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What: This illusion delivers a striking impact, presenting a checkerboard pattern where each corner features a small diagonal cluster of checkers with an alternating design. This specific arrangement, which inverts the black and white squares, begins to warp your perception, creating the impression that the lines, particularly near the edges, appear slanted rather than perfectly vertical.

I initially encountered this particular effect on a blog named Revolution Analytics, where the author was generating visual phenomena using the R programming language. My adaptation is a JavaScript implementation of the same core concept, enhanced with a few modifications such as animation and the option to pause it at any moment.

How To: Simply fix your gaze directly on the image and attempt to convince yourself that you are looking at perfectly parallel lines. You can also click anywhere to halt the animation and observe the static illusion. After viewing it in motion for a period, the paused version can feel particularly disorienting.

Explain It: This website features several optical illusions that employ a comparable technique, including the spirals and the straight line squares. Based on my research, these illusions typically utilize a configuration of either offset or angled squares. As your brain attempts to interpret this visual data, it makes assumptions based on recurring patterns or structures commonly found in nature, leading to a misinterpretation in this specific, artificial context.