This is where my patterns start to intertwine the straighter edges and square features of the latter half of the set and the circular focus of the first half. The curves are created in your mind by this focus on the dark and light corners of the squares. I designed this effect based on similar illusions, but it took a while to perfect the spacing etc. This is the code I had the most trouble with as it used modulus loops and the PDF export refused to accept such things, so this version is longhand and slightly larger scale. I will upload my green version using modulus' as well.
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Make your updates, then upload your tweak!