I like that you made everything from scratch for the jam. The game is rudimentary, the graphics looks decent, and it's good you have background music. Great job for your first game! What matters is that you made and published a complete, finished game.
The ladders are weird to use. Jumping on enemies could feel much better than how it is now. I recommend having the enemy die the instance the player jumps on it, and playing a sound and particle effect.