Excellent concept, very well executed too. I'm a big fan of the twist you put on the main mechanic near the end, that was delightful. The "swinging" is definitely a bit undercooked, but it's something you can get used to and for a game jam it's quite functional.
As far as suggestions go, the visual clarity needs some work: maybe try darkening the background tiles so it's easier to tell what is a wall or floor and what's just decoration; and I had a hard time at first differentiating what you can grapple and what you can't, maybe you could put a little sparkly animation on the grapple points to make them really pop off the screen.