Tip: Remaking levels from other Mario games is strongly discouraged, especially popular ones (World 1-1 from SMB or SMB3, for example), as their over-presence in Mario games, official or not, often makes them uninteresting to play.
As the name implies, this is a pure vanilla hack - it contains absolutely no custom stuff (aside from custom levels, of course.) No custom palettes, no mixed tilesets, not even tiles placed through Direct Map16 Access, just pure level design.
Because of that, it's possible to port the whole hack over to SMA2, which is what I did. The file "PureVanillaHack_SMA2" should obviously be patched to a clean SMA2 ROM.