stack = []
enum Direction { LEFT, RIGHT}

def detect(distance): #return whether odometer is reading less than 30
    return True #if the US reading is less than the distance (bug antenna)

def find_closest_wall(): #calculates what the nearest wall or river is, in the direction perpendicaular to the direction of travel
    return LEFT




def avoid():
    avoid_direction = find_closest_wall() == Direction.LEFT ? Direction.RIGHT : Direction.RIGHT #opposite of the closest_wall direction

    rotate(90, avoid_direction) # blocking
    stack.add(avoid_direction)

    while stack: #is not empty
        if detect(30):
            rotate(90, avoid_direction) # blocking
            stack.push(avoid_direction) #push rotation onto stack to undo eventually
        else:
            straight(30, "forward")
            rotate(90, stack.pop())


if obstacle:
    avoid()


stack = [right]
stack = [right, right]
stack = [right]
stack = []
stack = [right]
stack = []
stack = []
stack = []
stack = []