Ooooo boi, this OW sure is scary, well done! Chilling music.
I also liked your little introductions (title screen, intro screen and "a letter"), ok I'll try it out without save states.
...The beginning of the level is very, very difficult. It is like a try and die until you know the exact move to draw. I am supposed to jump and trigger the Thwomp, then cross the spiked platform and avoid the second Thwomp, then avoid some spikes again...
I don't like this first part because the jump done to trigger the Thwomp to fall has to be powerful enough, to fall back on the first platform... It already is an exercise. I dunno, maybe you could have put this platform just one tile to the left, to smooth things up.
Be careful with these rush levels, I've been stuck at speed 64 with jump disabled multiple times, it's a common glitch and it's unbearable.
Edit : OK, I get the concept, I almost made it to the first pipe...
I was not pleased with this design experience, it is a tad too suprising and rushed for me, give us a breath please sir. But it is good overall so good luck.