While the grapple physics are finicky at first, once you get familiar with them, they are pretty fun.
I think the level's design could be changed to accomodate for the grapple.
I think using the right mouse button to retract the grapple instead of allowing the player to press the left button to send it and release the button to retract it is a strange solution.
It's kind of hard to built momentum by bunnyhopping too.
In terms of graphics, perhaps the game's terrain would benefit from having more contrast and overall being more gritty, like in its thumbnail.
Also, I think you could include some sort of minimap, so the player can see where the hidden items and other goals are. You could also take a sort of "compass" approach, like in Fortnite.
Maybe the game's music should be more dynamic and punchy to compliment the gameplay.
Other than that, it's a pretty good game.