my solution by using a stored list of primes: 15/40615/28

I think the size fits the problem quite well. In general, if the problem needs like 5/6 MC's or more, I don't think you want to push it too hard by making it too small. And as your scores show, it's nice and fun to have some extra room to optimize something so power hungry.

As for the shape, I like it. It's always good to make it more interesting than the default shape or 'the box'. Sometimes just one notch can make a puzzle a lot more challenging and fun.

So, well done!

I haven't tried to optimize (yet) but got a 15 / 40627 / 29 .

I would love feedback on the shape; it's pretty haphazard. I made it wider as I worked until I could get a solution. I wonder whether it's a little too wide for the general difficulty of puzzles in the game (or, alternatively, whether it guides towards a specific solution by being too inflexible).

My designs:

46,257 power ￥１８ (35 LOC) - fits easily
28,900 power ￥２２ (45 LOC) - tight fit, but I was basically tweaking the dumber one and certainly could've finagled harder (lots of wasted space due to bad pinout alignments).