The problem with being reincarnated into a medieval fantasy world wasn't the lack of Wi-Fi. It wasn't even the monsters roaming the borders.
It was the draft.
Arthur von Pendelton, third son of the Iron Duke and currently six years old, stood in the center of the nursery. He was undeniably cute—silky black hair, large emerald eyes, and cheeks that the maids couldn't stop pinching. But behind those eyes lay the mind of a man who had once optimized global logistics networks for fun.
He glared at the window.
It was a masterpiece of stained glass, depicting the First King slaying a Wyvern. It was majestic. It was historical.
It was also single-glazed.
"Thermal conductivity is a joke in this kingdom," Arthur muttered, his voice high and childish.
A semi-transparent blue screen hovered in his peripheral vision.
[Civilization System Online] [Observation Detected: Poor Insulation.] [Heaven-Defying Understanding Triggered: You have analyzed the molecular structure of Sand and Mana.] [Blueprint Created: Double-Glazed Tempered Glass (Mana-Reinforced).]
Arthur nodded in satisfaction. The System was helpful, but honestly, he could have figured that out himself. The System just saved him the trouble of doing the math on paper.
The heavy oak door creaked open. A giant of a man stepped in. Duke Kaelen von Pendelton looked like he ate boulders for breakfast. He had scars, a beard that could hide a badger, and an aura of terrifying power.
Behind him was Duchess Elena, a woman of grace and soft smiles.
"Artie!" The Duke boomed, his terrifying aura vanishing instantly as he rushed over and scooped Arthur up. "My little genius! The maids told me you were staring at the window. Do you want to go outside? Are you yearning for the battlefield?"
"He's six, Kaelen," the Duchess chided gently, walking over to pinch Arthur's cheek. "He probably just saw a bird."
Arthur tolerated the cheek pinch with the stoicism of a saint. "Father, Mother. The thermal retention of this room is sub-optimal. The heat loss through the fenestration leads to a 15% increase in firewood consumption. It is inefficient."
The Duke blinked. He looked at his wife. "Elena, what did he say?"
"He says it's cold, dear."
"Nonsense! I'll have the guards burn down the forest and triple the firewood!" The Duke declared, brimming with doting enthusiasm.
Arthur sighed, a tiny hand resting on his father's massive shoulder. "No, Father. Efficiency. We do not work harder; we work smarter. I need sand. And a fire mage. Preferably one who can maintain a steady 1400 degrees Celsius."
The Duke's eyes welled up with tears of pride. "He wants to play in the sand! And he wants to watch fire! A true Pendelton!"
Two hours later, Arthur stood in the estate's training grounds.
The family's court mage, an elderly man named Gandolfi (no relation to the grey wizard, though he wore a similar hat), looked confused. He was one of the most respected fire mages in the kingdom. Usually, he was asked to burn goblin camps or create grand displays for festivals.
Today, the six-year-old Young Master had asked him to melt a pile of sand in a stone trough.
"Young Master," Gandolfi said, leaning on his staff. "Are you sure about this? Magic is a dangerous force, not a toy—"
"Focus, Gandolfi," Arthur interrupted, holding a strange metal tube he had ordered the blacksmith to bend earlier. "Your flame temperature is oscillating. I need a steady burn. Blue flame, not orange. Eliminate the impurities."
Gandolfi frowned. A child lecturing me on mana control? He decided to humor the boy. He intensified his mana. The fire turned a scorching blue.
[Heaven-Defying Understanding Active.] [Analyzing: Tier 3 Fire Magic.] [Optimization Complete. You have deduced: Combustion Engine Principle.]
Arthur ignored the notification. He watched the sand turn to molten glass. "Now, flatten it. Use the wind spell Zephyr's Touch, but modulate the frequency to create a pressing motion."
"Modulate the... what?" Gandolfi asked.
"Just push it down flat and hold it steady!"
The mage did as told. To his surprise, the combination of his precise fire and the wind pressure created a sheet of glass clearer than anything the royal artisans had ever produced. It didn't have the bubbles or waviness of standard glass.
Arthur wasn't done. He made a second sheet. Then, using a thin frame he'd designed, he sandwiched a layer of dry air between them and sealed the edges with a mana-conductive resin.
"Done," Arthur dusted his hands off. "The Pendelton Thermal Pane."
Gandolfi stared at the glass. He could see a fly buzzing on a leaf fifty yards away through it. It was invisible. It was perfect.
"My lords..." Gandolfi whispered, looking at the Duke and Duchess who were watching from the balcony. "The Young Master... he has revolutionized alchemy in an afternoon."
"I don't know what al-kimmy is," the Duke shouted down, grinning, "But look at that glass! My boy made the clearest window in the world! We shall install them everywhere!"
Arthur nodded. Step one complete. Now I can sleep without a draft.
As he admired his work, a small girl peeking from behind the training pillars caught his eye. It was Lily, the daughter of the Head Knight. She was clutching a slightly wilted flower, her face red, staring at Arthur with wide, sparkling admiration.
She walked up to him, trembling, and held out the flower. "Young Master Arthur... you... you were amazing! This is for you!"
Arthur looked at the flower. Then he looked at the glass. Then he looked back at the flower.
Ah, Arthur thought. She has noticed the lack of flora in the training ground. She is suggesting that my industrial efforts are disrupting the local ecosystem.
"Thank you, Lily," Arthur said seriously, taking the flower. "You are right. Industrialization must be balanced with environmental preservation. I will design a hydroponic garden next to offset the carbon footprint of the furnace."
He patted her head and walked away, already mentally drafting blueprints for a greenhouse.
Lily stood there, clutching her chest, her face steaming. "He... he wants to build a garden... for us?"
[Mission Complete: Create a Modern Material.] [Reward: 500 System Points.] [Side Note: User is hopelessly dense. +10 Charisma anyway.]
Arthur swiped the notification away. Dense? I'm solid muscle and bone. The System is glitching.