LEVELS = {
    'easy': 2,
    'medium': 3,
    'hard': 4,
}

GRID_SIZE = 11 # 11 * 11 grid

CORNERS = (
    (0, 0),
    (0, GRID_SIZE - 1),
    (GRID_SIZE - 1, 0),
    (GRID_SIZE - 1, GRID_SIZE - 1)
)