Here’s one of the disappearing blocks that I forgot to post earlier. I’ve already cut it into nine equal squares. When you rearrange the pieces you can make a churn-dash. Churn-dash is the name of an old quilt block. If you looked at a butter churn from the top it might look like this. I think the dash is the part that moves up and down to churn the milk into butter. Here is a churn-dash with a pinwheel in the middle.
But you could rearrange the pieces so that the churn-dash was grey and the background was the purple dotted fabric. Or, you could change it into sort of a wagon wheel or wedding ring, with a pinwheel in the middle: