Gridmonger Manual

Advanced usage

Command line usage

If you start Gridmonger from the command line, you have the option to override various window related settings or to use a different config file. This might come in handy for power users who want to use a script to start an emulator and Gridmonger side by side.

Please run gridmonger -h to see the full list of available options.


Options requiring a value need to be specified in option:VALUE format, e.g. to set the window size to 1200×800, you would use --width:1200 --height:800 (or the shorthand -W:1200 -H:800).

Map file format

Gridmonger maps have the .gmm extension and are stored in the generic RIFF container format. One of the reasons for this choice was admittedly nostalgic; I wanted to honor the outstanding Interchange File Format (IFF) invented by Electronic Arts and Commodore for the Amiga in 1985, the greatest personal computer of all time. It’s a great hierarchical container format, as evidenced by its many different incarnations and derivatives (WAV, AVI, PNG, JPEG, WebP, just to name a few).

The details of the map format are described in fileformat.txt in the GitHub repository.

Theme & configuration formats

Themes and the configuration are stored in a very minimal subset of the HOCON configuration format. Currently, there is no exact specification for this — if you want to write these files by hand or would like to manipulate them programmatically, just follow the syntax and structure of the existing files and you’ll be fine.