SMM2 is basically a level creator for Super Mario Bros. 1, Super Mario Bros. 3, Super Mario World, New Super Mario Bros. U, and Super Mario 3D World. You can make and play millions of levels from creators across the globe. Levels span from traditional, to platforming, Kaizo, puzzles, troll levels, and more. You can do a custom search for levels or do Endless Mode which gives you a set amount of lives and throws different levels at you to beat. You can also play multiplayer co-op or vs with people on the internet.