Extremely Cold Space and Time: from Underground to the Universe

Lin He was hit by an energy bomb and traveled back to three days ago. At that time, alien civilization had not yet invaded Blue Star. But because it was three days ago, when he was ready to mess up, he suddenly awakened a system called "Hengzhe" and obtained a stardust belt and a super shovel. But he didn't expect that some events in this world were disrupted. Alien civilization arrived early, the sun disappeared, and extreme cold came... What about him? I had no choice but to stay in the underground city for the time being, which was a shelter created by human civilization through desperate efforts. Lin He will use the system to lead mankind to defeat alien civilization, regain the earth, and move towards the universe... [P. S.: There may be some weapons or other things in it that I made up at random.