*Hearts.* A hearth is a sort of fireplace, iirc. Anywho, the gear shapes just have to be polar inversions of one another, so I'm sure it's possible to have a pair of identical, roughly heart-shaped gears.
The creative constraint of being functional gears somehow makes them even more beautiful and fun. I'm reminded of the animator Chuck Jones, who embraced what he called "disciplines", such as a Road Runner who doesn't talk, or Marvin the Martian who talks but doesn't have a visible mouth. When carefully chosen, he argued, constraints on your art can actually improve your creativity (for details, an old video about Jones is on the channel Every Frame a Painting). Anyway, these clever gears remind me of that principle. We don't always have to choose between art or engineering. Sometimes engineering and art create a virtuous cycle of improving each other. These apparently simple fun gears are an example. I wonder how they could be extended into something even better.
