The platformer controls are nice and it overall feels smooth.
There are two things I noticed though:
1. The left enemy walks to the right, turns around and then walks on until infinity. Maybe have him move left and right constantly like the one on the right
2. The background. You already have a background that can be scaled endlessly to the left and the right, so make use of that. The top and bottom can just be filled up with colored rectangles.
While I encourage you to make another game as you said in you description, I'd suggest you first try to make more of this game. The main reason I suggest this is so you can learn to stick to one project for longer and maybe learn to plan ahead more in the future. If you notice your code can hardly be altered now, this can be a lessen for you in the future. Even if it is easy for you, you learn to go back to code you have written before and make changes.
No matter which you do, keep at it and don't stop learning. I'd be happy to play either the updated version or your pong in the future!