I really felt like the world was ending! It would seem quite difficult to have a game that goes from easy to hard while the number of mechanics decreases each level, but the way you did it made a lot of sense; a great example of intentional game design.
If I had a complaint, it’s that grayscale is really hard to read and I stopped before the end because it wasn’t so pleasant to look at. The beeps in the silence were also a little piercing. While I think those changes were part of the game’s design, maybe they were a little heavy-handed in implementation (and affect accessibility to a high degree).