Really cool little game, enjoyable for a few minutes though not much more. I really like the idea that to beat the enemies you have to push them off screen, tough I would like for them to fight a little if it's not hit squarely in the middle.
A somewhat minor complaint is the interpretation of the limitation. Though I understand that it would feel dry for the player not to move, recoil is technically a way to move.- It doesn't really matter, so it isn't the thing holding it back. Other possible complaint is the enemies pushing you off screen, but the limitation is "you area immobile," not "you are immovable," so I don't particularly mind.
The main thing holding it back is the lack of scaling of difficulty, one moment playing feels like the previous one. From what I've played it seems like if you take the points off there would be no way of telling if the game is several minutes in or it has just started.
Difficulty scaling could help with the monotony, and having enemies get pushed back less when hit on the side, but if hit squarely in the center getting pushed way back, would give it more oomph, that could be accomplished by letting them fight back the push instead of spinning and floating off screen. Other enemy types would also help, maybe one that is faster, but moves in bursts, one that resists push a lot more but is slower and lingers at times, one that moves erratically to try to dodge your attacks. All of these enemies could be more frequent the longer the player has lasted, that would give it more spice.
All in all, a good submission to the jam.