The maze is always solvable when mirroring is off. Every spot is reachable in the maze. With Shortcuts at minimum, there is a unique path. With Coverage at maximum, that path touches every 2x2 block. When generated, the maze contains 2x2 blocks with the top-left corner always solid. It is then expanded by the Hall and Wall size to alter the appearance. Mirroring breaks most of these guarantees.