Sightly is the new HTML templating language introduced with Adobe Experience Manager 6.0.
This is the Sightly Specification that defines the syntax and the behavior of the language.
A Java-based reference implementation was donated to the Apache Sling project and can be checked out from https://github.com/apache/sling/tree/trunk/contrib/scripting/sightly.
The Technology Compatibility Kit can be run on implementations to check their compliance with the specification.
An implementation of version 1.1 of the language specification will be made available in AEM 6.1.