1y by Trilobit demo

Public Domain.7z <1y by Trilobit (PAL) (PD).nes> from GoodNES3.14 appears to only work in Mesen and possibly RockNES (if it can be configured for PAL). Most of the modern emulators can handle raster effects, but that demo is doing something unique. It uses Mapper 011 (ColorDreams), but that's a really simple mapper.

Does this demo tap into some unusual feature of the PPU? Or, does it require extraordinary emulation accuracy?

What makes you say this is working properly in Mesen?
It looks pretty different in all emulators I tried, so I actually have no clue what it's supposed to look like.

Either way, the game seems to make some pretty odd vram writes. It actually made me notice Mesen doesn't restrict the internal values of t & v to 15 bits (though changing this seems to have no effect since the VRAM/palette mirroring causes writes to $8000+ to be mirrored properly).

I am not 100% sure what it is supposed to look like. But, my best guess is that the upper half is supposed to be wavy and the lower half just scrolls. Mesen is the only emulator that produces a stable image.

any emu working.

I do not believe that FCEUX is emulating the imagery correctly.

If it's supposed to look like that, then this is one of the worst demos ever.

I think Mind Control Trilogy took the crown as worst NES demo ever. It's even worse than that one 'demo' that consists of a photograph of someone's genitalia.

Update: Some analysis revealed that the demo accesses the PPU Data Register ($2007) during rendering. After introducing the behavior changes to the scroll registers under that condition, my emulator produces a very similar visual effect as seen in Mesen. It also fixed the glitch in Burai Fighter's score bar, mentioned in the Wiki link.

On a side note, it did not fix the shaky score bar issue in Difference. Please respond if anyone has suggestions about that one.