Here's the score I got playing this the first time – I made it to level 25 before I was bs'd out of my last word after the text was blocked and was hit by the pieces previous to that word:
Z-Type creates various enemies that approach you until you completely type their word. When you begin typing a word, you must complete it to begin another one. This tends to be difficult when you have multiple words and several getting close to you. Some of the enemies offer counter-attacks and fire off random letters. You aren't required to type them all, but some of them can hit you. The next strong word fires off smaller words that look like little missiles. those you must type, as they do target you. Each level you finish gives you a slight pause before dropping in more enemies, much like Galaga.
There are some caveats to the game, however. The text is small, at least for me. Trying to distinguish "i" from "l" and on occasion, "a" from "o". Also, the words have a tenancy to overlap each-other, which blocks you from seeing that you are typing – which is what killed my first try at the game. I couldn't see what letters I was supposed to type when it was blocked by letters that were spewed out.
Final Score: 8 / 10
Z-Type is a free and entertaining typing game, that is… if you can type quickly and don't mind looking like you're hacking in a movie (see here).
Try out Z-Type Here: