Hey, very nice site.
also how do I build buildings? How do I stack walls ontop of each other and make roofs? I have never figured it out.

To raise any scenery objects, hold down the Shift key (I'm not sure whether it's the right one or the left one, I think it's the right one...) and move your mouse upwards to raise it off of the ground. The same applies to roofs.

thanks very much! Nice site once again!