Chen Hao was still squatting, the molten plastic block in his hand softened by the sun. He kneaded it a few times, then suddenly stood up and threw it on the ground.

"The foundation is stable."

He dusted off his pants and walked to the base of the newly repaired wall. The wall wasn't finished yet; the bricks were only a little over two meters high, leaving the top bare and exposed to the wind.

"But this wall is too low."

Susan was coming out of the tool shed, carrying a stack of notebooks. Hearing this, she paused. "Again?"

“It’s not that I’m being nosy.” Chen Hao looked up at the wall. “Last night I dreamed that a three-meter-tall wild boar rushed in and ripped the top off the wall with its horns. I woke up covered in sweat.”

Carl walked over carrying a steel pipe, chuckled upon hearing this, and said, "You can have anything in your dreams."

“Dreams aside.” Chen Hao kicked the foundation of the wall. “We’re safe here now, but we can’t just think about the present. If a large animal really crashes into the wall, is two meters high enough? If it can’t jump over it, can it climb over it? If it can’t climb over it, can it break down? We have to consider all of these things.”

Susan opened her notebook. "With the available materials, we can build the wall to 2.2 meters high, with an error margin of no more than 5 centimeters. Any higher, and we won't have enough steel bars and concrete. You want three meters? Okay, then you can tear down the kitchen and use the lab as a building materials warehouse."

“I didn’t say I wanted three meters,” Chen Hao shook his head. “But two and a half meters is really not enough. Look at this wall, it’s straight up and down. If someone who can climb comes along one day, they can climb it in no time.”

"Something that can climb?" Karl laughed. "You mean a monkey? There aren't even any trees around here, where are we going to find a monkey?"

“I’m not talking about monkeys,” Chen Hao pointed north. “I’m saying, what if there’s something that can climb even faster than a person? Something we don’t know about.”

Susan closed her notebook. "The problem is that you're talking about 'what if,' while we're using 'certain' resources. For every centimeter of height added, the entire wall will require over 300 meters more of brick and stone. Cement won't last. The same goes for steel reinforcement."

“Then we’ll build fewer other things,” Chen Hao said. “The watchtowers can be built later, and the lighting lines can be put on hold for a while.”

"What if something comes at night?" Susan countered. "No lights, no sentries, you just shout?"

"Prioritize defense," Chen Hao insisted. "If the wall breaks, no matter how bright the lights are, it won't help."

Carl looked at this one, then at that one, and finally at Nana. "Don't you robots all talk about logic? Can you calculate this?"

Nana stood still, the optical lens slightly rotating. A few seconds later, her voice rang out: "Okay."

The ground projection lit up, and a 3D model slowly unfolded. The wall structure, tilt angle, and stress distribution were all marked.

"According to database analysis, the maximum jumping ability of large creatures that may appear locally is 1.8 meters, and the climbing limit on smooth walls is about 2.5 meters. If the wall height reaches 2.4 meters and adopts a 15-degree inward slope design, with anti-slip ridges added to the top, it can effectively prevent more than 90% of climbing attempts."

She paused, then added, "This plan consumes 12 percent more materials than originally planned. Current inventory can support it, but the construction of subsequent modules will need to be delayed by three days."

Susan stared at the data for a long time. "Twelve percent...we can accept that."

“I knew it,” Chen Hao grinned. “It’s not that we can’t do it, it’s that nobody has figured out how to do it.”

“But this is not a final guarantee,” Nana continued. “In the event of an extreme impact, such as a mass collision or a direct impact from a heavy organism, there is still a risk of localized collapse.”

"That's better than now." Chen Hao picked up a metal rod and gestured on the wall. "Two and a half meters long, with a bevel, and a ridge on top. We'll start modifying it tomorrow."

Carl frowned. "The blueprints need to be redrawn, and the construction team needs to be retrained."

“There are only four of us on the construction team,” Chen Hao laughed. “Five minutes of training will suffice—just add thirty centimeters up, and then close the opening inwards.”

Susan didn't speak, but looked down at her notebook and calculated for a while before nodding. "Okay. I can adjust the reinforcement density to save some steel."

"Then it's settled?" Chen Hao looked at Nana.

"The plan has been entered into the system," Nana said. "The new parameters have been synchronized to the terminal, and we can start work at any time."

Carl rolled up the old blueprints and stuffed them into a waterproof tube. "Six o'clock tomorrow morning?"

"Six o'clock," Chen Hao replied without turning around.

The sun was setting, casting long shadows on the unfinished wall. Chen Hao used a metal rod to draw a line on the brick surface.

"Right here."

Susan put away her notebook and turned to walk towards the tool shed. She paused as she passed Nana. "Can you save that model you were working on?"

“Automatic backup has been completed,” Nana said. “Number F565-h01, named ‘Compromise Envelope Optimization Scheme’.”

