It did take me a little while to work out that the left and right edges were pinned, and my drag-and-drop didn't do what I intended more than once. But... then

It did take me a little while to work out that the left and right edges were pinned, and my drag-and-drop didn't do what I intended more than once. But... then you're being tested (unintentionally) on the ability to discern that too, I guess?