It was six o'clock in the morning, just as dawn was breaking.

Chen Hao bent down to tighten his shoelaces. This time, he was wearing non-slip boots he had found in the warehouse, with rough treads on the soles. He stood up, dusted off his trousers, and dragged the sled leaning against the wall half a meter toward the door.

Nana was already standing outside the door waiting for him.

She didn't speak, but turned her head to look at the snow, then looked up at the sky. The sun had just peeked through the gaps in the clouds, its light not dazzling on the snow, but enough to make out the gentle slope ahead.

"Let's go." Chen Hao exhaled a puff of white breath. "While the snow is still hard."

The two pushed the sled to the open space, one after the other. Chen Hao walked around it halfway, squatted down and touched the bottom of the track, running his fingers along the seam; it felt fairly smooth.

“You sit in the back,” he said. “I’ll pull you.”

Nana didn't move, she just said, "According to the original plan, you should control the center of gravity from the back, and I will guide you from the front."

"Who called for a stop when the car overturned?" Chen Hao stood up. "You reacted quickly. If it tilted, you could just hold onto the handrail. If I fell out, I could at least roll twice before getting up."

Nana blinked, and the system began calculating the power distribution model. Three seconds later, she said, "Accept the adjustment plan."

She boarded the sled first, sitting at the back of the platform with her legs together and her hands gripping the edge metal bars. Chen Hao took a deep breath, bent down to hold the handrails, pushed his shoulders forward, and pushed off with his feet.

The sled wobbled and then began to move.

At first, it was very slow, like dragging a stubborn iron plate. Chen Hao snorted and put in more effort. His shoes slipped on the snow once, but he quickly found his rhythm, leaned forward, and used his weight to pull himself forward.

Suddenly, the track cut into the snow with a "whoosh".

The speed suddenly increased.

The wind immediately rushed into his ears, making him shiver. The scenery before him began to rush past, and the snow beneath his feet became smooth and flat, as if covered with a layer of glass. He couldn't help but laugh out loud, his voice broken and intermittent by the wind.

"It flew! It really fucking flew!"

Nana didn't speak, but leaned back slightly to maintain her balance. Her hair was blown back and clung to the collar of her protective suit. The scanning system automatically recorded the current speed, tilt angle, and ground friction coefficient.

The gentle slope is just 30 meters away.

They rushed down.

The further down he went, the faster he went. Chen Hao felt his feet were floating, as if he were being pushed along without any effort. He grinned, tears welling in his eyes from the wind.

"This is much faster than walking! We'll use this to transport things every day from now on!"

No sooner had he finished speaking than a section of the sled's right front collapsed.

It wasn't a big ditch, just a palm's depth, but it somehow got stuck on the right-side rail. The entire car body instantly veered to the left, then twisted violently, and was thrown sideways as if it had been kicked.

Chen Hao had no time to react.

He swayed, his hand slipped from the handrail, and he was thrown sideways into the snowdrift. He landed on his back, making a dent, and his head hit the ground with a buzzing sound.

Nana reacted quickly, grabbing the edge of the platform before it overturned. Although she was also knocked down, she used her mechanical arm to brace herself against the ground, preventing the sled from completely tipping over. It finally slid diagonally for more than ten meters before crashing into a frozen tree stump and coming to a stop.

The wind calmed down.

The surroundings suddenly became quiet.

Chen Hao lay panting in the snow, his chest heaving, his face covered in snowflakes. He blinked, spat out a small pinch of snow from his mouth, and slowly sat up.

"I'm alive?"

Nana had regained her footing and was walking back. She reached out and helped him up.

“Vital signs are normal,” she said. “Minor impact, no fractures.”

Where's my hat?

Nana pointed. Five meters away, a gray woolen hat hung on the withered grass, like an abandoned bird's nest.

Chen Hao staggered over, picked it up, brushed off the snow, and put it back on his head. His left sleeve was torn, and his arm was scraped raw, with blood seeping out.

"Does it hurt?" Nana asked.

"It's alright." He shrank his arms. "It's not like it's the first time I've fallen."

They walked back to the sled together. It was tilted to one side, and the right track was noticeably bent, as if someone had stepped on it. A strap had come loose and was hanging down to the ground. There was a small crack at the joint of the fenders; it wobbled when touched.

"Top speed 38 km/h." Nana pulled up the data, "Tilt 17 degrees and became unstable at 3 o'clock."

"So, you mean it'll flip over if it's even slightly tilted?"

"yes."

Chen Hao walked around the sled once, then squatted down and touched the bent part with his hand. The metal was slightly deformed, but not broken.

Can it be repaired?

“It can be reinforced,” Nana said, “but a lateral support structure is needed to prevent lateral stress concentration.”

