Nice! Just finished it. There's quite a few grappling hook games this jam, but your take on it is quite refreshing. I liked the use of the different surface types. And I have to admit I was skeptical of the use of a 'slow time' mechanic initially but it became very useful later on.
To improve how it feels, I'd suggest decreasing the size of the colliders on the spike sprites. It'll help the player feel like they weren't cheated if they just nicked past the spikes but still got detected as being hit.