Very nice game! I think the main thing you can improve is platformer physics. The jump height is very hard to control, and it's very inconsistent. Sometimes a full jumps will be higher than another one, and it feels very luck-based. Also, if you jump exactly as you land, the jump will always be tiny.
I suppose the way you make the character jump is to apply an upward force. I think it's often better to act directly on the rigidbody's speed. Something like that:
rb.velocity = new Vector3(0, jumpSpeed, 0)
There's also this bug that lets you go through walls. But it really helped me to get a good time in my speedrun.