Comments by themissingpawn

I meant that chess engine programming is too hard for me in general. I
naively thought that I could copy & paste a few lines of code and make some
minor alterations. But I can't understand a single line of the code that you 
posted. I once created an application that played Connect 4 (in Java). But
that was quite a few years ago, and even then I didn't understand it (it
was a copy & paste job - even at the time I didn't understand how minimax
works). So I think that is why I overestimated what I was capable of. But
the truth is, this is beyond me - so I'm giving up on this project now.
btw I just want to say that Fairy-Max (in XBoard) was one of the first
chess programs that I played after switching from Windows XP to Linux, and
I still play it occasionally (it's a good Latte Chess opponent for me
too)... so thanks for that :-)

Thank you H. G. Muller for your input, I am always happy to receive feedback and ideas. The king double move to c2/g2 is interesting, however I feel that the king may not always be too safe on those squares, mostly due to the number and power of the bishops. e.g say the king double moves to g2, and then later the g2 and b7 bishops trade off. Now the king is rather vulnerable on g2, and whites queen does not want to get lured onto the a8/h1 diagonal, as blacks other white squared bishop might immediately spring into action.

Also I don't want to give up on Luft Castling just yet! I agree with what you said about the location of the rooks, but I have found through testing (without special castling) that the luft manoeuvre sometimes tends to happen naturally (manually). It seems to have some advantages, that would be even better if sped up. This is sheer luck, as I can now see that there was a distinct lack of sophistication in how I decided to include it as an option (i.e. "okay so let me find something that is like castling, but with an extra rook"!). It has the advantage that it immediately accelerates the development of 2 rooks, while moving the king to a safer place behind some wing pawns and the luft rook. It seems counter-intuitive, but somehow it seems to work, at least from my very limited initial tests.

I'm not discounting the double king move idea either though (I would prefer your first option - i.e. 2 steps to g2 subject to f1 OR f2 not being under attack). I feel it definitely needs to be tested along with the other ideas. And it could even be included along with luft castling and normal castling. I still have a lot of testing to do, which will be much easier when I can I find a way to modify an open source chess engine to include these features.

Thank you! I have to say that Sjaak II looks like a very nice program, that
I hadn't come across up until now - and so far I have found that it works
beautifully with XBoard. The source code looks fairly easy to navigate too.
I'm trying to pluck up the courage to start tinkering with it, so that I
can implement double castling - although I fear that I may also need to
start modifying XBoard, and quickly find myself way out of my depth. But
out of all the open source chess engines I have looked at so far, this
could just possibly be one that I could do something with. And even if it
is beyond me, I'm sure I will have fun playing with it!