These doodles are mostly for stress relief for me plus training my hand after the time of many wrist inflammations due to strain. They were made from 2016 to now.
When I begin such a doodle I have no plan. All I know is that it will follow some rules how the edges are connected and what angles are allowed. So the doodle would just grow like a crystal. As you can see they also may vary in symmetry and number of axes - which also might be broken sometimes in favour of other patterns. That's what I call them, "Muster" - German for "patterns".
I usually do these on 4-5mm squared paper. Some were made on a thin hexagon isometric 5mm grid or dot grid. Some are made colourfull by pencils including ones in neon and metallic, markers or just plain ink.
Images which go with my Extra Fine Nib Ink Review (EFNIR) posts. (Reviews of inks using only a Japanese EF nib.)
Images with a file name ending in capital "AP" show the ink on absorbent paper. Above the black line is puzzle paper (like thick newsprint), while below is old 20lb copy paper. Images with a file name ending in a capital "S" show a scan (rather than photograph) of the ink.
A file name with no code-letter in the file name, just the ink name, is a screen capture of the review from the video. A file name ending in a capital "Z" is a "zoom" photograph taken with a USB microscope. A file name ending with "W" (possibly followed by a number), or "WT", indicates the results of a water test. A file name ending in "LW" is a microscopic photo (at 100x) with a scale showing the line with in microns (micrometers). A file name with "Smear" at the end is a microscopic photo of the ink spread on a slide.
Occasional extra files may include ones with a "C" (or "Chroma") at the end of the file name for the results of chromatography. Others will have descriptions added to explain what they are.