Life on the island gradually transformed from initial wretchedness and panic into a steady, peaceful rhythm. Springs passed into autumns, cold into heat; Lin Wanying and Chen Hui spent countless days and nights here. They had long adapted to the climate and rhythm of the island, built a sturdy shelter, familiarized themselves with which plants were edible, where fresh water could be found, and gradually mastered the laws of survival on the island.
Besides survival, their daily lives mostly consisted of exploring and researching this mysterious island. Starting from the edge, they ventured deeper into the interior day by day, accumulating clues bit by bit.
One early spring day, when the sunlight finally pierced the dense canopy of the forest, illuminating the moss on the ground, Chen Hui and Lin Wanying discovered an ancient stone door half-hidden among vines and moss deep in the forest.
After clearing the debris, they found that this stone door had no obvious handle or mechanism, but rather a combination of numbers and symbols carved on its side.
Chen Hui looked quietly at this door covered in dust and time, saying softly: "The symbols on this stone door bear a striking resemblance to the mathematical derivation formulas in the *Nine Chapters on the Mathematical Art*!"
Lin Wanying squatted down, carefully examining the stone carvings on the door, her tone full of concentration: "These carvings on the side... are actually problems for the three-variable equation solving method from the *Origins of Equations*."
The two exchanged a smile, seemingly communicating some tacit understanding and determination. The bond forged through shared hardships during this time had already made their cooperation require no verbal reminders.
Chen Hui reached out to touch the stone carving, finding its surface smooth, clearly a result of precise sculpting: "This is not an ordinary calculation method, this is a mathematical puzzle... This door will only open if the correct numerical value is derived."
Lin Wanying took out the calculation chips she always carried with her, rapidly laying out calculations on the ground, murmuring softly: "The 'Tian Yuan' method, surplus and deficit calculation, restoring the original value..."
After some deduction, she exchanged a glance with Chen Hui, and the two simultaneously reached out to press the carved marks on the stone door.
"Let's try this value."
Boom—!
The sound of mechanisms operating within the stone door rang out. As dust settled, the ancient stone door slowly opened, releasing a heavy and profound aura from within.
Inside was a staircase leading into the unknown.
"What exactly is hidden down there?"
Chen Hui looked into the pitch-black depths, his eyes complex.
Lin Wanying took a deep breath and stepped inside—
"Whatever it is, we must go in and investigate."
After exploring for a while, they discovered a massive underground palace. The interior was not an ordinary cave, but featured meticulously designed passageways. The walls were covered with ancient symbols and mathematical formulas; every mechanism seemed to have been rigorously calculated and designed.
"These mathematical problems... are extremely similar to the methods in the *Nine Chapters on the Mathematical Art*."
Lin Wanying reached out to touch the symbols on the wall, her gaze gradually becoming focused.
"These do not seem like defensive mechanisms, but rather a trial."
They arrived at the core of the first floor. Carved on the giant stone door before them was a mathematical puzzle—
"'Tian Yuan' enters the square, surplus and deficit cancel out; if four times less eight equals half the value, what is the original number?"
"This is a variant of the 'Tian Yuan' method."
Chen Hui and Lin Wanying quickly began calculating. The calculation chips flew across the floor, written calculations and mental deductions intertwining, ultimately arriving at the answer.
When they matched the numbers to the mechanism on the stone door, a rumbling sound echoed, and the stone door opened. The trial of the first floor was over.
"The trials and designs here... are actually a combination of mathematics and mechanistics?"
Chen Hui marveled slightly. This was completely different from any known mechanistics in the world.
"Why do I feel like this underground palace is not a treasure vault or a base, but more like a test of wisdom left for future generations?"
As they entered the second floor, they were greeted by even more complex mechanisms and mathematical puzzles.
The calculations here involved advanced mathematical derivations such as "dividing circles to find the area" and "surplus and deficit method." The mechanisms on the walls were also more precise; some even required physical mechanics and lever principles to unlock.
In this underground palace filled with wisdom and ancient mathematics, they began an unprecedented journey of exploration.
"Who exactly has been to this island?"
"Who are the masters... that designed these trials?"
They could not predict the answers, but they knew this underground palace would become the direction of their future exploration.
Time passed. Several months had gone by since they unlocked the stone door. Every time a mechanism was solved, new mechanisms and mathematical puzzles awaited them at the next corner. As the days went by, their pace of exploration became steadier, transitioning from their initial tension and caution to confidence and anticipation for the next challenge.
