The level design is great. I had a lot of trouble trying to beat some of levels but they were definitely the fun kind of challenging. The base mechanic and the way it's used are really cool, I feel like the fact you can grapple multiple points is sorta useless tho unfortunately. Since you can't decide which to ungrapple from it means you just end up ungrappling from all of them rather than the one you wanted to.
I feel like making it so you could ungrapple from them specifically based on which one would definitely help that. Another thing though, which was very much helped by the time slow, is the accuracy you need to hit the anchors throughout the levels. I feel like maybe making it a little easier to hit them could help? Just to help avoid times where you just barely miss the grapple.
One.. "bug" I did run into though was a little "bounce" sometimes when I would ungrapple or be grappled that ended up with me dying basically every time it happened. I'm not sure if that was intended or just a side effect of the physics but it was definitely kinda annoying... but once I figured it out I managed to get past it.
For a first jam though, great idea, great mechanic and pretty awesome execution. I'd definitely be interested in seeing more levels!! Especially with those bouncey blocks! Which I honestly thought were going to be falling blocks.