I really liked the two different phases and how they played off of each other. Picking off a single just-turned zombie out of a crowd of people is so satisfying. I also enjoyed that during the "work" phase, you need to rapidly scan the room for people thinking about brains and you don't have to be careful about where your character is exactly. You're moreso looking for a path where you can boost all the people who are turning. That contrasts with the "break in" phase where you need to be mindful of the paths available to you to get to an ammo case or drop, and your eyes are more focused on the area immediately around the character.
I would have loved to see some bonuses that improved your abilities during the "work" phase, as the powerups largely just affect your power during the "break in" phase. Maybe a move speed or slowing down the rate at which workers turn into zombies? Also felt like the bullet collision was a touch too small, but that also feels like it could be a meaningful design choice.
Thanks for this excellent submission!