This is awesome for a first game! There are lots of nice little design decisions (like the MC's jump being so tiny, which really encourages using the grapple hook). The grapple hook was a great choice, and there's all kinds of neat movement tech possible there. It feels like you spent a lot of time tuning how the grapple hook feels, and it shows (it feels great to move around in). The level/puzzle design is also great. And the art and music give a really nice sense of atmosphere; everything fits into a cohesive picture.
A couple of things I would suggest (feel free to take these with a grain of salt, but just thoughts that occurred to me as I played through):
- The character felt very slippery to me, which made me feel like I wasn't always in complete control of his movements. Maybe this is intentional, but for me I generally like the controls to feel a little "tighter," so I would have made the acceleration and deceleration faster (almost instantly get up to / down from full speed).
- Restarting at the beginning of the level after death is punishing and might discourage people from playing through as far as they otherwise would. For a game like this which is really pretty challenging from a platforming perspective, I would prefer more-frequent checkpoints.
- If you were to continue developing this, I would probably turn off the lights that show where to grapple by default, but have them be able to be turned on as an "assist" option if people are having trouble (much in the same way that Celeste has a bunch of options to make it easier if you want).
All-in-all, this was a fantastic jam entry, especially for a first game! Very polished, and very fun. Great work, and keep it up! :)