If 58 is your highscore I think that you didn't use the wave bomb (holding key until letter bar is full and then release). Also if the key is pressed avoids being hurt by letters. This is something that a lot of people missed and that I should have explained in the game.
I recommend you to try it because it REALLY improves the gameplay, if you have some troubles there is more information about it and a video showing that in the game page. Sorry about that. Anyway I am glad you have a good time.