Thank you for playing and rating!
The spike colliders and fireball frequency are on my list of things to fix after the jam. What did you mean by jump buffering, though?
Jump buffering allows the player to press jump slightly before landing on the ground so that they jump immediately when they land. It's very easy to implement and improves the game feel. Googling it should bring up lots of tutorials.
Aha, yes! I know what you mean. Thank you!
(Not sure if you noticed, but I did implement a bit of coyote time. I'll consider jump buffering also.)