def draw_tree(length, width=9):
    color = 'brown'
    if length < 1:
        return
    elif length < 3:
        color = 'green'

    if width < 1:
        width = 1

    turtle.color(color)
    turtle.width(width)
    turtle.forward(length)
    turtle.left(30)
    draw_tree(length / FACTOR, width - 1)
    turtle.right(60)
    draw_tree(length / FACTOR, width - 1)
    turtle.left(30)
    turtle.color(color)
    turtle.width(width)
    turtle.backward(length) 

def gear(count, width, height):

    angle = 90-(180/count)

    for _ in range(count):
        turtle.forward(width)
        turtle.left(angle)
        turtle.forward(height)
        turtle.right(90)
        turtle.forward(width)
        turtle.right(90)
        turtle.forward(height)
        turtle.left(angle)

# --- main ---

# clear everything 

def gear(count, width, height):

    angle = 90-(180/count)

    for _ in range(count):
        turtle.forward(width)
        turtle.left(angle)
        turtle.forward(height)
        turtle.right(90)
        turtle.forward(width)
        turtle.right(90)
        turtle.forward(height)
        turtle.left(angle)

# --- main ---

# clear everything 

def draw_pattern_rectangle(x, y, width, height, count, radius, color='red'):
    rotation = 360 / count

    turtle.goto(x, y)
    
    for _ in range(count):
        # move from center to circle
        turtle.pu()
        #turtle.color('black')
        turtle.forward(radius)
        turtle.right(90+rotation/2)
        
        draw_rectangle(width, height, color)

        # move from circle to center
        turtle.pu()
        #turtle.color('black')
        turtle.left(90+rotation/2)
        turtle.backward(radius)

        # rotate in circle
        turtle.right(rotation) 

def draw_pattern_circle(x, y, r, count, radius, color='red'):
    rotation = 360 / count

    turtle.goto(x, y)

    for _ in range(count):
        # move from center to circle
        #turtle.pu()
        turtle.color('black')
        turtle.forward(radius)
        turtle.right(90)

        draw_circle(r, color)

        # move from circle to center
        #turtle.pu()
        turtle.color('black')
        turtle.left(90)
        turtle.backward(radius)

        # rotate in circle
        turtle.right(rotation) 

def item(lenght, level, color):
    if level <= 0:
        return
    
    for _ in range(5):    # 5
        turtle.color(colors[color])
        turtle.forward(lenght)
        
        item(lenght/4, level-1, color+1)
        
        turtle.penup() # there is no need to draw again the same line  (and it can use differnt color)
        turtle.backward(lenght)
        turtle.pendown()
        
        turtle.right(360/8) # 8
    
    turtle.right(360/8 * 3) # 3 = 8 - 5 

def move(distance):
	turtle.penup()
	turtle.forward(distance)
	turtle.pendown() 

def createHand(name, length):
	turtle.reset()
	move(-length * 0.01)
	turtle.begin_poly()
	turtle.forward(length * 1.01)
	turtle.end_poly()
	hand = turtle.get_poly()
	turtle.register_shape(name, hand) 

def createClock(radius):
	turtle.reset()
	turtle.pensize(7)
	for i in range(60):
		move(radius)
		if i % 5 == 0:
			turtle.forward(20)
			move(-radius-20)
		else:
			turtle.dot(5)
			move(-radius)
		turtle.right(6) 

def startTick(second_hand, minute_hand, hour_hand, printer):
	today = datetime.datetime.today()
	second = today.second + today.microsecond * 1e-6
	minute = today.minute + second / 60.
	hour = (today.hour + minute / 60) % 12
	# 设置朝向
	second_hand.setheading(6 * second)
	minute_hand.setheading(6 * minute)
	hour_hand.setheading(12 * hour)
	turtle.tracer(False)
	printer.forward(65)
	printer.write(getWeekday(today), align='center', font=("Courier", 14, "bold"))
	printer.forward(120)
	printer.write('12', align='center', font=("Courier", 14, "bold"))
	printer.back(250)
	printer.write(getDate(today), align='center', font=("Courier", 14, "bold"))
	printer.back(145)
	printer.write('6', align='center', font=("Courier", 14, "bold"))
	printer.home()
	printer.right(92.5)
	printer.forward(200)
	printer.write('3', align='center', font=("Courier", 14, "bold"))
	printer.left(2.5)
	printer.back(400)
	printer.write('9', align='center', font=("Courier", 14, "bold"))
	printer.home()
	turtle.tracer(True)
	# 100ms调用一次
	turtle.ontimer(lambda: startTick(second_hand, minute_hand, hour_hand, printer), 100) 

def draw_koch(size, depth):
    if depth > 0:
        for angle in ANGLES:
            draw_koch(size / 3, depth - 1)
            turtle.left(angle)
    else:
        turtle.forward(size) 

def draw_snowflake(size):
    """ Draw a picture of a snowflake """
    turtle.penup()
    turtle.forward(10 * size)
    turtle.left(45)
    turtle.pendown()
    turtle.color(generate_random_colour())

