While the above figure appears to be a sequence of nested squares, it actually consists of a single square spiral.
Continuous Line Illusion
See alsoNested Polygon, Polygonal Spiral
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ReferencesSeckel, A. The Art of Optical Illusions. Carlton Books, p. 29, 2002.
Referenced on Wolfram|AlphaContinuous Line Illusion
Cite this as:
Weisstein, Eric W. "Continuous Line Illusion." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ContinuousLineIllusion.html