A quick introduction to the application:

• Under the Edit menu you'll find commands like "add beam" and "add hinge."
• The left mouse button selects and drags items in the 3D view. Dragging with the right mouse button pressed moves the camera around.
• When you drag things around, you drag them in the currently selected "drag plane." The sides of the cage are highlighted to indicate the current drag plane. You can change the plane by changing the camera angle, or by choosing a new plane from the Mode menu.
• You can modify the selected object(s) by clicking on the properties in the property view window. A little dialog box will appear - enter the new value and press enter, or press escape to dismiss the dialog box without making any changes.
• Connecting two beams with a joint is a multi-step process:
  1. Create the beams and joint
  2. Select the joint
  3. Click on "Beam 1" in the property window
  4. Click on one of the beams
  5. Click on "Beam 2" in the property window
  6. Click on the other beam
  7. There is no 7. You're already done.
• Joints and beams need not actually be touching to be connected. You can have floating parts connected by floating joints. Looks weird, but it works just fine.
• When symmetric editing is turned on, all your actions will happen in pairs whenever possible. This makes it easier to build creatures with lateral symmetry, for example... well, almost every animal I can think of, with the exceptions of starfish and jellyfish.
  • Bodies and joints will be created in pairs (twins).
  • Clicking on a body or joint will select that object and its twin.
  • Changing an object's dimensions will change its twin's dimensions as well
  • If an object and its twin are selected, naming one of them "LR Object" will cause them to be named "Left Object" and "Right Object," as appropriate.
  • You can connect pairs of bodies with pairs of joints.
  • If the lefts and rights get mixed up, enter a negative X coordinate for one of them, and they will trade places.
• Joints just flop around by default.
• A "behavior" includes a motion for each joint. You can create multiple behaviors, and any set of them can be active at any time. There are two ways to create behaviors. The network behavior is somewhat documented, and the clockwork behavior isn't. Clockwork behavior is pretty tedious though, and not as flexible... I don't use it anymore, you probably don't want to either.

Use the "Play" button, or the "Mode | Play" menu item (they both do the same thing) to switch from design mode to operation mode. In design mode, there's no dynamics and you just drag individual parts around; in operation mode, the Open Dynamics Engine is running the show, and you can pull the bodies around with the mouse. It's pretty easy to fling stuff halfway to never-never-land, so be careful. I guess I should work on that.