Simple but very effective! There's a quiet elegance to the movement, well done. I think some sound effects / music would have been great here in addition to some particles when you hit the gray parts, etc. Maybe some more variety in the levels (powerups that you can pickup, maybe for bonus points?). Very well done for your first game though! Congrats!

Very challenging! I got stuck/stopped playing somewhere. xD

Here is my feedback:

What did I like? 

• The mechanics of the game.
• I liked the graphics.
• Excellent usage of the theme and the restrictions.

What did I dislike?

•  There's nothing that shows me at what level am I.

Suggestions

• Add a score system.
• Add music.
• Increase players' speed when I press shift.
• Display the number of the current level and the total stages of the game.
• Change the colours of the game on every level.
• Whenever I finish a level. Display "Level Complete" or something.

Definitely a super solid entry as a first game. The transitions and basic concept did what they needed to, you explained anything necessary... nice.

Keep going, making small steps! Add some sounds, visual effects, some more levels, maybe in the future even a random level generator for an endless mode. Don't overscope; continue making approachable games like this, and I'm sure you'll find your way.

This was your first game???? Hell, I was happy that my first game booted up without crashing. Having this as your first game is incredibly impressive.

Alright, onto the gameplay - simple to understand and control, you can just jump right into it. I appreciate the fact that it was multiple levels instead of one giant level - less frustration when you fail. Now, this game has a lot of ways to be improved. You have a solid foundation already. Here's a couple of my suggestions: 

• Player speed increases the more levels he completes.
• Moving obstacles
• Even more "tracks". You have 2, why not make it 4 in later levels?
• Make controls feel more "tight". IMO right now they are a bit too floaty. What that means is that there is a delay between pressing the button and the player acting on it. For example, tight controls would mean that the second the player stops pressing a button, the player stops immediately, instead of drifting for few pixels. However, the game is perfectly playable with the current configuration.

You are starting game development on a really good game as your first. Wish you best of luck in Game dev! Thanks.