This is the 2 worlds demo of Technicolor Mario World that was released at the 2020 Winter C3.
In this hack every palette is limited to red and green like in old color movies from the 1910s to the 1930s. This hack has the same plot as a regular Mario game.
The demo goes up until #2 Roy's Castle. Also, in this demo, the vanilla bosses were replaced with custom bosses and also the hack now has custom music!
This version fixes the issues that N450 (on Discord DMs) and TickTockClock (on the C3 thread) mentioned.
(Edit: The flashing arrows when indicating a reset pipe or door were causing glitches for some reason, so they don't flash now).
(Edit 2: The walls in Lemmy's battle were acting as tiles from the large castle stone block (they were inserted as direct Map16), and resulted in Lemmy's balls going offscreen. They now act as cement blocks, and as a result, the reset door was removed (and the message block about this bug)).
Graphics and music are good and the design gets pretty decent by world 2, but it has too little going on to set it apart from your other hacks, which are all very similar to each other too. You should definitely try harder to mix things up and try out different design philosophies.
I also didn't like the referring to your other hacks on various occasions but that may just be me.
3/5, reccomended for those who like generic Mario design.