Boony

Hiya, I know this has been done already but I'm new to modding and only have any experience with plugins, I want to make a sideways mod, like the videos, where the world essentially seems flipped sideways. I understand its probably just flipping the camera and player model sideways, along with flipping the gravity as well but, being new to this, i have no idea where to even start. I have everything set up, the jdk, intelliJ, forge, etc, but I honestly dont even know what to do next. I know this is such a noob question but i feel like as soon as i get my foot in the door the possibilities will be endless and I just want to try this. Not a java noob, just dont know where to even look in the documentation for this info. edit: some clarification