Nit: it's jarring that when I first mousedown on the control, the value changes. This makes small, incremental changes difficult. Now, if I click on an area of the circle that is far from the pointer, perhaps it should snap. But if I'm close (or on top of the pointer), snapping is undesirable. (compare to a physical knob, which is the thing being emulated here: touching the knob does not change the input, you must to…
I actually thought that part was kinda nice in allowing me to make either quick large changes or small incremental changes. But then again, I'm not your average interwebs user, so I probably would be aware of the same issue if actually implementing it.