During this time, Lin Wanying and Chen Hui not only deeply studied the mechanisms and mathematical puzzles of the underground palace, but also gradually adapted to island life.
The trials on the second floor of the underground palace were far more complex than the first. In addition to employing profound mathematical deductions such as "surplus and deficit method" and "circle and square integration method," they also involved precise mechanical technology like lever mechanics and gear operations.
After falling into difficult situations several times, they ultimately found the key to cracking them, successfully pushing open the door leading to the third floor.
However, it was at this moment that Lin Wanying's body began to show anomalies.
One day, when they returned to the cave to rest, Lin Wanying suddenly felt a wave of dizziness. She pressed her forehead, frowning slightly.
"Are you alright?" Noticing something wrong with her expression, Chen Hui quickly supported her arm, his tone laced with worry.
"...Just a little dizzy." Lin Wanying shook her head gently, murmuring: "I've felt a bit off these past few days; occasional nausea, and my appetite has changed..."
As soon as she finished speaking, the two exchanged a glance, realizing something almost simultaneously—
"Are you..." Chen Hui's voice trembled slightly, his eyes reflecting uncertainty and surprise, "Are you... pregnant?"
Lin Wanying froze for a moment, a myriad of thoughts flashing through her mind.
She closed her eyes, carefully recalling her physical condition over the recent period, and combined it with calculation chip deductions for the months. Her fingertips trembled slightly. Finally, she nodded gently: "It... should be."
Her voice was very soft, yet it struck like thunder, setting off turbulent waves deep in Chen Hui's heart.
He remained stunned for a long while, as if unable to fully digest this fact. Then, he suddenly chuckled softly, his eyes filled with tenderness: "We... are going to have a child."
Lin Wanying gently brushed her lower abdomen, feeling the life within. A soft smile graced her lips: "Yes, our child."
At this moment, the weight on both their hearts seemed to lighten. The past flames of war and the desperate straits of their escape seemed to be filled by this impending new life.
Having a child meant that every step they took in the future had to be more cautious.
"The trials of the underground palace continue, but now, we are not just exploring for ourselves; we must also consider our child."
Chen Hui looked at Lin Wanying, his tone firm, "We need two paths—one is to continue exploring the underground palace, as there might be more secrets about this island inside, or even clues to leaving."
"The other... is to let the outside world discover our existence."
Lin Wanying nodded. Naturally, she understood his meaning, "We need to leave markers so people at sea can discover this place."
The two began to think about how to make this isolated island "visible."
After many discussions, they designed several methods from various angles, hoping to one day attract the attention of passing ships—
In an open area of the island, Lin Wanying used massive white stones to form a giant "calculation chip pattern." This pattern was based on the sequence arrangement from the *Nine Chapters on the Mathematical Art* and was extremely conspicuous from the sky. If a ship were to look from a high vantage point from afar, they would highly likely notice the anomaly.
Chen Hui, using dead wood and dry grass, prepared several large bonfires. Once a ship approached, they could quickly ignite them, creating smoke signals to alert distant sailors to the island's presence.
They also searched for metal or shells along the cliffs that could reflect sunlight, placing them at the peaks of the mountains. Once the sun shone, they would emit sparkling light, perhaps catching the eyes of sailors.
When everything was prepared, night fell again. The bonfire burned inside the cave, illuminating their calm yet hopeful faces.
"With a child... we must survive." Lin Wanying said softly, her fingers gently stroking her slightly bulging abdomen, her tone firmer than ever before.
"We definitely will." Chen Hui gently held her hand, his gaze resolute, "We won't just survive; we will ensure this child is born into a future worth looking forward to."
"We will leave here and return to the Central Plains."
"We will protect each other, and we will protect this child."
The night wind blew gently, sweeping away all unease, bringing a brand new future.
When time was no longer measured in days but by Lin Wanying's gradually growing abdomen, the two seemed to feel the passage of time much more realistically. Chen Hui began learning to craft more tools and furniture, building a safe and warm resting place for Lin Wanying. Lin Wanying carefully calculated celestial phenomena and seasonal changes to ensure she welcomed the child's birth at the safest possible time. Over this half-year, they not only further explored the island's environment but finally unlocked the third floor's trial in the underground palace.
The puzzles and mechanisms on this floor were even more complex, involving advanced mathematical derivations like the "Tian Yuan method," "double difference proportions," and "surplus and deficit method," combined with lever mechanics and gravity devices. The two fell into difficult situations several times, but ultimately, relying on wisdom and patience, they successfully cracked the final mechanism of the third floor.
