Global Catastrophe: I Use Black Tech to Build a Super Shelter

He has only been transmigrated for half a month when the apocalypse arrives! Staring at the red alert, Li Tian nearly crushes the sofa. He had just planned to copy a novel and coast to victory, and now the world is about to end? Luckily, he activates the Doomsday High-Tech System! He digs out a 4,000-square-meter underground shelter in six hours, welds the walls with memory alloy, reinforces them with a space-expansion gun, and makes them capable of withstanding meteor impacts and nuclear radiation. He unlocks a cloning pod that produces three top-tier special forces soldiers a day. With a super 3D-printing machine at his disposal, he can print any missing parts in an instant! After a meteor shower, the entire world freezes over, radiation spreads, and order collapses. Li Tian stocks up on food and fuel with his clone squad, but while searching for supplies, he stumbles upon three sisters who are freezing to death. Should he take them in and form a team, or defend his fortress alone? In the apocalypse, strength is what counts!