1) It should show your wpm as your playing or at least between levels. If it also showed your ranking compared to other players that would provide some cool feedback.
2) I played up to level 20 and got bored. How long is it going to go? What's the reward? What's my score?
3) Changing the scenery as you progress would help aleviate a bit of the boredom. Change the color of the ships. Change the background. Change the song. Add different sounds etc.
4) your banner isn't responsive :) http://imgur.com/Dq4PCkh
5) the odd background image makes it look like something is broken on the site
6) This is hacker news. Where is the bot that gives me the high-score!