I think the ideas here have potential! I do have a few suggestions which IMO would have made the game a lot more fleshed out:
Some form of indicator as to what the next thing is (Platform, jump circle, shot) would have helped gameplay quite a bit, IMO; showing the current shot and the next would allow the player to have just enough information to strategize.
At the moment, the character stops as soon as they touch a wall. I feel like it would be nice if rather than stopping, the character turned around and kept bouncing back as though he had hit a level wall.
The levels start when the game starts and keep looping, so like 1 -> 2 -> 1 -> 2 etc. I think a title screen to take you to the first level, and an end screen card after the final level indicating the end of the game and which may take you back to the title screen would be helpful to bring some intro and closure to the game. The title screen also provides a nice place to introduce the goal and the platforms.
Some simple animations when a platform or bullet is shot would have added a lot of polish to the game IMO. Something like a short fade, zoom, fade/zoom, or fade/fly in would have been perfect.
The art as it is is fine, but very plain. Some textures for the platforms, and maybe animations for the character, enemy, and jump platform, would have also done a lot to the eye candy. The music was there, but it’s fairly plain. I think a slightly longer tune would have helped. The sound effects present are sufficient. More could be added but what’s there right now is fine.
Of course, after that, adding some more levels (especially some more challenging ones) would be all that’s needed to have a solid game!
As I said, I think this game has a lot of potential. I honestly encourage you to consider fleshing it out after the jam!