Time passed quickly, arriving at the year 351.
This year marked the tenth year of the apocalypse.
The number of newborns in G City's underground city reached over 20,000.
And the first batch of children would be starting elementary school this year.
Due to increased lifespans and the fact that the age gap in G City's underground city had been filled, the number of children conceived through artificial wombs gradually declined.
Now, the population of G City's underground city was nearly 150,000, exceeding its design capacity.
Therefore, Tang Li undertook another round of expansion for G City's underground city.
She purchased a giant residential module and some cultivation and planting modules from the official channels, expanding the first level.
Meanwhile, Tang Li was also secretly digging underground.
From the fourth level downwards, she excavated a lot of soil and rock, collecting it and removing it from her space.
Then, she installed fluid containment magnetic field equipment, injected fluid, and replicated a large number of storage modules.
Before she died, she would replicate items from her space and fill these storage modules with as much as she could, leaving them for Song Chaoyang and Tang Chenxi.
As early as December 348, Song Pinxuan had developed the Body Enhancement Potion and the Mental Enhancement Potion.
Based on the second generation of substance X, he further weakened it to develop the Body Enhancement Potion, which only enhanced physical strength and muscles, and the Mental Enhancement Potion, which only enhanced mental power.
Over the next two years, these two potions had been sold to major underground cities.
Especially the Mental Enhancement Potion.
Because it could significantly boost people's mental power.
Upon receiving feedback signals from the brain-computer interface, users would no longer fall into a deep sleep quickly due to insufficient mental strength.
Therefore, even though both potions were very expensive and could only be purchased with G City's underground city's point vouchers, many people flocked to them.
Even the official government transported large quantities of metal ore, selling them as scrap to the G City underground city's exchange for point vouchers to buy the Body Enhancement Potion and the Mental Enhancement Potion.
Previously, after the criminals used to build the underground city and tunnels had all died, the authorities were struggling with how to continue construction in environmentally harsh areas.
The use of the Mental Enhancement Potion finally provided a solution for the authorities.
By enhancing mental power, people could remotely control wireless brain-controlled robots, engineering mechs, and other brain-controlled devices.
As long as wireless brain-controlled robots or engineering mechs equipped with quantum signal receivers were manufactured, remote construction could be carried out without any casualties.
Over two years, the authorities had extended the underground tunnels to the extreme north snow plains and the western seas of the Yellow River, transporting vast amounts of mineral and oil and gas resources back.
By exploiting these resources, the four underground cities of Z Country now possessed almost inexhaustible energy.
With the problem of harsh construction environments overcome, the authorities also began to expand the underground cities.
In addition to expanding the existing four major underground cities, building more residential modules to alleviate housing shortages, more cultivation and planting modules to produce more raw materials, and more storage modules to store more supplies, new underground cities were being constructed along the underground tunnel routes.
This greatly expanded humanity's living space.
Regardless of the natural disasters that occurred outside, they could not stop humanity's progress in building their homeland.
By continuing to develop underground tunnels in the west and north, Z Country would eventually connect to the major oil fields of Country O and Country Y, and even extend to the west and south of the great deserts, connecting the entire Eurasian continent.
While Longcheng and Shancheng were fully focused on developing westward and northward, Jiangcheng and Haicheng also turned their attention to the sea.
Land-based natural resources were abundant, and so were marine resources.
Moreover, the ocean offered protection through its ice layers and water surface. Although the seabed ecosystem had been severely damaged, the species had not completely gone extinct.
With the protection of the ocean, underwater cities and tunnels could be built, and the marine world could be developed!