Test code doesn't validate if coin_finder returns a valid coin index, which can be used to break the tests: see this

Fixed, added explicit imports.

Fixed, user is now provided with a copy of the board to mutate as much as they wish to no effect.

Fixed. Removed the seeding function entirely and just inlined the two tests it was used for.

All tests use the same test_board object for coin_finder and coin_flipper, which can be mutated to bypass the tests: see this

The description is mediocre, could not "make head or tail" of the actual game rules

implements a ring buffer so memory usage is proportional to length of signature not n

Scala translation

Also fixes a typo in the description.

Your solution still passes i think.

EDIT: Nvm, in my screen it is still validated, yep doesnt work.

How is that related to the suggestion?

if you wrote your function using the sum of coins in a certain orientation mod size then it will work for some cases but break in others. is this what you have done?