I thought this was really good! The visuals and audio did a really great job building atmosphere and both were incredibly well-done!
I thought it was funny that it tells you this game is "easy" (it wasn't).
It seems close to being a very professional indie game. I would just recommend a few minor tweaks:
1) It appeared that the phrases were purely randomized. On my first play-through, I got 3 long phrases back-to-back right off the bat. I think a more enticing progression would be to have stronger-slower zombies start further away with longer phrases and weaker-fast zombies pop-up with single small words. That would give a mixture of fast-paced action and slow burning tension.
2) I felt like the unconventional capitalization was forcing me to fight muscle memory (eg: "Coming from the Ground" - I never would have capitalized "Ground" in this phrase). Personally, I would have preferred to either leave out capitalization entirely or just keep it to the first word of the phrase.
3) I would have liked to have an audio cue indicating when I made a mistake in typing. I have a sticky keyboard and coupled with the restart penalty for mistyping a letter, I was killed off in the first area. After that, I found myself frequently glancing down to at my keys (something I rarely do in normal typing), so a "mistake" sound would have been helpful.
4) Maybe they were there and I missed them, but I would have liked to see health items strewn around that I could type at to pick-up. It would have added a sense of choice to mob moments if I had to pick between typing at the things hurting me or the health to save me. Without that kind of choice incentive, I found myself relying almost entirely on the autotargeting system.
Seriously, GREAT JOB! I don't usually bother with detailed feedback like this unless I think a game has a lot of potential - and yours certainly does!