Originally Posted by fromelette

Looks like you're using Firefox with zoom. If I use it (crtl + mouse scroll up or ctrl + "+" or view -> zoom) I get the same black space that you get due to Firefox being unable to stretch flash ratio. The screen size you're seeing is this game usual display size afaik. To reset zoom in case you want to do so, use ctrl + 0.

That isn't the case either, I'm using Firefox at 100% (no zoom). Tried resetting just in case in and nothing.