I sadly disagree with the other comment saying that this plays well. Imho, there are 3 major problems with the gameplay:

1. The hitboxes are janky. If you're not centered horizontally over an enemy's head when you land on them, you're the one to get hit. Also, if an enemy fires a bullet horizontally at the exact moment you jump on them, you kill the enemy but get hit by the bullet. Not being able to jump on enemies during your invincibility frames from getting hit is also weird.
2. The enemies are unpredictable. Having unpredictable enemies is not in and of itself a bad idea, but if that is the case, the player need to have time to react no matter the move the enemy does. Here, you can try jumping on an immobile enemy and right after you jump, the enemy suddenly also jump towards you and there's nothing you can do to avoid it. This is made even worse given the jank of the hitboxes. Meaning even without jumping, just the enemy moving at the last moment is enough for you to be the one to get hit.
   It seems like the enemies are some kind of record that loop? That would explain the weird teleports.
3. The sprint is slippery. In and of itself, it's not a problem, the same applies to Mario games as well. The difference is that when you reverse direction, you don't accelerate fast enough, so you don't change direction fast enough, and as a result, for example, you overshot platforms. Without sprinting that's fine.

this is a wonderful game! the sprites look so cute! and the game plays well and is obviously the classic engaging gameloop of mario, a very simple yet excellent execution of a classic Idea that I am yet to see another one like it in the jam, well done on the theme relevancy!
overall a solid entry, great work!