I'll hopefully be participating in this years 7DRL, and I'm wondering how much preparation is allowed before the starting date?

For context, I'll be using C# + Monogame along with engine code I've written over various different projects. How far are we allowed to prep the project before the 7DRL starts? For example, would I be able to get the user input, rendering and basic screen management code written and functional before the start date? Then once the challenge starts, work on the mechanics and gameplay of my entry.

This is my first 7DRL and I don't want to break any rules before it's even started.

Thanks!

I've done a couple now and that's exactly how I approach it.  Anything specific to the game I'll be making waits until the actual 7DRL week. But basic engine features like you describe can be done before then.