Two new things mostly for the PIXELART:
1. Shadows: Instead of using fading shadows, use only 3 different greyish to black colors and use these as tiles for the shadows (e.g. for the top tile of ladders) to keep the pixelart a little more consistent. This tutorial might help to show what I mean:
(Seems like this forum messes with the link. just copy the full line.. the page is hosted at archive.org)
2. I got to the "fire end-boss" for the first time. Is it true, that the treadmill is changing directions? If yes, the animation of the treatmill should clearly indicate the direction through animation AND there should be a two second indicator, that the direction will change soon (flashing maybe?).