Cute game! I really nice the parallax background. And an original OST for the game? Always a nice touch!
A few comments to add what Levrault said:
I didn’t realize at first that you could go into the area with the green background near the start, since it’s the same colors as the walls, so I only went on the down path. That might be easy enough to address, I think using two different shades of green for walls and backgrounds would work really nice.
Also, I ended up making it the end at one point with 11/12 coins, then realizing I couldn’t backtrack since the jump to go backwards was too large. I’m not sure if I just missed something and there was another place I could’ve gone.
Overall though, great job for your first game with zero experience!