This game is pretty good, and nails what a metroidvania is about. The pixel art is crisp and well implemented. I like the background and subtle parallax. I appreciate that it runs in browser. Unfortunately, it was just a bit too hard for me, so I wasn’t able to make it very far.
I think the controls could be improved. For example, you could make it so that the space bar closes the tutorial windows, instead of forcing the user to reach for the mouse with 2 hands on the keyboard.
Overall, I am most impressed by the pixel art.