Great concept!
Most of what I want to say was pretty much nailed by horbror. The main problem is that you get to defeat enemies, heal, and move to other rooms by typing them... but that's pretty much it. As cool as that is, you may need to expand upon it. Once I realized I had caps lock on the whole time (lol), I got bored of the gameplay pretty quickly. Try to make something early on that the play can be hooked by... maybe an upgrade, a boss fight, a story throughout...?
Dude you HAVE to make this an educational typing game, schools would love this.