Staring at a rectangle

The last couple of days I've been intensively looking at a black rectangle on a small table. During a usability test, users were observed while using a specific product.

[ I'm sworn to secrecy regarding the nature of the tested device... ]

Interesting shape on a table...

In the test users were asked to place the product inside the outline, allowing us to have a good view and see if everything was clear to the users. From the moment the rectangle was filled, watching it became a lot more interesting...

[ preparing for this test was the reason for my long radio silence... ]