Okay, this is driving me crazy. When you open the tile editor (Builder's Forge) the default camera angle is top down looking from directly above. How do you change the camera angle so you can actually see what you're building?

I know it can be done from looking at Brad's video the other day but he doesn't mention how to do it. I've tried everything I can think of, clicking and holding the middle mouse button, both mouse buttons, holding the right mouse button and dragging, cntrl+left+drag LMB, cntrl+RMB+drag etc.

For the love of god, someone please tell me how to do this one simple thing.