drop--

The star map on the screen was still flashing. Chen Hao stared at the off-center star marker, his brows furrowed.

“The position is wrong.” He pointed to the projector. “Last night I could say I was seeing things, but now the data has been refreshed three times and it’s still crooked.”

Nana stood in front of the control panel, her finger swiping across the virtual interface. "Coordinate deviation of 0.7 degrees. This is a significant error in the original star map."

"How could something they carved two thousand years ago be accurate to three decimal places?" Chen Hao leaned back in his chair. "But this one place is wrong?"

“We cannot rule out the possibility of human intervention,” she said. “The old world often used steganography to convey information, such as hiding real coordinates in visual illusions.”

"So this isn't a map, it's a puzzle?" He sat up straighter. "And how do we solve it? We can't just have to memorize pi, can we?"

“Try geomagnetic calibration,” he suddenly said. “Remember that abandoned file from the research station? It mentioned a ‘baseline network,’ using abandoned fuel stations for geographic anchoring. Didn’t we have a magnetized steel plate underneath that tin shack we dug up before?”

“The data has been retrieved.” Nana quickly flipped through the data. “This site once provided energy dispatch support for the Old World District Heating System, and its geomagnetic characteristics are highly consistent with the current location of the base.”

"That's right." Chen Hao slammed his hand on the table. "Use it as the origin and re-attach the star chart."

The system began its calculations, and the progress bar slowly climbed. A few seconds later, three points of light lit up simultaneously.

“Match successful,” she said. “Three energy nodes: one is located in the southeast rift valley with active underground heat flow; the second is on the western highlands with more than 4,000 hours of sunshine per year; and the third… is the site of the abandoned fuel station right beneath our feet.”

"So they planned this all along?" he grinned. "Sun, geothermal energy, fuel—it's all in one. We've moved into a place with excellent feng shui."

“It’s not about feng shui,” she said. “It’s about the logic behind the site selection for the project.”

"They're all the same." He waved his hand. "The key is—can it even work?"

“The existing heating system relies on fuel boilers, which are inefficient and consume a lot of materials. Solar collectors are only used for domestic hot water, and geothermal pipes cannot provide stable pressure due to years of disrepair.” She pulled up a pipeline diagram, “The three operate independently without any coordination mechanism.”

“Then let’s connect them together.” Chen Hao stood up and limped toward the equipment cabinet. “Let’s make a master switch, so whoever gets hot can use it, and if it’s not hot enough, we can burn coal.”

"The technical challenge lies in protocol incompatibility." She followed up, "The control systems use different languages, resulting in high signal delays and a high risk of conflict."

“Don’t you have a knowledge base?” He pulled out a pile of old instruments. “You’re in charge of writing the program, and I’ll modify the hardware. Anyway, I’ve disassembled valves eight hundred times.”

He squatted on the ground, unscrewing a rusted connector, humming an off-key song. Nana handed him a wrench; his hand trembled as he took it, and a sharp pain shot through his ankle.

"My injury hasn't healed yet," she said.

"Pain means you're still alive," he grinned. "Dead people don't feel pain."

The two worked all morning. Nana simulated the entire pipeline connection process in a virtual environment, identifying seven bottleneck nodes. Chen Hao, on the other hand, used discarded pressure gauges and wires to assemble a simple monitoring device, which he installed next to a key valve in the underground utility tunnel.

"During the day, when the sun is strong, we prioritize using the solar-heated circulating water tank," he said while connecting the wires. "Once it gets dark, we switch to the geothermal main line. The fuel furnace is only ignited during blizzards or when the temperature drops to minus forty degrees Celsius or above."

“The dynamic scheduling model has been completed,” she said. “By inputting weather data, light intensity, and geothermal flow rate, the system automatically allocates the load to each module.”

"Sounds like a smart farmers market." He plugged in the cable, "I'll just use whichever is the cheapest."

“The analogy is inaccurate,” she said.

"But as long as you can understand it, that's fine."

The test began at 3 PM.

Nana initiated the program, issuing the first command. The solar array slowly turned south, adjusting the angle of the collector plates to maximize reception efficiency. Hot water began to flow into the main circulation pipe.

Five minutes later, the geothermal pump started. A dull tremor came from inside the pipes, and the pressure gauge needle jumped slightly.

"The initial pressure is normal," she said. "We are connecting to the central pipeline network."

Chen Hao stared at the monitor screen, where the three energy streams were displayed in red, yellow, and blue respectively. Red represented fuel, yellow was solar energy, and blue was geothermal energy.

"Here it comes," he said softly.

The three lines gradually approach each other and merge at the central intersection. The temperature curve rises steadily, with the average indoor temperature increasing from twelve degrees to eighteen degrees.

"It's stable." He breathed a sigh of relief. "It didn't explode."

Just then, the alarm went off.

“The temperature in the B-zone circuit dropped sharply,” she said. “There are signs of backflow in the C-branch.”

"Which valve?" He grabbed his toolbox.

"The regulating valve group on the east side of the third underground level."

He limped out the door, the corridor lights flickering with his footsteps. The iron gate to the utility tunnel entrance was half-blocked; he kicked it open and crawled inside.

The area was filled with pipes and steam. He followed the markings to the target valve, only to find the control lever stuck and the pointer swinging violently.

"Remotely lock the abnormal branch," he shouted into the communicator. "Disconnect zone B first, then cut off the geothermal direct supply!"

“Executed.” Nana’s voice was calm. “Room temperature maintained.”

He gritted his teeth and turned the wrench, his joints aching. On the second pull, his foot slipped, and his knee slammed into the metal frame, letting out a muffled groan.

"Do you need any assistance?" she asked.

"No need," he panted. "One more time...and you're done!"

The valve clicked back into place.

“Reopen the access road to Zone B,” he said. “Increase the pressure gradually.”

"Command sent. Pressure recovers, flow returns to normal."

On the screen, the three-color energy streams converged again, forming a smooth heat output curve. The alarm was deactivated.

"It's done." He sat down against the wall, sweat beading on his forehead. "It's so warm."

"The system has achieved autonomous control," she said. "The current mode is 'solar energy as the main source + geothermal energy supplementation + fuel backup,' which reduces overall energy consumption by 62 percent."

"The coal we saved should be enough for a meat meal, right?" He looked up and smiled.

"The cafeteria does not have a redemption system."

"I just said it offhand."

He slowly stood up, leaning against the wall as he walked back to the control room. Nana was recording parameters, her finger lightly tapping in the air.

"Can it be this consistent every day from now on?" he asked.

"Assuming the weather is normal and the equipment isn't broken," she said. "And also, please don't slip and fall again."

“That’s impossible.” He grinned. “I have a natural tendency to trip over things when I walk.”

He sat down in the chair and looked at the graph on the screen. Three streams of energy flowed continuously, like three quiet rivers.

Outside, the sky was darkening, and the wind howled low across the rooftops. But inside, it was warm, and even the windows were fogged up.

"Do you think people two thousand years ago also sat in these kinds of rooms, watching similar screens?" he suddenly said.

“The possibility exists,” she said.

“They knew we were coming.”

"They assumed someone would come."

"Anyway, it's pretty much the same thing." He yawned. "I just want to take a nap now."

"You can go to the rest area."

"No," he shook his head. "I want to look at these drawings again."

Nana pulled up the complete star chart sequence and played it one by one. The last image focused on that shifted star.

Chen Hao narrowed his eyes.

“Wait,” he said. “This star… wasn’t here just now.”