demos.compound = {};
  demos.compound.createCompoundBall = function(world, x, y) {
          var ballSd1 = new b2CircleDef();
          ballSd1.density = 1.0;
          ballSd1.radius = 20;
          ballSd1.restitution = 0.2;
          ballSd1.localPosition.Set(-20, 0);
          var ballSd2 = new b2CircleDef();
          ballSd2.density = 1.0;
          ballSd2.radius = 20;
          ballSd2.restitution = 0.2;
          ballSd2.localPosition.Set(20, 0);
          var ballBd = new b2BodyDef();
          ballBd.AddShape(ballSd1);
          ballBd.AddShape(ballSd2);
          ballBd.position.Set(x, y);
          return world.CreateBody(ballBd);
  }
  
  demos.compound.createCompoundPoly = function(world, x, y) {
          var points = [[-30, 0], [30, 0], [0, 15]];
          var polySd1 = new b2PolyDef();
          polySd1.vertexCount = points.length;
          for (var i = 0; i < points.length; i++) {
                  polySd1.vertices[i].Set(points[i][0], points[i][1]);
          }
          polySd1.localRotation = 0.3524 * Math.PI;
          var R1 = new b2Mat22(polySd1.localRotation);
          polySd1.localPosition = b2Math.b2MulMV(R1, new b2Vec2(30, 0));
          polySd1.density = 1.0;
          var polySd2 = new b2PolyDef();
          polySd2.vertexCount = points.length;
          for (var i = 0; i < points.length; i++) {
                  polySd2.vertices[i].Set(points[i][0], points[i][1]);
          }
          polySd2.localRotation = -0.3524 * Math.PI;
          var R2 = new b2Mat22(polySd2.localRotation);
          polySd2.localPosition = b2Math.b2MulMV(R2, new b2Vec2(-30, 0));
          var polyBd = new b2BodyDef();
          polyBd.AddShape(polySd1);
          polyBd.AddShape(polySd2);
          polyBd.position.Set(x,y);
          return world.CreateBody(polyBd)
  }
  
  demos.compound.initWorld = function(world) {
          var i;
          for (i = 1; i <= 4; i++) {
                  demos.compound.createCompoundPoly(world, 150 + 3 * Math.random(), 40 * i);
          }
          for (i = 1; i <= 4; i++) {
                  demos.compound.createCompoundBall(world, 350 + 3 * Math.random(), 45 * i);
          }
  }
  demos.InitWorlds.push(demos.compound.initWorld);