I have included a how-to on angle adjustment, as I forgot to add it. See above in the controls section.
Adding it to the docs is always a good idea indeed. I did notice I could influence the angle by moving the paddle before already. However, it is different from what I'm used to with these breakout type of games, I would expect the place where the ball hits the paddle also influences the angle. However, it's your choice of course, just wanted to give you that feedback :)