Building Up Steam is done.
Windows binary is here. Source is here. The Windows dist I tested with Wine (I don't even have Windows), but I don't expect a problem.
I'm mostly satisfied with the features, and definitely like how it looks. I'm a bit disappointed with the breadth; I would have at least liked more than one kind of enemy and more interesting levels.
I'd like to give a big thanks to richard everyone else running this contest. And good luck to everyone else, and hang in there.