I Can Level Up in the Apocalypse

The apocalypse descended. After a torrential rain, zombies overran the Earth! Song Yan, reborn in the past, unexpectedly gained a sign-in System and surged ahead from then on! While everyone else cowered in fear of the zombies, Song Yan charged straight into their midst! While people fought tooth and nail over a single firearm, Song Yan seized an entire arsenal! By the time everyone else came to their senses, Song Yan had already become a legend!