Neat concept but pretty rough. I didn't have a strong feeling of the loop theme either (even if going through something twice is technically a loop).
Also seemed absurdly hard, I only beat the first difficultly by mining a path connecting to no caverns with enemies because I saw no way to really survive against them, they seem far far too powerful.
Also really wish the UI would not have rotated with the second character's gravity and that there would have been an arrow on screen indicating which direction is "down" when not with the default gravity section.
(The "No that won't work" with the red overlay would also frequently persist after a death, forcing me to reload the page just FYI)