The game looks great!
For some feedback:
It could have used a bit more playtesting and buxfixing.
You wont jump if you start walking and try to jump at the same time, then you only walk
The spike hitboxes are too big. A good rule of thumb is to make hitboxes on spikes and enemies smaller than the sprites, unless it can easily feel unfair for the players
The upside down character can jump while in-air.
Some more polish, this would be a great game, I hope you work on it some more, because it has potential.
Well done!