Here's is a ruleset that I fell in love with immediately, it's very unique and intuitive (even if lengthy). Get those gears turning! Shade some cells so that each orthogonally connected area of shaded cells forms a cog: a shape reflective symmetry on all axes (horizontal, vertical, and both diagonals). Cogs may not be orthogonally adjacent, but must all form a single diagonally connected network. The network of cogs must be functional, meaning there may not exist a loop consisting of an odd number of cogs. Circles must be shaded, and mark the center of a cog. No 2x2 area may be entirely unshaded Solve on Penpa+
