/closed string

closed🔒 string (more accurately, closed coil) :== a string state with no open🔓 circuitry (does not have endpoints; forms a loop➰).

All game-related strategies (goals) are devised to obtain a closed string (thereby solving and validating it as some fibor, although the game itself may still be open) via folding. (see zero-bubble, loop➰)
/// Actually, there is no loop➰ requirement for a string to be closed (not open), since the end of the string must attach to a (mem)brane (even if that membrane is the string's other endpoint). Therefore, the yield is derived when in that a string is closed, but only by acoustic approximation.