These are simply circles arranges around a circle over regular intervals. Different size of circles and different intervals create different patterns.
Once you have all these circles, taking out arc segments in a regular way can create beautiful patterns. Think about how this one is done.
img srcAgain, take out areas can create different effects.In this one, you replace arcs by lines to create a different effect.
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This spiral design is done by taking out all arc segments of one orientation.
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