Algodoo

I call it a "zero compass" because, like a magnetic compass that points to magnetic north, this compass points to the X0,Y0 coordinate in the Algodoo world. Start Algodoo, than move the compass with the Move tool anywhere in your scene, and when you let go of it, it will point directly to the zero coordinate. You can select it and copy it and then paste it into your own scene. If you ever lose track of x0,y0, just plop this handy compass down and it will point the way!