This was tough. It took a bit to acknowledge that jump in the direction of the mouse was not just left or right, but also included up. My initial jumps were too low and I felt like I was missing something to get them higher, which I was. Once I understood the jumping mechanic I was able to progress a bit, though I was never good at it. I got the diamond on the left, and made it up to the next screen on the right. I got the first of the jump gems at the top left, but did not get to the second one, and that was where I ended it, as this is not really the kind of challenge I'm in the mood for right now.
I think the core gameplay mechanic works well. It is not necessarily something I'm going to want to play a lot of, but for this style of game it works.
It would also be nice if you did not require fullscreen to play. In Godot, you can go to Project Settings -> Display -> Window and look for Stretch. Change the Mode to canvas_items. That will allow Godot to handle the much of the resizing for different screen sizes for you.