I think the theme will be approachable by most. It might take some creative thinking, but it doesn't require the most polished graphics or advanced techniques. However if you can do that, that's great.

Unlike the gigantic PGD Annuals we did, the PGD Challenge is meant to be a much smaller task or "challenge" where even a partially completed game has a chance to stand out. And fun too. Not that the big compos weren't, but these you can start em and leave em if you don't want to stick it out with a long project.