10 element center_x { text }?,
11 element center_y { text }?,
12 element angle { text }?
18 attribute mass { text },
19 attribute inertia { text },
20 element fixed { empty }?
28 element data { coordinate+},
29 element offset { coordinate }
35 element point1 { coordinate },
36 element point2 { coordinate },
37 element radius { text }
43 element offset { coordinate },
44 element radius { text }
51 element event { text },
52 element script { text }
56 coordinate = element pair