Boni: Here's an example. Set up two Primitive props on screen, like a Box and a Ball so you can tell which is which. Use the mouse to move them apart. Doubleclick on each to get the Parameters and Properties box. Select properties, and in each one check the Collision Detection box. Then click the fourth ball on the upper right of the main document window, and choose Collisions On. After that, use the mouse to move either of the props; you'll see that it stops neatly when it bumps into the other prop. But C-D only works with mouse control, not when you move the object with parameter dials. Also, you can turn on C-D for an entire Figure by the same method: select the Figure and check C-D in its Properties box. Note that C-D only works between objects that have it turned on, so you can leave some objects free to merge.

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