For 10 seconds, my visual field was filled with a pattern of approx 20 x 20 small squares, each with moving content.
The upper and lower halves of the field were quite different and distinct.
The upper half (20 wide, 10 high) comprised generally red coloured squares. Within each square there were short horizontal bars of various brightness moving up and down.
In the lower half (20 wide, 10 high), all squares were filled with the same black/white star pattern, all rotating at the same speed.