Start with framing. It is a very tight screen space and the player is quite large.
Next, look into pacing with your scripts. Keep the pacing consistent regardless of framerate. Objects that randomly speed up are unavoidable. This is an important part to learn that even AAA programmers forget sometimes, but can easily ruin a game. 4/5 tries the black rock(?) on the right will fly towards me faster than the jump can move me out of the way.
Try using a simple music making program. Make a basic beat to set the theme of the game. It doesn't need to be good, it just needs to be yours.