code: function (params) {
          return new hitagi.Entity()
              .attach(new hitagi.components.graphics.Graphic({
                  anchor: {
                      x: 0,
                      y: 0
                  },
                  relative: false,
                  z: -1000
              }))
              .attach(new hitagi.components.graphics.Rectangle({
                  color: params.color,
                  height: levelHeight,
                  width: levelWidth
              }));
      }
docs: Define entities.