"Easy to remember." Susan gave a wry smile and walked away.

Carl placed the steel pipe against the wall, wiped the sweat from his face, and said, "Do you think our wall will be called 'Chen Hao's Wall' from now on?"

"Stop dreaming," Chen Hao laughed. "At most, it'll be called 'the wall that almost collapsed'."

"That's better than nothing." Carl stretched. "At least I don't have to worry about the ground exploding every day."

“The underground is stable.” Chen Hao looked up at the sky, “but who knows what’s waiting between the sky and the ground.”

Nana stood still, her eyelight flickering, entering nighttime standby monitoring mode. Her camera was focused on the newly defined construction boundary, continuously receiving environmental signals.

The wind blew in from the north, carrying a faint smell of burning—the remnants of yesterday's furnace. At the base of the wall, the discarded molten metal block had been trampled into the soil, only a corner protruding.

Chen Hao was still standing there, his hand resting on the brick wall. He touched the top edge and felt it was a bit rough.

"We need to make the anti-slip edges more solid tomorrow," he said.

“The materials list has been updated,” Nana responded. “The required length of angle iron is thirty-seven meters, and the cutting specifications are uniformly ten by ten millimeters.”

"That's enough." Chen Hao nodded. "Prepare all the ingredients tonight."

Carl patted him on the shoulder. "I'll go check the power supply box and see if we can run a separate cable for the cutting machine."

"Go ahead." Chen Hao let go of her hand. "Don't let it trip the circuit breaker again while you're working on it."

Susan emerged from the tool shed, a roll of measuring rope in her hand. She walked to the eastern section of the wall and began to draw the line for positioning.

“It’s 2.4 meters high here, and extends 20 meters to the west,” she said.

"Let me help you." Chen Hao walked over and took the rope.

The two stretched the line straight and secured it to the wooden stakes at both ends. Susan leaned over and looked at the level. "It's two millimeters off."

"It's nothing." Chen Hao pressed down on the stake with his hand. "You can't see it with the naked eye."

“But the data shows that,” Susan readjusted.

Nana was recording the coordinates, saying, "The new baseline has been marked, and the error is within the allowable range."

"You guys are really something," Chen Hao shook his head, "not willing to give an inch."

"It won't collapse if we don't let it." Susan put away her instruments. "If this wall is crooked, every brick will follow suit."

"I'll listen to you." Chen Hao raised his hand. "I won't say anything more."

As dusk fell, the last rays of sunlight touched the top of the wall. Chen Hao stood on the newly marked elevation line, looking up at the blank space.

"By this time tomorrow, the first layer should already be built here."

"The prerequisite is that we start work promptly at six o'clock in the morning," Susan reminded.

"I'll set three alarms," ​​Chen Hao laughed.

Carl walked back from the power supply box. "The power is fine, it's just that the wiring is old and can't withstand high loads for long periods of time."

"Just enough for a short time," Chen Hao said. "I'll rest after I finish cutting the angle iron."

“We still have to weld,” Carl said. “Nobody can guarantee the joints will be secure.”

"I'll take care of the welding torch." Chen Hao patted his chest. "The skills I honed last time by burning plastic will have to come in handy."

“Be careful not to set yourself on fire,” Carl said.

"I can just wear another layer of clothing." Chen Hao looked down at himself. "I'm not afraid of the heat anyway."

Susan rolled up the measuring rope and put it in the toolbox. "The materials are all checked and should be here by tomorrow morning."

"That's all then." Chen Hao flexed his wrists. "I'll go back to sleep when it's completely dark."

"Didn't you just say you set three alarms?" Carl asked.

“Yeah,” Chen Hao laughed. “One isn’t enough, two might be too much to forget, and three would be needed to drag me out of bed.”

"You really expect to wake up on time?" Susan glanced at him.

"No," Chen Hao said honestly. "That's why I told Nana to spray water directly on my face."

Nana's eye light flashed. "Reminder task set. Time: 5:30 AM tomorrow. Execution method: Facial spray activated."

"Look!" Chen Hao pointed at Nana, "You keep your word."

Susan closed the toolbox lid. "I hope you don't oversleep and spray three times."

“Once is enough,” Chen Hao said. “No one can bear the pain of water getting into their ears.”

Carl smiled and shook his head. "Then you should get some sleep."

Chen Hao took one last look at the empty line on the top of the wall, then turned to leave. After taking two steps, he stopped again.

"Oh, right," he said, "whoever arrives first tomorrow, remember to set up the template first."

“I’ll do it,” Carl said.

"Don't prop it up crookedly," Chen Hao said.

“You’re the one most likely to make a mistake,” Carl retorted.

Chen Hao smiled and didn't refute. He stepped on a loose paving stone, making a soft click.

He glanced down at it.

The bricks weren't cracked, but the soil underneath seemed a bit loose.