What to see
The blue horizontal stripes above are oblique – are they? In my eyes an amazingly strong effect.
What to do
A number of further parameters can be adjusted (within limits) to modulate illusion strength. The “CenterMarks” aren't doing anything for me. In Victoria's version there are even more such decorations.
This effect became popular in July 2017, originally designed by Victoria Skye, which I simplified a little for easier programming. It is interpreted as a version of the Café Wall illusion; however, I do not think this is correct – the mortar lines are missing here. The angle illusion is caused by the small check marks, and that effect was first demonstrated (I think) by Akiyoshi Kiatoka (my animated version here).