When the stone door slowly opened, they didn't rush to continue downward. Instead, they exchanged a glance, tacitly making the same decision—
Pause exploration and prepare to welcome the new life.
Although life on the island was tough, this time, they were no longer living just for themselves, but preparing for the unborn child.
Lin Wanying's abdomen was now slightly protruding, her movements becoming somewhat sluggish. This led Chen Hui to shoulder more responsibilities, striving to create an even safer and more comfortable environment for her.
They chose a wind-sheltered cave as a temporary residence, reinforcing the entrance with timber and stones to ensure storms wouldn't affect the interior.
Chen Hui built a simple bamboo bed so Lin Wanying could rest more comfortably, while Lin Wanying began calculating celestial phenomena and climate changes to deduce the best time and location for childbirth.
"Based on the calculations of wind direction and tidal changes over the past few months, the next few months should be the most stable period." As she calculated, she whispered, "If the child is born during this time, it will be safer."
Beside her, Chen Hui was polishing a wooden stick, a simple harpoon he made to catch fish and supplement their food. Hearing her words, he looked up and smiled: "Your child hasn't even been born yet, and is already being arranged by mathematics?"
Lin Wanying chuckled softly, stroking her slightly protruding abdomen: "He is my child; of course, he cannot be without calculation."
Chen Hui put down the tools in his hands, walked over to her side, and gently held her hand, his tone tender: "He is not just your child, but also mine."
She looked at him with an unusually soft gaze: "I know."
At this moment, the loneliness of the island seemed to vanish. Their hearts were tightly linked together. There were no past flames of war or conspiracies, only an impending hope.
While preparing for the child, Chen Hui began to consider an issue—they could not be trapped on this island forever.
One day, as the two sat by the sea gazing at the endless horizon, Chen Hui spoke slowly: "Although this island is stable, it is ultimately not our home."
Lin Wanying fell silent for a moment, then nodded gently: "I also don't wish for our child to be trapped here for a lifetime."
He turned to look at her, his gaze firm: "We must find a way back to the Central Plains, no matter how many years it takes."
Lin Wanying frowned slightly: "But we don't have enough tools right now, not even a complete boat..."
"That's why we must prepare."
Chen Hui's tone was certain: "We can continue to leave markers on the island, trying to attract passing ships. If that path doesn't work, we will build a boat ourselves, find the nearest ocean current direction, and attempt to sail away from here."
Time flew. As night fell again, the waves gently slapped the sandy shore, and the world seemed to fall silent for a moment.
Lin Wanying's contractions arrived on schedule.
Inside the cave, Chen Hui guarded her nervously, fine sweat beads forming on his forehead, but his hand never left hers.
"Take deep breaths... take it slow..."
Lin Wanying gritted her teeth, her forehead covered in sweat, but her eyes remained resolute.
Time passed bit by bit. Finally, with a weak but clear cry of a baby, the island's night was illuminated by new life.
Chen Hui picked up the tiny infant. Looking at his wrinkled little face, an indescribable surge of emotion and excitement swelled in his heart.
"It's a boy."
Lin Wanying smiled weakly, leaning gently in his embrace, her eyes gazing tenderly at the little life.
"We should give him a name."
Chen Hui pondered for a moment, then spoke slowly: "Let's call him Chen Wenbin."
"Wen, for inheriting wisdom; Bin, for combining civil and martial virtues."
"I hope he can be accomplished in both the pen and the sword, not only inheriting our knowledge but also possessing his own strength."
Lin Wanying softly murmured it once: "Chen Wenbin..."
The corners of her mouth curled up as she gently reached out to stroke the child's forehead. This tiny life would be their hope for the future.
"Very well, that will be his name."
Holding the newborn infant and looking at Lin Wanying's exhausted yet gratified smile, Chen Hui said softly: "From now on, we are no longer two isolated individuals, but a family."
Lin Wanying nodded gently, her gaze tender and firm: "That's right. No matter what the future holds, we will face it together."
The night was silent. The bonfire in the cave flickered, casting the shadows of the three leaning on each other.
The fluster of first-time parents.
The birth of Chen Wenbin brought unprecedented vitality to the isolated island, but it also drastically changed the lives of Lin Wanying and Chen Hui.
During their first year as parents, the two had almost no time to study the underground palace, nor did they have the energy to think about leaving.
The infant cried day and night. Preparing food, ensuring warmth, preventing illness—these tasks made Chen Hui, who once devised brilliant strategies on the battlefield and in the imperial court, completely at a loss.
