Hello, I could talk a lot what I liked about this preview but I assume you get that a lot since your product is amazing. However, flaws are more important to game developers, right? In my humble opinion, most of the preview was flawless, but these are the things that drew my attention:
1. No sounds in main menu. (not even a flaw since it is pre-alpha)
2. Optimization. I made some stuff on Unity too and the FPS was not great too, so I guess it is the Unity engine itself. But again, it is not a flaw because even a low-tier can run it without a problem. The only thing I am mentioning it is because I am currently using a laptop (not the worst one tho) and I am getting ~20-30 fps when there is a lot going on, yet some top-tier games like Overwatch runs 60+ fps. Yet again, this is not even a flaw just worth mentioning.
3. When I was shooting the pistol the raycast from the gun was way off the zombie (the cursor was right on him) but the bullets still hit them. Thought that it is worth mentioning too.
Some of my thoughts may not even make sense and I am sorry for that, but feedback is feedback, right?
I really hope seeing this game released ASAP. Thanks for creating it!