I had them spawning far away so the player wouldn't see them pop in, so I made them quicker so you wouldn't be waiting so long. Definitely not the right approach.
If I had to make it again I'd have a less open space and have slower zombies spawning around corners you can't see.
I agree, UI was definitely lacking. I left UI and menus until the end of the jam, but ran out of time. Something to add extra time to next jam for sure