Chen Hao's hand was still suspended in mid-air, his fingertips only a centimeter away from the black cannon. He opened his mouth, about to utter his new idea, when Nana suddenly raised her hand, her mechanical arm slicing across and blocking his movement.

"Wait a moment."

Her camera panned to the monitor screen on the wall. A red light flashed, and the alarm, though lowered in frequency, continued to sound. A line of text appeared on the screen: Heating system at 97% load; fuel reserves estimated to last 14 days.

Chen Hao froze, his excitement vanishing as if doused with cold water. He withdrew his hand, scratching the back of his head. "Is this number wrong? Didn't we just haul three barrels of fuel oil back from the ruins in the East District a few days ago?"

Nana didn't turn around. She slid her finger across the control panel, bringing up the energy consumption curve. "Over the past 72 hours, daily energy consumption has increased by 18%. The outside temperature is 12 degrees lower than predicted. Although the insulation layer has been repaired, the rate of heat loss is exceeding expectations."

She paused, then added, "The current fuel supply won't last until the spring signal appears."

Chen Hao stared at the ever-rising red line, his lips moving slightly. He slumped back in his chair with a thud. "So we're going to start messing around with new energy sources again? I was just getting into the swing of things."

“Your emotional fluctuation level is currently too high,” Nana said. “Your heart rate is faster and your speech is quicker; these are typical signs of escaping reality.”

“I’m not running away!” He sat up straight. “I just think… could you let me win a game first before we talk business? I’ve lost five games in a row.”

"Winning or losing does not affect the rate of energy consumption."

Chen Hao sighed, ran his hand through his hair, then put it down again. He looked at the screen; the red warning line felt like a needle pricking his eyelids. He rubbed his face, his voice lowering, "Fine. What do you suggest we do?"

Nana brought up the database interface and entered the keyword: sustainable heating solutions for extreme environments. A few seconds later, two options appeared on the main screen—passive solar thermal collection and shallow geothermal energy utilization.

"Technical approach one: solar thermal collection. The principle is to collect sunlight through heat-absorbing materials and convert it into heat energy to be introduced into the heating cycle. The advantages are that the materials are readily available, the construction period is short, and it is suitable for rapid verification."

She switched the camera to "Technical approach two: geothermal energy. This involves heat exchange using underground constant-temperature layers. The advantage is stable output, unaffected by weather. The disadvantage is that it requires drilling equipment, which is currently unavailable at the base."

Chen Hao's eyes lit up after hearing this. "Then why choose? Geothermal sounds exciting! Digging a hole, drilling a well, booming, and hot air rising up—how ​​awesome is that?"

“The last search for drilling equipment was unsuccessful,” Nana said calmly. “The nearest engineering warehouse has been buried by a sandstorm, making excavation too risky. Moreover, a failed drilling operation would waste a lot of manpower and time.”

"Human resources?" Chen Hao pointed to himself. "I'm human resources now. Aren't you quite capable too?"

“My design does not include high-intensity geological operations,” she said. “Forcing it could overload and damage the joint modules.”

Chen Hao rolled his eyes. "You always say it will break, but when has it ever actually broken? Last time you dismantled the boiler, you burned yourself up, but you were still alive and kicking."

"That was a temporary malfunction of the cooling system, not a normal operating condition."

"Come on," he waved his hand. "Anyway, I think geothermal is more reliable. Solar energy is all about the weather. What if it's cloudy for a whole series? We'd freeze to death!"

“The current sunshine cycle is stable.” Nana pulled up the weather records. “The probability of sunny days in the next fifteen days is 83%. However, geothermal projects require at least twenty-two days from preparation to testing, which is far beyond the remaining lifespan of the fuel.”

Chen Hao fell silent. He stared at the solar energy item for a long time, then suddenly grinned: "Do you remember when we were playing chess earlier? I said I was going to set up a strategy, but you insisted that I was making a slow move."

"Your pawn advancing seven steps forward does indeed lack offensive threat."

“But I’m paving the way for later.” He pointed to the screen. “Isn’t developing solar energy now like infantry? It looks slow, but it’s actually laying the groundwork. Once it’s up and running, we can then move on to geothermal energy. A two-pronged approach is much more stable, isn’t it?”

