Nothing special
The framerate was too low, you could have used 30 fps instead of 10 or 20? Change the fonts, make the ball nicer looking. The gradient blocks weren't that good looking either. Add background music and sounds of the ball hitting the blocks. Add some originality, nobody wants to play the normal Pong, it's boring and everybody has done these kind of games. Blocks' hitboxes were also messed up. If you really want to make this kind of game again, add something that no one has done before, I liked the idea that it was in space, perhaps add some meteors or something?