With the inventory management system gradually taking shape under Zhao Yi's meticulous coding, the small group of survivors started to feel a bit more organized. However, the perils of the post-apocalyptic world were far from over.One day, while Zhao Yi was still fine-tuning the system in their makeshift shelter, a commotion arose outside. A band of raiders had spotted their hideout and were approaching with malicious intent. The survivors panicked, not knowing how to defend themselves against these armed marauders.Zhao Yi quickly sprang into action. He realized that they needed an early warning system to detect threats like this in advance. Using his knowledge of software and a bit of the remaining electronic components he had gathered, he began devising a plan.He decided to create a perimeter monitoring system. By connecting simple sensors that could detect movement and sound to a small computer, he could write a program that would analyze the data from these sensors. If the program detected unusual activity within a certain range around their shelter, it would trigger an alarm.He explained to the others how it would work. First, he would calibrate the sensors to differentiate between normal movements like those of small animals and the approach of human threats. Then, the program would constantly monitor the sensor data in real-time. When it detected a pattern that matched the characteristics of a potential enemy, it would sound a loud alert.The survivors watched in awe as Zhao Yi got to work setting up the sensors around their shelter. He had to be careful, as the raiders were getting closer. With some quick soldering and coding, he managed to get the system up and running just in time.As the raiders neared, the perimeter monitoring system did its job. The alarm blared loudly, giving the survivors precious moments to prepare for the confrontation. They grabbed whatever weapons they had managed to scavenge and took defensive positions.Zhao Yi, though not a fighter by nature, used his wits. He hacked into an old communication device he had found earlier and managed to jam the raiders' rudimentary walkie-talkies, causing confusion among them.The ensuing battle was fierce, but thanks to the early warning and the element of surprise they gained from Zhao Yi's software-based interventions, the survivors managed to fend off the raiders. As the dust settled, they looked at Zhao Yi with newfound respect and gratitude.This victory gave them a boost of confidence, but Zhao Yi knew that they would face even greater challenges in the future. And he was already thinking about what other software solutions he could come up with to keep them alive and help them thrive in this harsh new world.