This was a fun and well rounded entry. I like the world map, it adds to the overall charm and positive vibe, and it was satisfying to clear all the stages on the map. Visuals were very clean and cute. I played through it twice :)
I can think of a few things that would make it just a little more unique and interesting. Firstly, the grapple mechanic could use some polishing; it worked fine but never really did what I thought it would. It feels like it's rigidbody based, so it might have been cleaner if you coded a simple back and forth swing with up+down shortening or lengthening the chain and just not bother with physics since they can be hard to get consistent.
I think the punching and grappling mechanics would meld perfectly if punching an enemy while midair pushed you in the opposite direction. This could add some really cool skill moments where you need to punch an eyeball to bounce off of it to reach the next grapple. I think it would've made the mechanics come full circle. And an additional visual effect or two when punching an enemy or box would've made it funner to whack stuff.
You know a game is in a good place when it immediately gives you ideas about possible additions, and I'm tempted to download the source and play with it. Great entry!