A variant and a combination of Hering's and Zöllner's illusion. The red grid is completely straight all the time.
Submitted as an answer to the Showcase of Optical Illusions question on TeX SX.
Click the Illusions tag below to see more!
The perpendicular lines that do not match row to row create an illusion of the lines between them being not parallel.
Submitted as an answer to the Showcase of Optical Illusions question on TeX SX.
Click the Illusions tag below to see more!