I agree with traveler to an extent. I think that a compo that would focus on just cross-platform would be a little restrictive but given enough time it would allow for some learning experiences also.

I don't speak for anybody else but I tend to need a purpose for having to learn something to actually do it. Otherwise it won't get done.

I also think though that a broader rule set will bring more into the compo. But it would be feasible to add to the score of someone if they did actually make it cross-platform.

anyway these are my ramblings on it.