Documentation about "left-offset" syntax?

Where do I find more documentation about the left-offset syntax in spark?

Specifically is there an elements reference for "left-offset" syntax?

EDIT: The syntax seems to be like pug(formerly known as jade).

The only documentation exists in the github repo, and yes you're right, the files are suffixed with .shade because it used the jade syntax as inspiration. You should be able to figure a lot of it out from there and by looking at some example of its usage:

• https://gist.github.com/loudej/2371061
• https://github.com/loudej/sake/tree/master/src/Sake.Library/Shared