I found the concept of paying attention to the shadows really unique and creative, and I think this project can grow into something really big!
I only had two issues:
1 - In my opinion, the camera is placed way underneath of where it should be, as half of the screen is being occupied by the ground. Placing the camera higher up, or placing the levels into a lower height would make the game less "claustrophobic", giving the player more space to look at and to you more space to build different kinds of levels!
2 - I think there could be a "Restart Level" key in the pause menu, because there is a level in which you can get stuck if you jump over a certain wall, making you having to restart from level 0 again!
Not your fault though, as making a whole game all by yourself (including the music!) must have been really tough!
But yeah, after I finished your game, I wanted to play more levels, which means I really enjoyed the gameplay!