This looks very nice. I like how you are considering stuff like how to not make the "charge" thing abusable. Perhaps like the "landing" after the jump, you could also put a similar thing at the start of the jump- like how a person bends their knees first.
You could have it so that if you tapped the jump button, you'd jump a little instantaneously, but if you held it down, your character would bend their knees further, jumping upon release of the key- of after a maximum time is exceeded. The power of the jump would be more the longer you held the jump key.
Hella impressive how you are doing this so fast.
Edit: I watched Day 10.