public static abstract sealed class Sandbox.Screen

You can create variables and commands that you can run from the console.

Each camera has a HudPainter that can be used to draw onto the HUD. You do this every frame, in any Update function.

If you want to access lighting information directly you can use this.

ScreenSpace::Trace provides functionality for tracing rays in screen space to compute effects like Dynamic Reflections or any kind of ray in world space. It leverages hierarchical ray marching for efficient performance.

Sometimes you know what you're looking for, but you don't know where it is.

When creating a component there are a number of methods you can override and implement.