The pixel art looks great. The sound effects and music work well together and feel consistent. I think the character design and overall feel of the game.
Some thoughts:
- The grapple mechanic is pretty fun but it took me a really long time to get a feel for it. Seriously, I think it took me 20 tries to get out of the area with the grapple gun. (I'm not great at platformers, but maybe the timing with the gun is too precise or something). Also the gun seems to always turn me to the right for some reason.
Great job!