The bounding box is the natural implementation because it matches what the user sees -- when you select multiple objects, the rotation handle is at the corner,

The bounding box is the natural implementation because it matches what the user sees -- when you select multiple objects, the rotation handle is at the corner, because where else would it be? Plus it’s very easy to code and to test. But yeah, using a rotationally-invariant point would be better than the stateful fix the article goes for. Center-of-mass would make sense except it might do strange things if you have a mix of solid shapes and lines. How much mass should the lines have? Using the centre of the bounding circle is probably best, as others in this discussion have suggested.