A pretty simple aperiodic monotile found in 2022 and published in SMCG2023. The shape alone ensures that every tiling of the plane you can build from this tile will be aperiodic. In this sense it has the simplest matching rules imaginable. This one is not really a substitution tiling. However, its properties (e.g., being an aperiodic monotile) are deduced from related substitution tilings, see for instance Hat Metatiles. The exact relations are rather tricky for this particular one.