Here is a hack which combines: Mario Bros., Super Mario Bros., Super Mario Bros. 2 JPN (The Lost Levels), Super Mario Bros. 2 USA, and Super Mario Bros. 3.
Also added into this hack is the ability to use SRAM to save your games and to save your top score in Mario Bros.
Featuring a fresh set of vivid, newly themed worlds, The Rainbow Realms is a complete 8 world hack, with level design aimed to emulate the style and creativity of the original SMB3. The difficulty curve is aimed at the average to good player of SMB3, though there are some challenging levels and a couple of difficult puzzles in the last few worlds.
The aim of the project is to modernize the look of classic Super Mario Bros while remaining within the limits of the original programming and ROM size. There are no ASM hacks and no expanding the ROM–and no mapper! Just brand new pixel art (and a few things borrowed from later Mario games), palette edits, and metatile rearrangement. You can enjoy the original game with a fresh coat of paint, or try combining it with map or gameplay hacks that don’t change the graphics too much!