I must say... this is probably the smallest file size of the custom campaign I've played so far, with the unzipped vpk file only 90.1MB, primarily due to the minimal resources used, mostly a white background with black lines, the overall map is incredibly solid, all five chapters have the infinite zombie wave event, the first two chapters are generally easy, but the bridge to the safe house in chapter 3, the final area in chapter 4, and the finale rescue point are incredibly challenging. Now I finally understand what the author meant by "This campaign is deliberately designed to be hard." As far as the normal difficulty of playing this campaign is concerned, the author has indeed met his expectations for this campaign!XD
Simple... but hard as hell!