There isn't any special handling for MacaOS, the keys should be the same across platforms. Arrow keys, enter, control and whatever SDL returns for SDLK_ALT which *i think* on a Mac keyboard is the option key. If you have a mouse with two or three buttons you can also use the right mouse button for jump instead of alt and the middle mouse button for picking up items instead of the enter, but you should be able to play the game with just the keyboard.