我想在pygame中用python代码使太阳系只有两个性质：地球绕太阳转，月球绕地球连续运行。这是我的代码：import sys, random, math

import pygame

from pygame.locals import *

pygame.init()

black = 0, 0, 0

white = 255, 255, 255

grey = 125, 125, 125

red = 255, 0, 0

blue = 0, 0, 255

width = 500

height = 500

screen = pygame.display.set_mode((width,height))

screen.fill(white)

clock = pygame.time.Clock()

font = pygame.font.Font(None, 15)

def rotate2D(x,y,angle):

angle = 0.0174532925*angle

x_r = x*math.cos(angle) - y*math.sin(angle)

y_r = x*math.sin(angle) + y*math.cos(angle)

return (x_r, y_r)

def translate2D(x,y,tx,ty):

x_t = x+tx

y_t = y+ty

return (x_t, y_t)

def show_FPS():

text = font.render('day = ' + '{:.2f}'.format(day) + ', ' + str(int(clock.get_fps())) + ' FPS', True, black, white)

textRect = text.get_rect()

textRect.bottomright = screen.get_rect().bottomright

screen.blit(text, textRect)

sun_radius = 70

earth_radius = 15

ex = 0

ey = 0

moon_radius = 10

mx = 0

my = 0

sun2earth_dis = 200

moon2earth_dis = 90

sun2earth_orbit = 0

moon2earth_orbit = 0

day = 0

flag = 1

while flag:

clock.tick(60)

for event in pygame.event.get():

if event.type == pygame.QUIT:

flag = 0

if event.type == pygame.KEYUP and event.key == pygame.K_ESCAPE:

flag = 0

screen.fill(white)

day = day+0.2

sun2earth_orbit = -(day*360.0)/365

moon2earth_orbit = -(day*360.0)/27

ex_, ey_ = translate2D(ex, ey, sun2earth_dis, 0)

ex_, ey_ = translate2D(ex_, ey_, width/2, height/2)

mx_, my_ = translate2D(mx, my, moon2earth_dis, 0)

mx_, my_ = rotate2D(mx_, my_, moon2earth_orbit)

mx_, my_ = translate2D(mx_, my_, width/2, height/2)

pygame.draw.circle(screen, red, (int(width/2), int(height/2)), sun_radius)

pygame.draw.circle(screen, blue, (int(ex_), int(ey_)), earth_radius)

pygame.draw.circle(screen, black, (int(mx_), int(my_)), moon_radius)

show_FPS()

pygame.display.flip()

pygame.quit()

在这个密码里，地球绕着太阳转。看起来不错。现在我想让月亮绕着地球转，它一直绕着地球和太阳转。我设定地球在365天内移动太阳一个完整的圆，在月球上它将在27天内绕地球运行。在

关于细节(这是我想发展的最初想法)：

轨道速度：

地球绕太阳一周365天，

月亮绕太阳转了27天

纺纱速度：

太阳在30天内转一圈，

地球在一天内转一圈，

月亮总是面向地球

我已经做到了。但是月亮是如何绕太阳转的这个想法我还不清楚。在