An unofficial level and world map editor for the game The End is Nigh, by Edmund McMillen and Tyler Glaiel.
The editor provides the necessary tools for modders to unpack the game's resources, modify and create new levels, and modify the world map, all with an easy-to-use interface.
For those interested in contributing to the editor's development, building the executable is as simple as running one of the available build scripts. All of the code dependencies and external third party libraries have been included within this repository, so there is no need to fetch them manually.
A version of Visual Studio with C++17 support is required. To build the editor run the build\win32\build.bat script. To modify build parameters and
flags open the build\win32\config.bat script and tweak the values to change how the editor is built (e.g. release or debug mode, 32-bit or 64-bit).
The project's code is available under the MIT License.