"Why is he crying again?"
"Is he hungry, or cold?"
"How should I know?"
"Then... hold him and coax him a bit?"
For the first time, the two showed complete helplessness in caring for a baby. The two people who could calculate complex tactics and mechanical mathematics couldn't calculate the needs of an infant.
Sometimes, when Chen Hui carried the endlessly crying Chen Wenbin at night, pacing back and forth in the cave with a helpless expression, Lin Wanying couldn't help but chuckle: "The way you hold the child is stiffer than how you hold calculation chips."
Chen Hui sighed: "This child is much harder to understand than mathematics."
"That's because you can't use calculation to explain his behavior."
"But can you?"
"...No."
The two exchanged a smile. Although this parenting journey was filled with chaos and challenges, whenever they saw the sleeping child, all exhaustion became insignificant.
Time flowed like water. In the blink of an eye, a year passed. As Chen Wenbin gradually grew, Lin Wanying and Chen Hui's parenting skills also became more proficient, finally managing to recover a bit of sanity from the flustered days.
When the child started learning to crawl, babble, and even grab food on his own, Lin Wanying and Chen Hui finally breathed a sigh of relief, shifting their minds back to the exploration of the underground palace.
"The trials of the underground palace aren't over yet. We haven't found the true secret of this island."
Carrying a bamboo basket filled with food and water pouches, Chen Hui and Lin Wanying stepped into the entrance of the underground palace once again.
"We have been stalled for a year; it is time to move forward."
However, this time, unlike in the past, a wobbly little figure trailed behind them.
Taking short steps and wide-eyed, Chen Wenbin stared curiously at the calculation chips in their hands and the strange mechanisms inside the underground palace.
"Look, he seems very interested in these numbers and mechanisms."
Lin Wanying raised an eyebrow, looking at Chen Hui with a light laugh: "Your son came into contact with the *Nine Chapters on the Mathematical Art* much faster than you did."
Chen Hui helplessly rubbed his temples: "Does this count as talent?"
"Of course this is talent." Lin Wanying bent down, watching Chen Wenbin's tender fingers grope the symbols on the stone tablet, a touch of tenderness flashing in her eyes, "Since he is interested in these, then... let us teach him."
When Chen Wenbin turned three, Lin Wanying and Chen Hui officially began his education.
On this isolated island, there were no academies and no teachers. The only sources of knowledge were the two of them.
"Mathematics is the foundation for understanding the world."
On the beach, Lin Wanying used a wooden stick to write simple mathematical formulas in the sand, patiently explaining to Chen Wenbin: "This is the Tian Yuan method. When you understand how these numbers change, you can calculate time, direction, and even predict the wind."
"The wind?" Chen Wenbin tilted his head, poking his tiny finger into the sand, "How do you calculate that?"
Lin Wanying smiled gently: "This is what you will learn in the future."
Meanwhile, Chen Hui was responsible for teaching him martial arts and history.
"Besides knowledge, you must also learn how to protect yourself."
Using a sharpened wooden stick as a judge's brush, he taught his son how to employ movement techniques and skills.
"Defeating the strong with the weak relies not on brute force, but on wisdom and timing."
Although Chen Wenbin was young, he already displayed an astonishing thirst for knowledge. Not only did he learn quickly, but he also often asked questions that surprised them.
Sometimes, when Lin Wanying was calculating tidal changes, he would tilt his head and ask: "Mother, why do these numbers change?"
When Chen Hui was chopping wooden stakes, he would clench his little fists and earnestly mimic him: "Father, can I hit like that too?"
Watching their son's growth, Chen Hui and Lin Wanying would often exchange glances at night, sighing at the passage of time, yet full of expectations for the future.
The transmission of knowledge, the guidance of parents.
Time flew. Although the days on the island were tough, they were also filled with warmth.
While exploring the underground palace, Lin Wanying and Chen Hui imparted their wisdom and martial arts to Chen Wenbin.
Chen Wenbin was five years old. His childhood was entirely different from other children's. He had no playmates, no bustling cities, only the vast world, mathematical formulas, and the constantly changing mechanical puzzles every day.
However, for this child who had grown up amidst trials and scholarship, this was his world.
"This is the surplus and deficit method. When you know the difference and proportional relationship between the two, you can calculate the unknown."
Lin Wanying wrote a sequence in the sand with a wooden stick. Chen Wenbin frowned, holding a tiny calculation chip, earnestly laying out the calculation in the sand.
"If the difference of five times minus six equals half the number, then..."
