Mechanic endlessly amassing troops in the apocalypse

[A fake mechanic, lacking resources, forced to live as an undocumented immigrant.] [A real mechanic, using machines as an army, wielding power in a chaotic world.] Li Fei transmigrated to a resource-depleted interstellar planet, fortunate to be taken in by the owner of a repair shop, but his future was bleak due to his undocumented status. Until he awakened a two-way teleportation array, he discovered that the other end was a monster-infested post-apocalyptic wasteland—the Land of Calamity—which was also his treasure trove of opportunities! When the path of a mechanic became intertwined with the two-way teleportation array, his survival plan was completely rewritten: learning knowledge, accumulating resources, and hoarding skills in the interstellar world, building a solid foundation in mechanics. In the post-apocalyptic wasteland, he gained experience, hunted crystal cores, cleared zombies, and stockpiled massive amounts of supplies. While other mechanics repaired junk, he summoned an army! Psionic mechs cleared the way, automated robots wiped out enemies, and heavy-firepower mechanical arrays covered the battlefield—one man was an army! From an undocumented immigrant in a desolate repair shop to a mechanical overlord spanning two worlds, Li Fei used steel and cannonballs to forge his own legendary troop-building empire between the post-apocalyptic world and interstellar space! (Double Door + Mechanic + Post-Apocalyptic Survival + Interstellar Adventure + Mechanical Army)