The past week, I've had very little time for the game, but I managed to do a couple of things. First, I added a new challenge where the player needs to move upwards using the grappling hook:

I had my kid playtest it and after several iterations of tweaking the shapes and positions of the holds, it seemed like he was able to complete it without too much pain. I also shortened the challenge from five holds to just three.

In addition to the new challenge, I also tweaked the in-air behavior so that the player keeps its trajectory when they release the grappling hook. Previously, the player would almost immediately stop unless they held the left or right keys down which felt unnatural. This change also affected jump, so now jumping is less precise but more natural.

One last thing: I'm thinking of making the ground a bit more interesting. I did this visual experiment with a few ground layers at different depths in Photoshop:

Cheers!