Thanks for playing the game!
Yeah, I need to differentiate this game from others, but for a prototype, it seems to be working well.
The red enemy actually doesn't do damage. I added this at the last minute to add some more flavor to the game, but it was definitely rushed and not how I saw it in my mind. I think I will end up making it one tap the player though as it is pretty easy to defeat with the spawn delay. However, it doesn't give that spooky element I hoped for.
For the health bar, you start with 200 HP, which means you can survive 6 zombie hits that deal 100/3 per hit. I intentionally didn't add one to clean up the GUI and make it a bit scarier/less cluttered.
The enemies that spawned in one direction from the boss are the "minions." It was intended to be like a boss fight, and the sole focus is the boss. However, to make the boss a bit harder, I added minions that would spawn to make it a bit harder than just shooting the boss. I might end up adding more distractions for the boss, but I am not sure.
I will try out your game later today when I get back.
Thanks for the feedback!