I can't get past the door where there is a button, a diamond and a rectangle thing in the cave in front of it, and I noticed the music - which is nice -  fading away the farther you get away from the starting point. I guess you have used an AudioStreamPlayer2D instead of just an AudioStreamPlayer. That also explains why I can hear the music only on the left channel.

I like the visuals, the seemingly randomly placed objects in the background add a lot to the flair.

The physics needs some work, though. In the cave which is stuffed with movable blocks the blocks got stuck. Changing the direction of blocks does not always work, and sometimes multiple of them change direction at the same time.

Regarding the score: there's an exploit. You can just grab some valuables, reset the level by pressing R and grab some more, and do it until you grow tired.