Welcome to Hell. An insanely difficult Game Mod of Super Mario World, Kaizo Mario World (literally, "Hacked Mario World", but also translated as "Asshole Mario World") is well known for being the Trope Codifier of the Platform Hell genre (well eclipsing the popularity of earlier examples such as Jinsei Owata no Daibouken and the then-unnamed Super Mario Forever), and for being the game that launched a lot of LPers' careers on YouTube. You can get the original Kaizo here and Kaizo Mario World 2 here.