    # draw branch 8 times to make a snowflake
    for _ in range(8):
        draw_branch(size)
        turtle.forward(size)
        turtle.left(45)

    turtle.penup() 

def draw_branch(size):
    """ Draw an individual branch on a snowflake """
    side_branch_size = size / 3
    for _ in range(3):
        for i in range(3):
            turtle.forward(side_branch_size)
            turtle.backward(side_branch_size)
            turtle.right(45)
        turtle.left(90)
        turtle.backward(side_branch_size)
        turtle.left(45)
    turtle.right(90) 

def draw_square(size):
    """ Function to draw a square """
    turtle.forward(size)
    turtle.right(90)
    turtle.forward(size)
    turtle.right(90)
    turtle.forward(size)
    turtle.right(90)
    turtle.forward(size) 

def hexagon():
    for _ in range(6):
        turtle.forward(50)
        turtle.left(60) 

def square(x, y, size, name):
    """Draw square at `(x, y)` with side length `size` and fill color `name`.

    The square is oriented so the bottom left corner is at (x, y).

    """
    import turtle
    turtle.up()
    turtle.goto(x, y)
    turtle.down()
    turtle.color(name)
    turtle.begin_fill()

    for count in range(4):
        turtle.forward(size)
        turtle.left(90)

    turtle.end_fill() 

def draw_rectangle(size):
    for _ in range(4):
        turtle.forward(size)
        turtle.left(90)

# --- main ---

# clear everything 

def draw_rectangle(size):
    for _ in range(4):
        turtle.forward(size)
        turtle.left(90)

# --- main ---

# clear everything 

def draw_rectangle(size):
    for _ in range(4):
        turtle.forward(size)
        turtle.left(90)

# --- main ---

# clear everything 

def draw_rectangle(size):
    for _ in range(4):
        turtle.forward(size)
        turtle.left(90)

# --- main ---

# clear everything 

def draw_rectangle(size):
    for _ in range(4):
        turtle.forward(size)
        turtle.left(90)

# --- main ---

# clear everything 

def move():
    if running:
        t.forward(15)
        angle = random.randint(-9, 9) * 10 
        t.left(angle)
        t.ontimer(move, 25) # 25ms 

def forward():
    turtle.setheading(90)
    turtle.forward(100) 

def backward():
    turtle.setheading(270)
    turtle.forward(100) 

def left():
    turtle.setheading(180)
    turtle.forward(100) 

def right():
    turtle.setheading(0)
    turtle.forward(100) 

def draw():
    turtle.forward(50)
    turtle.left(30)
    turtle.forward(50)
    turtle.left(30)

# access to tkinter - tk & root
# instead of standard
# import tkinter as tk
# root = tk.Tk() 

def dragon(level=1, remove_plus_minus=False, width=5):

    a = 'FX'

    rule = {
        'X': 'X+YF+',
        'Y': '-FX-Y',
        '-': '-',
        '+': '+',
        'F': 'F',
    }

    for _ in range(level):
        a = ''.join(rule[x] for x in a)

    print('len:', len(a))

    a = a.replace('X', '').replace('Y','')
    print('len without X, Y:', len(a))
    
    if remove_plus_minus:
        a = a.replace('+-', '').replace('-+', '')
        print('len without -+, +-:', len(a))
            
    for x in a:
        if x == 'F':
            turtle.forward(width)
        elif x == '+':        
            turtle.right(90)
            turtle.color('red')
        elif x == '-':
            turtle.left(90)
            turtle.color('green')

    print('OK')
    
# --- main ---

# clear everything 

def flower(size):
    for _ in range(36):
        turtle.forward(size)
        turtle.left(110)

# --- main ---

# clear everything 

def flower(size):
    for _ in range(36):
        turtle.forward(size)
        turtle.left(110)

# --- main ---

# clear everything