First off, I think J and K were not the right call for the player 1 keyboard mappings. The idea of Pong is moving the paddle up and down, so the keys should be one on top of the other rather than side to side. Something like U/J or I/K, or better yet W/S, would have worked a lot better. The paddle controls also felt a little slippery and imprecise.
Once I got used to that, though, I did have some fun with it and I'd say this is sort of a neat twist on Pong, though there's maybe more you could have done with it. Maybe make it so you expand in different areas depending on where your paddle is when you hit the ball or something. I also think it's cool how you get different colors each time you play.