Overall a really good demo and it shows that lot of effort has been put into it.
My honest feedback would be that you need to think more about gamer experience and how they feel when they're playing your game. Another thing is you need to polish out a lot of things. It might feel like they're minor things but they contribute to overall gameplay experience. Please take the criticism postively; this is a great attempt at making a game and I hope you continue to make this.
Here are some of the things that I found you could improve:
1. Inconsistent art in the game; For example, in intro, some scenes are 2D, some are 3D. This breaks continuity and makes the game look unpolished. Those weird red blob enemies look out of place. Make all the art in the game 'feel' as if part of the environment.
2. Instead of asking to press enter, associate tutorial steps with actually doing the stuff mentioned and detect it. For e.g. if you're saying that 'Left Ctrl' is used to crouch, resume the game once user has pressed those buttons. Also, button's name is 'Skip' which confuses the player whether you want to skip the tutorial or does it mean resume the game?
3. Needs more animation frames to make animations look smooth. e.g. Crouching
4. 'Store' (or 'Inventory'; that's the general term) needs better interface; I didn't realize where the health upgrade was until I closely looked at it.
5. Camera moves too slow compared to some of the actions. Your character goes out of screen when performing actions like falling or running at couple of places.
Try playing some other platformer games on here so that you get a feel of what it should feel like.