Doom 64 for Doom II is a vanilla recreation/re-imagining of the Doom 64 maps. They are made with [mostly] vanilla assets and can run in the original vanilla Doom (and Chocolate Doom). The goal was to recreate the major aspects of the maps while allowing for creative liberties where needed or wanted. There are lots of new graphics, some new textures (like skies), some new music tracks, a couple of new monsters, and minor enhancements for folks who play in advanced ports (like GZDoom).