This is just a very general question that I’m wondering about: when you have a large/complex system in your game that will take a lot of code and/or a lot of client-server interaction, how do you plan everything out so that you don’t get lost and make a bunch of mistakes?
Keep everything grouped up in folders, organize your thoughts into a word document or spreadsheet, and name everything appropriately.
Use things like ReplicatedStorage and ServerStorage properly, they’re there for a reason.
Planning
Its the most important part for a really complex system. Without planning then you’ll get halfway in and be completely stuck because you made some little part of the system not work with another part of the system, but fixing that little part breaks another part, and so on.
You have to plan
When it comes to planning itself, a good thing to use is a flowchart. It helps to visualize the entire system for you. For example, here is a flowchart of a web app I am currently working on (keep in mind this is the flowchart that I give to the public, so I made it look pretty. You don’t have to add colours or anything like that)
It isn’t the best flowchart, but it really helps you to plan what you are doing. A good website for making them (if you don’t have Visio) is Lucidchart.
look at Azure DevOps, Its also used a lot in comercial companies, you can get a free account. I also use it for version control and source control, via Visual Studio and VS Code. (after lots of planning of cause)
I use flowcharts if things get complex.