Scrollable windows! That's the big accomplishment for the past two days.  I certainly wasn't planning on implementing them when I started, but it was just too tempting.  Not surprisingly, it took a lot more work to implement scrollable windows than any other GUI component so far.  Still, they're done now, and I'm happy that I put in the time.  They're going to be absolutely crucial for complex games.

Oh, and those are checkboxes.  They're not too interesting - only took about 5 minutes to implement, since they're really just handicapped progress bars (at least, that's how I see them).