I'd like to experiment with the CAP output file and write a little program to use the data in the CAP file for my purposes. I guess, there exists some file format documentation? Where can I get it?
Develop games in your browser. Powerful, performant & highly capable.
There's no documentation I'm afraid - and it's a big binary file - but you can make deductions about what is written through the source code functions where data is saved. Apart from that, there's no overall guide, it's done programmatically. Construct 2 will use an XML format, so it will be much easier and more self-describing so tooling should be more straightforward.