Godot 4: Night vision shader (tutorial)

Hi everybody! During the development of our point-and-click adventure game Whispers of Prague, we played around with the idea of creating some scenes in complete darkness, so the main character would need to acquire night vision goggles to navigate the scene. This idea was eventually discarded, but the effect itself isn't entirely bad, as you can see right now. Let's take a look at how such a shader works.