wtf is unitydoorstop?

Unity Doorstop is a tool that lets you run custom C# code inside a Unity application before Unity itself starts up. For modders and plugin developers, this means you can intercept and modify how a Unity game or app behaves at the earliest possible stage, essentially giving you a backstage pass to change things before the main show begins. At a high level, it works by acting as a bridge between the application's launch process and the underlying .NET runtime. Unity games typically use one of two runtimes: Mono or Il2Cpp. In the Mono scenario, your custom code runs directly alongside the game's existing code, sharing the same engine. In the Il2Cpp scenario, because that runtime cannot run custom code natively, the tool injects a separate modern .NET runtime to host your code. You simply write a standard C# program with a specific entry point, configure the tool to point at it, and it runs that code the moment the application launches. The primary audience for this is game modders and developers creating tools or plugins for existing Unity games. For example, if someone wants to create a mod that changes how a game loads its assets, redirects certain game files, or injects new debugging tools, this tool provides the mechanism to make that happen. It also includes built-in support for attaching debuggers, so developers can step through their custom code using popular tools like Visual Studio or dnSpy to troubleshoot what their mod is doing. A notable tradeoff is that because the code runs so early in the startup process, the Unity engine itself is not fully initialized yet. This means developers cannot immediately call all Unity features, they often have to intentionally pause their custom code and wait for the game to finish loading before safely making certain modifications. Despite this limitation, running first is a powerful advantage for anyone looking to deeply customize or modify a Unity application.