Fun concept and setting! It's very hard to get into it though, could use a more interactive tutorial.

I liked the idea for this game! Skateboarding while fighting off enemies sounds like an interesting concept, and some of the mechanics felt pretty good.

I had a really hard time managing the controls. There are a lot of things you have to do at once and the platforms are too far apart to really get a hang of it. I have a couple suggestions:

1. Make the platforms more frequent at the start of the game. You can spread them out further later, but at least while I'm getting used to the controls, I need the extra help. 
2. Add a little bit of explanation when things happen. I think a Tony Hawk-style trick counter would be great! I was bouncing off the rails (without grinding) and didn't register that wasn't what I was supposed to be doing until I read the controls. I bounced up, so I thought that's how it was supposed to work.
3. Flying through the air seemed a little weird. I would have expected to be on the ground while skateboarding. That's not really something you need to change, but it could help with #1 if you made the game take place on the ground and procedurally added obstacles.
4. Finally, the control layout is the opposite of what is usually seen in games, with no method to change it. Usually, you move with WASD and do actions with the other hand. This made it harder for me to play than it otherwise would have.

All in all, great job for your first project! I definitely see a lot of potential here.