I always enjoy seeing what others are working on so...
I recently got the urge to make some icosahedral (20 identical faces with each being an equilateral triangle) fidget spinners -- a completely useless result! It did afford an opportunity to, much as fenichel recently ranted about, hand generate some gcode. This improved my grasp of polar coordinates, looping, conditionals and variables as implemented in PP (LinuxCNC). All and all a fun way to waste some time while getting a small dose of understanding!