Nana paused for two seconds, the camera flickering slightly. "Your analogy holds true. The current situation has entered a mid-game attrition phase, and we must adjust our resource allocation strategy. Prioritizing solar energy projects as a short-term supplement is reasonable."

"I knew you could understand human speech." Chen Hao slammed his hand on the table and stood up, his chair creaking as it slid backward. "Then what are we waiting for? Let's get started!"

He walked a few steps to the old toolbox in the corner, squatted down, and opened it with a clatter. Inside were wrenches, screwdrivers, several rolls of rusty copper wire, and a half-empty bottle of sealant. He rummaged through it, pulled out a pair of calipers, and then found a worn-out voltmeter.

“These should be enough to make a sketch,” he said. “I remember there used to be those black panels on the roof of the school; a day's heat could last for two days. Could we make a mini version?”

Nana has begun compiling a list of available materials. "Discarded circuit boards can be used as support substrates, carbon-coated glass left over from the laboratory has a certain heat absorption capacity, and with the addition of copper pipes from the recycled piping system, a basic heat conduction structure can be constructed."

"Sounds like building Lego." Chen Hao grinned. "Then you design it, and I'll build it. But seriously, does this thing actually work?"

"Preliminary simulations show that if a 10-square-meter heat collector surface is built, it can provide the equivalent of two barrels of fuel oil per day," she said. "It cannot completely replace fuel, but it can extend the fuel lifespan to more than three weeks."

Chen Hao whistled. "Three weeks? That's plenty of time for us to figure out a solution."

He picked up all the tools, walked back to the control panel, and put them on the table. The clanging of metal echoed in the room. He pulled out a chair, sat down, and casually drew a square on a piece of paper.

“Then it’s settled. Solar power will go first, geothermal will come later.” He looked up at Nana. “But you have to promise me one thing.”

Please explain.

"Once this is settled, you have to let me win a game of chess."

"The outcome depends on the efficiency of both sides' strategy execution; there is no room for human manipulation."

Just tell me if you can or can't!

Nana paused for a second. "If you can provide three effective optimization suggestions during the design process, I can adjust the decision weights and allow one suboptimal move."

"Deal!" Chen Hao laughed. "You said it yourself, don't go back on your word later."

He lowered his head and began to draw, the pen scratching across the paper. Nana simultaneously projected a three-dimensional structural model, calculating thermal efficiency and marking key nodes.

The room fell silent, save for the clatter of keyboard clicks and pen scratching on paper. Outside, the wind and snow continued to howl, but the atmosphere inside had changed.

When Chen Hao was drawing the third conduit, he suddenly stopped.

"Wait a minute." He looked up. "You said we'd use carbon-coated glass for the heat absorbers, but there are only four of those, which add up to less than six square meters. Where are we going to find the missing four meters?"

Nana pulled up the inventory list. "There's a batch of spare optical lenses in the lockers on the west side of the research station, originally used for focusing experiments. They have a reflectivity of up to 92% and can be used to increase light density, indirectly increasing the effective heat collection area."

"You can do this with lenses?" Chen Hao's eyes lit up. "Then hurry up and bring them out, let's try arranging them."

“It requires two people to move it,” she said. “The lenses are fragile, and it is too risky for one person to handle them alone.”

“Okay, I’ll go get it. You keep calculating here.” He stood up and threw the pen on the table. “But I’m warning you, if we work well together, you’d better throw the game more obviously next time.”

“I won’t hold back,” Nana said, “but I can make you notice my weaknesses.”

"Fine," Chen Hao grinned. "It's better than being utterly annihilated by you."

He walked towards the door, but stopped halfway through his step.

"By the way, is that broken chessboard still in the living quarters? I want to study your strategies again when I get back later."

“The chessboard has been put away in its storage box and placed in the left compartment under the sofa,” Nana said. “I suggest you focus your attention on the task at hand.”

"Okay." He waved his hand. "Once I bring the lenses back, we'll get back to work."

The door opened and closed. Nana continued adjusting the parameters on the screen, the energy consumption simulation data scrolling and refreshing.

A few minutes later, footsteps were heard outside the door, followed by the dull thud of metal clashing.

The door was pushed open a crack, and Chen Hao's voice squeezed in from outside: "Hey! This box is stuck! Come and lend a hand!"