Where to begin; the game is very barren. I'll try to break this down for you, but as it stands now, i understand you stated that you know it's simple and that you're learning, so i'll try to be as concise and constructive as possible.
Art: Quite simple, not too bad actually, i would simply suggest making the walls black rather than blue, and having it so that the restart screen looks a tad more professional by keeping the game screen there with a simple "Score=xyz" and "restart" button in order to really improve it. Another tidbit is that the ball starts to spaz out after a few bounces, i don't know the cause, but that definitely needs fixing as a graphical bug.
GAMEPLAY: The game is extremely simple, you know that though; the issue i feel being presented with the gameplay is that there is absolutely no reason to get higher scores. There's no reward for it, there's no over-arching goal to it, there's nothing enticing someone to play it. As such, I would definitely recommend some form of goal or reward system that would help make it worth playing, something as simple as "get to a certain amount of bounces, pass a level/gain a medal" would work.
The use of simple level design like obstacles and something like maybe a "destroy the objects on screen by aiming the ball a certain way" would definitely enhance this game.
STORY/PLOT: There isn't any; these games don't really need a story per-say, but something as simple as "destroy objects while bouncing the ball to get points/rewards" would be enough, as explained in previous note.
MUSIC/SFX: There isn't any. As i've played your *Mase* game, I'm aware you can put music in, and i think you did a decent choice in that game with your music, so i'm disappointed you didn't add anything in, nor did you try to show improvement in that section of skills. It comes across as a lazy decision to me, and i hope to see you try harder in the future.
Overall, a very simple game, not bad, but definitely not hitting that level of entertaining. I think that these games are also quite done and dusted, so i don't know whether i'd mark it high even if you did it well. But as it stands currently, it lacks too much substance to me, and generally needs a lot of improvement.