In The Machinery, everything is a plugin. You can extend, modify or replace existing engine functionality with your plugins.
The Engine explicitly aims to be simple, minimalistic, and easy to understand. All our code is written in plain C, a significantly more straightforward language than modern C++. The entire codebase compiles in less than 30 seconds, and we support hot-reloading of DLLs, allowing for fast iteration cycles. You can modify your plugin code while the editor or the game runs since the plugin system supports hot-reloading. In short, we want to be "hackable." Our APIs are exposed as C interfaces, which means you can easily use them from C, C++, D, or any other language with an FFI for calling into C code.
Guides to follow: