I'm glad you enjoyed it! I really appreciate you checking it out. What defines the angle is a jostle mechanic to prevent the ball from being predictable and going into a loop. I found that it was pretty effective in making the gameplay interesting and reasonably fair so I kept it.
Honestly, if I were to do it all over again, I would have made the physics specific to the ball and given the ball the ability to curve or go at a specific angle depending on how it was hit. There are times on insane where it does feel like luck because at that level it kind of is, if you don't get a good jostle.
If you want to make the ball reliably go at an angle you need to hit it with the corner of your paddle, as it will go typically go at a 45 degree angle. It was how I was able to get that score of nine on insane.