I agree with Dalton's suggestion of a cool down of some kind, or maybe even a limited amount of "fuel" that each player can utilize at a given time (that then recharges over time), and they could decide to do small shots or charge up for bigger shots. As is, you've created an interesting two-player experience that has variable possibilities for play, especially given that the ball can bounce in multiple directions. I did notice that at larger sizes the ball is much harder to influence, and so maybe once it reaches the size of the "arena", the point/round resets. Another thing that might be interesting to experiment with is that instead of just being able to shoot at any time, you could trade shots (so each shot becomes really consequential).
Scripts were well-organized and commented - thanks!