module?"

The robot stood in front of the terminal and lightly tapped the screen. "Okay. Which part would you like to view?"

"Doors and windows." Chen Hao stood up, walked to the oldest iron-framed window on the wall, and pushed it hard. The window frame wobbled twice, and the screws were almost coming out of the cement. "This thing is not only not windproof, it can also let rainwater into the house."

Nana walked over and scanned the window structure. "Currently, there are seventeen doors and windows in the base with sealing defects. The average indoor temperature in winter is 3.2 degrees Celsius higher than the outside temperature, and heat loss mainly comes from ventilation through gaps."

"So, half of the heating we're burning is going to feed outside?" Chen Hao grinned. "No wonder I always feel cold."

Susan, carrying a cup of hot water, stopped by the door upon hearing this. "You need the doors and windows fixed?"

“It’s not repair, it’s modification.” Chen Hao turned around. “Now that the tunnel is being dug smoothly and we have enough fuel, we need to get our living quarters sorted out, right? Otherwise, if it rains heavily one day and the electrical box gets flooded, nobody will be able to work.”

Susan didn't speak, but instead blew a puff of hot air into her eyes. "Where are the tools? The cutting machine is still in use to support the tunnel construction."

“I know.” Chen Hao waved his hand. “We won’t rush during the day. We’ll handle everything together after we finish work at night, doing it in sections. First, we’ll dismantle the old frames, then make the new ones, one batch at a time.”

Carl, carrying his toolbox, happened to pass by and, hearing the noise, peeked in. "You said you're working overtime tonight?"

"It's not considered overtime," Chen Hao laughed. "Just consider it a bit of fun for my nightlife."

“You said last time that nightlife was like stewed chicken with rice,” Carl put the wrench in the cabinet. “You ended up working until 2 a.m..”

“This time is different.” Chen Hao slammed his hand on the table. “This is for the sake of quality of life. None of you want to be woken up by the wind in the middle of the night, right?”

Nana suddenly spoke up: "If recycled materials are used, theoretically, zero-cost modification can be achieved. However, three issues need to be addressed: material strength, sealing performance, and processing feasibility."

“Speak like a human.” Karl scratched his head.

"The problem is that plastic is too brittle, wood is susceptible to moisture, and glass shatters with the slightest vibration," Chen Hao added. "Besides, we don't have any ready-made sealing strips, and we don't have enough adhesive either."

Susan leaned against the doorframe and took a sip of hot water. "What are you planning to use for the new windows?"

Nana brought up the interface, and three solutions appeared on the screen.

"Option A: Melt and cast waste plastic into boards and fit them with metal frames; Option B: Use multi-layer compressed wood chipboard with a waterproof membrane; Option C: Repair old aluminum alloy windows and add soft sealing strips."

Carl leaned closer to take a look. "A sounds cheap, but how long can plastic last? It'll melt in a fire."

“It won’t catch fire,” Nana said. “I will control the melting temperature and add flame retardant.”

“That won’t withstand strong winds either.” Susan shook her head. “Last typhoon ripped half of the warehouse roof off; this kind of material won’t hold up.”

"What about Plan B?" Chen Hao asked.

“There are too many materials.” Susan flipped through the notes. “The sawdust needs to be pressed into shape, the waterproof membrane needs to be found intact, and we also need adhesives. The process is more complicated than that of fuel rods.”

“Then let’s go with C.” Chen Hao pointed to the screen. “Repairing an old window is easier.”

“The problem is that the old window frames are severely deformed.” Nana showed a set of data: “Of the twelve existing aluminum alloy windows, nine cannot be closed, and all the sealing strips have aged and fallen off.”

“So we need to replace the sealing strip.” Chen Hao picked up a pen and drew a U-shape on the paper. “Just find a rubber tube and cut it open.”

“The rubber materials in the inventory have expired,” Nana said calmly. “Prolonged exposure has caused the molecular chains to break and lose their elasticity.”

The room was quiet for a few seconds.

"Does that mean we don't have any good materials?" Karl frowned.

"To be precise, it's a lack of sealing materials that combine weather resistance and processability," Nana added.

Chen Hao sat back down in his chair, staring at the ceiling. "Couldn't we find somewhere to pick up something useful? Like those PVC windows that are commonly used on construction sites?"

“It’s possible.” Nana pulled up the map. “There used to be building materials markets and renovation warehouses within a five-kilometer radius, but we haven’t confirmed any usable resources yet.”

"That means we can search for it." Chen Hao's eyes lit up.

“But we can’t move now,” Susan said immediately. “The tunneling progress has just stabilized, and fuel production is only just getting on track. What if something goes wrong if you take people out to find materials now?”

"I'm not going to fight," Chen Hao said, shrugging. "I'm just seeing if there's anything ready-made that I can bring back."

“The risks aren’t just outside.” Susan put down her cup. “You’re in charge. If you leave, the whole process will be thrown into chaos. And the search could take several days, delaying construction.”

