After loading Level 19, documentObjectMadness.js, the game screen turns completely black. All input seems to be ignored, but sound still works.
If I hit "Reset", I can see my character (green) in the top left and a different character (red) in the bottom right.
Is this the expected functionality? I have not found anywhere in the code window that can be edited, so I'm not sure how I might progress on this level. In case it matters, I am using Firefox 28.0 on Windows 7.