"Then add it."

“Materials are limited. I suggest disassembling the spare titanium alloy plates from the exoskeleton and welding them to both sides of the bottom.”

"You weld, I'll just hold you up."

"We also need stabilizer bar connectors. We only have six rivets left in stock."

“That’s enough.” Chen Hao stood up. “Tighten this loose strap first.”

He bent down to tie it, but his fingers were so cold they wouldn't obey him, and the two knots he tied came undone. In the end, Nana took the ribbon and quickly secured it.

"Don't make me sit in the front next time," Chen Hao said, rubbing his hands together. "It's too easy for me to fly off."

"Then you'll adjust your position?"

“Okay.” He nodded. “I’ll sit in the back and pull, and you sit in the front and steer. You react faster than me, so you can stabilize the situation before we encounter any pits. And you’re strong, so you can withstand a rollover.”

Nana thought for two seconds: "The power distribution is more reasonable. I accept the suggestion."

"Then it's settled."

Nana walked to her toolbox and took out a portable welding torch and a cutting knife. She disassembled the exoskeleton components, picked out two intact titanium alloy strips, and placed them under the slide rail.

"It will take five minutes to complete the welding."

"You do your thing, I'll go stretch my legs over there." Chen Hao walked to a rock not far away, sat down, and shook his arm. The wound was still bleeding, but he ignored it.

A few minutes later, sparks flashed a few times.

Nana completed the reinforcement. The newly installed crossbars were attached to the outside of the slide rails, like adding two short legs to the sled. She gently shook it to test it, and the sled was much more stable.

“The structural strength has been increased by 22 percent,” she said, “but high-speed travel over complex terrain is still not recommended.”

"Understood." Chen Hao walked back. "Try low speed first, then gradually increase the speed."

They rearranged the seats. Nana sat at the front, gripping the front of the armrests tightly. Chen Hao stood at the back, his hands on the platform, ready to exert force.

“Slow down this time,” he said. “We’re not in a rush.”

He pushed off with his feet, and the sled slowly started moving.

The speed was much lower than before, and the gliding was smooth. The two walked back along the same route for a while, confirming that there were no unusual noises or shaking.

“It can speed things up,” Nana said.

Chen Hao nodded and gradually increased his strength. The sled started moving again, but this time he controlled the pace and slowed down in advance when encountering bumps or undulations.

When they reached the top of the slope, they stopped to take a look.

"Should we try again?" Chen Hao asked.

“Okay,” Nana replied, “but you need to maintain a straight trajectory and avoid turning.”

"Then go straight down."

He took a deep breath, steadied himself, and leaned his shoulders forward.

The sled began to descend.

They gradually increased their speed, and the wind blew against their faces again. This time, they didn't laugh or shout; they simply focused intently on the snow ahead.

Ten meters, twenty meters, thirty meters...

Just as they were about to reach the bottom, a shallow ditch suddenly appeared in the snow ahead.

Nana immediately reached out and grabbed the edge of the platform, leaning forward to press down. Chen Hao also reacted, jerking in the opposite direction to try and counteract the tilt.

The train swayed slightly, its right rail grazing the edge of the ditch before finally coming to a stop.

They successfully navigated the obstacle course, gliding for a while before coming to a natural stop.

"It's a success," Chen Hao said, panting.

“There was no overturning.” Nana turned to check the slide rail. “There is slight wear on the right side, but no structural damage.”

"It seems changing the location worked."

"The personnel layout optimization is effective."

Chen Hao grinned and wiped his face. Only then did he realize that the wound on his left hand had reopened, and blood was dripping from his fingertips onto the sled platform, leaving several red spots.

Nana saw it.

She reached into her toolbox, took out a dressing, tore open the packaging, and handed it to her.

"You can stick it on yourself."

"You know I'm not very good at this?"

"You pasted it upside down last time."

"That was an accident."

He took the dressing and clumsily pressed it onto the wound. Nana watched without saying a word.

After attaching it, he patted the sled.

"This thing still has potential."

"The premise is to prevent it from flipping over again."

"Of course." Chen Hao looked up at the sky. "The sun is out, and the snow is starting to soften."

"It is recommended to end the test and return to base to plan the next steps."

“No rush.” He shook his head. “Let’s try one more time. I want to see just how fast it can run.”

Nana glanced at him.

"The risk factor has increased."

"I know," Chen Hao smiled. "But if we don't even dare to try, we'll only ever be able to crawl slowly."

He stood back again, holding onto the platform with both hands.

Are you ready?

Nana settled down and gripped the armrests tightly.

"Ready."

Chen Hao took a deep breath and pushed off with his feet.

The sled shot off.