Mkay! So some things I noticed:
- As 8enB noticed, the double jump inputs are a little sketchy. I think it's probably best for the second jump to be active at any time during the jump arc, rather than just after the peak.
- When the key hits the top of the stage, all of its horizontal velocity is immediately cancelled. I don't think it's necessarily an issue, but it made some segments of the game a little less intuitive. In "Seems a Bit Easy", I noticed sometimes this happened with a left throw at the top without jumping. It wasn't consistent, so it's weird that the physics seem a little random. But for me, this actually happens pretty often. It seems to be well over 50% of the time. I imagine the intended solution to this room is to just carry the key, but throwing the key can be an option - if you get lucky. x3
- I have no idea if this was intentional, but in the last level, picking up the key to cause the wall to appear on top of you has some interesting interactions with the player.
- Similar to the above point, it is possible to throw the key into the ceiling, for example, in "Seems a Bit Easy." It's not game-breaking. Just funny.
- The choice of Ctrl and Space for the left hand is a little tricky; I held my index finger over space and my little finger over Ctrl, which did start to be a thing after a while. I imagine you'd want to change this for more playability, especially as the game gets longer. ^^
- EDIT: I'm noticing that with spike hitboxes... is there an invisible pixel to the left of the visible spike that's part of the hitbox? If so, that would explain some of the fun I had trying to figure out the fourth level ahaha.