Press S to start Use the arrow keys to move Press Z to jump and swim Hold X to run Super Mario Bros. for the NES re-created in Scratch! Regular Mario is fine, but Super Mario is currently disabled since he's really buggy and doesn't have the updated physics. He'll be playable in the future, but for now if you want to play as him, you'll have to go inside the project and broadcast the message "Grow".
Credits to @supershanio64 to make this very cool game have bugs not fix then sorry if have bugs