Each zombie comes with a three letter word attached. For some reason it never goes beyond three letter words. If you type that three letter word, you shoot the zombie - usually. Sometimes it misses, so it doesn't always matter if you can flawlessly type and kill every zombie on the screen, you will likely die anyway because your shots just happen to miss the one zombie that is within arm's reach. That's what happened to me, and I missed him twice! This removes the pure skill element, and in my opinion, removes the feeling of personal challenge as well because it could be the game's fault that you lost, not that you couldn't type fast enough.
Another issue that has been pointed out by other players and will probably fixed soon is that the words sometimes appear beneath another zombie, which makes it really hard to type them because you don't know what they are!
He deserved to die, he was a lousy shot anyway!
Personally, I just don't like zombie games, so I probably won't be spending much time with it. The whole missed shots thing drives me nuts anyway. But its still worth a try if you're into this sort of thing. I do like the way the game solves the problem of being unable to see what the next word is, since all the words are present on the screen ahead of time. You just have to choose which one to type next.
Note: As of the latest version, the issues with words being covered up has been corrected, words longer than three letters will appear, and shots no longer miss. Happy zombie blasting!