Protip: Never ever animate more than one color in a single slot. It's not worth the effort 99% percent of the time.
The gimmick of this level is invisible question blocks. The level also features a lava-y "glow" that's really just palette animation (but don't tell anybody).
The left picture is no glow, while the right picture is full glow. Everything yellow doesn't have the glow because I forgot to animate a color so now I have to do the whole thing over aaaaaaaaa, also yes there's cutoff.
As a bonus, if you'll look at the status bar on the bottom, you'll notice there's an extra 1-pixel tall black line on the top. That line was flickering. This hack is killing bsnes accuracy.