This is such an impressive piece of work. I really love the art style, first of all. I like having the option to change the look of it too. The implementation of the score board is really cool too for sure. I found the shield pattern mechanic to be interesting, although, it was very difficult to rotate the shield, while simultaneously trying to defend the planet. Rotating with the keys might make for a quick fix, if that's something you decide to do.
Nice game, keep it up!