He whispered softly, his eyes flashing with the light of a thirst for knowledge. Under his mother's guidance, he finally deduced the answer, an innocent smile appearing on his face.
"That's right, well answered."
Standing nearby, Chen Hui looked at his son and chuckled lightly: "Just knowing how to calculate isn't enough. Here, take this wooden stick, I will teach you how to wield the brush."
He handed the sharpened stick to Chen Wenbin, teaching him the techniques of the judge's brush hand-in-hand.
"Although the judge's brush is a weapon, much like your mathematical deductions, it emphasizes precision. The point of impact must be calculated beforehand to subdue the enemy."
"If you can combine calculation with martial skills, in the future, your sword art will surpass any swordsmanship in this world."
Chen Wenbin blinked, nodding in half-understanding, then earnestly imitated his father's movements, gripping the wooden stick tightly and swinging simple attack trajectories stroke by stroke.
The fourth floor of the underground palace was even harder than the previous three. Besides tedious mathematical deductions, it also contained dynamic mechanisms and time-limited challenges.
Lin Wanying was responsible for decoding the mathematical puzzles, while Chen Hui used his strategic thinking to find the optimal path to crack the mechanisms.
This time, they didn't challenge it alone, but brought Chen Wenbin inside, letting him witness this trial of wisdom and power firsthand.
"We are not just doing this to explore this underground palace, but to let these wisdoms become the cornerstone of your future."
Chen Hui said earnestly, "The knowledge here shouldn't be buried in the torrent of time; it should be passed down by us."
After six months of relentless effort, they finally successfully unlocked the final mechanism of the fourth floor. The stone door slowly opened, revealing a profound passage leading to the fifth floor.
However, the moment they stepped onto the fifth floor, the sight before them left them thoroughly astounded.
The underground palace of the fifth floor was completely different from the previous four.
The walls were as smooth as jade, glowing with a faint blue luster. The floor lacked excessive dust, as if time had left no marks here.
On both sides of the passage were several peculiar devices. Circular blades rotated continuously, blowing an unnatural cool breeze, making one mistakenly believe this underground palace was still "alive."
"What... mechanism is this?"
Chen Hui stepped forward, reaching out to touch one of the devices. He found its material different from the stone carvings he had seen before, and it didn't even look like something traditional mechanistics could produce.
"This... looks like some kind of running device, but I completely cannot understand how it operates."
Lin Wanying carefully observed her surroundings, trying to figure out the principles behind these devices' operations. But no matter how she calculated, the design logic of these mechanisms seemed to transcend their understanding.
"Their operation is like the flow of wind and lightning."
She frowned, murmuring softly: "Could this be... the mystery of wind and thunder?"
This underground palace was completely different from the world they understood, as if it came from a much older, more advanced era.
At the core of the fifth floor, they found an ancient stone tablet. Engraved on it was a final message from an ancient era.
"If future generations find this place, please know—this is the legacy of the Wind and Thunder Dynasty."
"In the past, heavenly disasters descended, the world collapsed, floods and earth fire consumed the land. Our race exhausted the nation's power to set up several places of inheritance, preserving the wisdom of humanity, awaiting revival in later generations."
"This place stores the science of our nation, the principles of mathematics of our nation."
"The *Nine Chapters on the Mathematical Art* left by our race was originally established by scholars of the Wind and Thunder Dynasty. Future generations should know that the mathematical principles of the world all originate from here. If one can grasp its essence, they can activate the devices of Wind and Thunder."
"The final trial is hidden on the sixth floor, housing the Wind and Thunder Axe, as well as the last scientific legacy of our race. Those who obtain it can unravel the mystery of Wind and Thunder, and master the final secret of our race."
After Lin Wanying finished reading this inscription, she was speechless for a long time.
She had always thought the *Nine Chapters on the Mathematical Art* was the crystallization of wisdom deduced by ancient mathematicians, never imagining it was actually a legacy from the ancient Wind and Thunder Dynasty!
Chen Hui breathed out softly, looking towards the door leading to the sixth floor, his heart churning immensely.
"If this record is true, then... what we have found is not just the secret of the underground palace, but a forgotten history."
Lin Wanying's hands gripped tightly, her eyes flashing with excitement and deep thought: "But this also means... if we want to continue unraveling this mystery, we might spend more time... perhaps even preventing us from returning to the Central Plains."
In that moment, both fell silent.
The excitement of exploration and the longing to return home intertwined in their hearts, forming an unsolvable dilemma.