Hello! First of all I am very new to Minecraft Modding and have recently dropped MCreator because of its limitations. I've known Java for years but I never quite understood how Minecraft Modding works. I do know some really basic stuff like Items, Blocks, Foods etc. I've found some good tutorials on modding to use but none of them cover my very specific topic.
I want to be able to make a Custom GUI (which I have 0 idea how to do) and make it open once whenever a player creates a world or joins a server for the first time. The GUI I want to make has you select one out of multiple options (which is mandatory so the player wont be able to ESC out of it) and that option be stored in a variable for the rest of the world's life span. Think of it as a "Choose your character" screen similar to other games.
I would like if you could explain to me how GUI design works and where I need to place all my classes and other files to make it. I don't know if having a block entity or an entity type is mandatory but if it isn't please tell me how it's done.
I'm doing this all in Minecraft 1.18.2. If this question has been made before, sorry for reposting, I could not find it so please direct me to it. Thank you all in advance!