Carl nodded. "She's right. If we come back empty-handed after three days without finding anything, morale will suffer."

Chen Hao stroked his chin and remained silent.

Nana suddenly said, "I suggest we make the door and window renovation a parallel project. In the early stages, the team should take stock of available materials and develop a dismantling and assembly process. Once the tunnel has been advanced to a safe area, we can then arrange a short search trip."

"So, you mean we should start by making preparations?" Chen Hao asked.

“Yes.” Nana nodded. “Including tool allocation, personnel division of labor, and timeline planning.”

Susan thought for a moment and said, "I can be in charge of materials management. But if we find that there is a shortage of key resources, we must prioritize the tunnel project."

"No problem," Chen Hao agreed. "This won't interfere with the main plot."

Carl sighed. "Then I'll spend two hours tonight checking if there are any usable plastic buckets left in the warehouse. We need raw materials for the molten metal."

“Okay.” Chen Hao smiled. “You do your research, Nana makes the list, and I’ll start drawing the renovation plans tomorrow.”

"You can draw?" Karl didn't believe it.

"I practiced by copying homework before," Chen Hao said seriously. "I can even trace function graphs, so drawing a window is nothing."

Susan couldn't help but chuckle, then immediately straightened her face. "Don't just talk the talk. If you're really going to do it, you need to show some results."

"Don't worry." Chen Hao stood up, walked to the window, and slammed the shaky old window shut. "By this time tomorrow, I'll make sure this window is completely draft-free."

Nana began compiling the material requirements list. Various parameters scrolled across the screen: wind pressure resistance rating, light transmittance, thermal conductivity...

Chen Hao stared at the window that was barely closed; the wind was still squeezing in from the edge, making a faint whistling sound.

He turned around and asked, "Nana, do you think we could get our hands on those double-glazed windows? I heard they're really good at keeping things warm."

“The database contains the relevant processes,” Nana replied, “but manufacturing requires vacuum equipment and special sealant, which is difficult to achieve under current conditions.”

"Then there isn't one." Chen Hao scratched his head.

“However,” Nana continued, “there is an alternative—using two layers of polycarbonate sheets with a gap in between. The air gap can act as insulation.”

"It sounds like a sandwich."

"Similar in structure."

"What about the materials?"

"Look for large, intact plastic sheets. They are commonly found on the backs of old greenhouses, carports, or billboards."

Chen Hao wrote it down. "I've seen plenty of billboards, but I don't know if they're still usable."

“An on-site assessment is required,” Nana said. “Slight aging does not affect the structural strength.”

Susan glanced at the time. "Let's leave it at that for now. Everyone get some rest early tonight. We'll start taking stock of the inventory first thing tomorrow morning to see just how much we actually have."

She turned and left.

Carl yawned. "I'm going to check the equipment."

Nana continued to enter data into the terminal.

Chen Hao stood there, looking at the preliminary plan that had just been printed out. The paper showed three combinations of materials, several key areas marked with red circles, and a line of small print that read: **Initial Goal—Close the doors and windows of the main hall and dormitory area**.

He picked up a pen and wrote down a new plan next to it:

Tomorrow's Actions

1. Count the number of usable plastic/metal frames.

2. Check if there are intact boards in the warehouse.

3. Test whether the small furnace can operate stably.

After he finished writing, he stuck the paper on the wall.

The wind blew against the window again, making a creaking sound.

Chen Hao walked over and stuffed the largest gap with a rag.

He returned to his seat and stared at the list of materials on the screen.

Nana said softly, "According to the analysis, the optimal path is to find abandoned agricultural greenhouses. Their covering materials are consistent with polycarbonate and they usually exist in large patches."

Where is the greenhouse?

"Approximately 3.2 kilometers to the northwest. Satellite images show that part of the structure has collapsed, but there are still obscured areas."

Chen Hao nodded without saying anything.

A few minutes later, Carl peeked out from outside the door. "There are a few large plastic barrels behind the warehouse, they don't look cracked."

"Keep it," Chen Hao said. "We'll use it for melting tomorrow."

Carl responded and left.

Nana closed the terminal. "Today's mission log has been archived. I suggest you take a break."

"Sit a while longer." Chen Hao leaned back in his chair. "I was thinking, it would be great if we could find one of those sliding windows with rails, so they'd be easy to open and close."

“It’s technically feasible,” Nana said. “If there is enough material for straight tracks, a simple sliding structure can be replicated.”

“The tracks…” Chen Hao murmured, “Can the legs of the iron-framed bed be disassembled and used?”

“Precision measurement is required,” Nana cautioned. “A deviation exceeding two millimeters can cause the device to jam.”

"Let's give it a try anyway." Chen Hao cheered up. "As long as we can close the windows tightly, everything else is minor."

He stood up and stretched his shoulders.

The wind outside grew stronger, causing the tin roof to vibrate slightly.

Chen Hao took one last look at the drafty window, then turned and walked towards the door.

Just as his hand touched the doorknob, Nana suddenly said:

"There's one more thing."