First of all: it is a shame that you did not put any thumbnail to your game. If I wouldnt play any browser entry of the jam I would not have recognized it. The style is awesome and I can see that you poured a lot of love into this game. I never player Hollow Knight, but what I saw from Hollow Knight looks like the main-mechanic of your game. Also I admire that you, in comparison to many other entries, actually build something fitting to the theme: by which I mean that the player is a minimalist. At first I thought I was stuck, than I tested around which buttons do what on my Keyboard and realized that I can attack. I would have been an absolute essential to write the controlls at least on the game page, because people might play the game and just quit, because they dont know what is going on. From my experience: what would even be better: but the controls onto some panel in the start area (or in a dialogue box, whatever). Secondly: I love environmental story telling and information the developer omits, for the player to be discovered. SPOILER (to anyone who is not the dev): the image showing you that you can punch spikes is a great idea, but I only saw it after figuring out the mechanic anyways by random testing (because I was like: why would someone with such great pixel art, just stop building a level?). So putting this hint a bit more into the spotlight would be a great thing (I read many comments, who just quit the game, because they were unable to figure out what to do).
In terms of the movement: the movement itself feels good, but it misses features treating the player bias: e.g. buffered jump inputs and a coyote-time. Also some of the jumps where very difficult to perform, because the space was limited and I felt like I was missing control over the player. E.g. when you put spikes on the ground for the player to bounce on, maybe it is not a greate idea to then put also spikes above the player. I like difficult games, but this is feels (honestly) unfair. But I am well aware that you tried to balance the game by placing healing items, which is respect.
This critique might sound very harsh, but I do know that this is a game jam and that time is limited. I actually wrote this, because I think that your game is insanly cool and just wont be recognized due to its missing screenshots and thumbnail.
Truly awesome work!