Hey! Thanks so much for the feedback, I really appreciate it!
There's still a lot more I want to do with the idea. The core is there, but so far I've only scratched the surface of creating situations where players need to make decisions as well as type words. For example, I'd love to add ranged enemies you'd have to pick off with a rifle, plus grenades that distract the horde, like in L4D.
I've also got ideas for new levels, like a highway where you have to escape the horde while clearing barricades blocking your way.
The clipping issue showed up after I moved a streetlight and accidentally blocked part of the zombies' path. Thanks again for spotting it!