Uses the Wii graphics engine to recreate the look of pixelated 8-bit and 16-bit Mario games. Multiplayer Support:

It’s a fan-made ROM hack of New Super Mario Bros. Wii (released in 2009). Hacks like “Retro Remix” typically redesign levels, graphics, or mechanics to give a nostalgic feel, often incorporating elements from earlier Mario games. These are created using unofficial modding tools and require a legitimate copy of the original game to run.

This looks like a deep dive into the New Super Mario Bros. Wii: Retro Remix