Very innovative! I love the concept and the design of these levels is quite stellar. I see a lot of potential for more interesting levels and design mechanics here and I'd love to see you continue down that road.
One complaint I have is the input for flipping the blocks - it's annoying to have to click a specific point for an action that doesn't really require precision. I think just clicking the left mouse and being near a block should be sufficient for flipping the world. Also, as much as I wanted to finish Speedrunner and Hardcore modes, I ran into a few bugs that prevented me from progressing.
Overall a really well done game that has a few kinks