LÖVE

Pinkishu wrote: Yeah, I wasn't asking for implementation " just if there are some kind of standardized formats developers are encouraged to use (like for some things its encourage to use JSON, or some RFC-format like IRC communication)
Or pointers at how to structure custom foramts

That's all up to you. It's less about following some format, and more about conveying to other level designers how your format is constructed. A good example of this is Tiled's TMX format.

But really, you don't even need to go that far. Tiled has to get down to the nitty-gritty since it's cross framework. You could probably just make a file format to your liking, and include an example in whatever packaging you have for your modding/level editting information.

Two logical choices are lua scripts or just plain text. The real problem is writing functions that read/write these files. If you're using plaintext it doesn't really matter how the document is structured, as the structure would be defined by the way you output data.