1  
   2  #************************************************
   3  # Rules of the game
   4  #	1. If the ant is on a black square, it turns
   5  #		right 90 and moves forward one unit
   6  #	2. If the ant is on a white square, it turns
   7  # 		left 90 and moves forward one unit
   8  #	3. When the ant leaves a square, it inverts
   9  #		colour
  10  #
  11  # SEE: http://mathworld.wolfram.com/LangtonsAnt.html
  12  #************************************************
  13  
  14  import sys, pygame
  15  from pygame.locals import *
  16  import time
  17  
  18  dirs = (
  19  		(-1, 0),
  20  		(0, 1),
  21  		(1, 0),
  22  		(0, -1)
  23  		)
  24  
  25  cellSize = 12 # size in pixels of the board (4 pixels are used to draw the grid)
  26  numCells = 64 # length of the side of the board
  27  background = 0, 0, 0 # background colour; black here
  28  foreground = 23, 23, 23 # foreground colour; the grid's colour; dark gray here
  29  textcol = 177, 177, 177 # the colour of the step display in the upper left of the screen
  30  antwalk = 44, 88, 44 # the ant's trail; greenish here
  31  antant = 222, 44, 44 # the ant's colour; red here
  32  fps = 1.0 / 40 # time between steps; 1.0 / 40 means 40 steps per second
  33  
  34  def main():
  35  	pygame.init()
  36  
  37  	size = width, height = numCells * cellSize, numCells * cellSize
  38  
  39  	pygame.display.set_caption("Langton's Ant")
  40  
  41  	screen = pygame.display.set_mode(size) # Screen is now an object representing the window in which we paint
  42  	screen.fill(background)
  43  	pygame.display.flip() # IMPORTANT: No changes are displayed until this function gets called
  44  
  45  	for i in xrange(1, numCells):
  46  		pygame.draw.line(screen, foreground, (i * cellSize, 1), (i * cellSize, numCells * cellSize), 2)
  47  		pygame.draw.line(screen, foreground, (1, i * cellSize), (numCells * cellSize, i * cellSize), 2)
  48  	pygame.display.flip() # IMPORTANT: No changes are displayed until this function gets called
  49  
  50  	font = pygame.font.Font(None, 36)
  51  
  52  	antx, anty = numCells / 2, numCells / 2
  53  	antdir = 0
  54  	board = [[False] * numCells for e in xrange(numCells)]
  55  
  56  	step = 1
  57  	pause = False
  58  	while True:
  59  		for event in pygame.event.get():
  60  				if event.type == QUIT:
  61  					return
  62  				elif event.type == KEYUP:
  63  					if event.key == 32: # If space pressed, pause or unpause
  64  						pause = not pause
  65  					elif event.key == 115:
  66  						pygame.image.save(screen, "Step%d.tga" % (step))
  67  
  68  		if pause:
  69  			time.sleep(fps)
  70  			continue
  71  
  72  		text = font.render("%d " % (step), True, textcol, background)
  73  		screen.blit(text, (10, 10))
  74  		
  75  		if board[antx][anty]:
  76  			board[antx][anty] = False # See rule 3
  77  			screen.fill(background, pygame.Rect(antx * cellSize + 1, anty * cellSize + 1, cellSize - 2, cellSize - 2))
  78  			antdir = (antdir + 1) % 4 # See rule 1
  79  		else:
  80  			board[antx][anty] = True # See rule 3
  81  			screen.fill(antwalk, pygame.Rect(antx * cellSize + 1, anty * cellSize + 1, cellSize - 2, cellSize - 2))
  82  			antdir = (antdir + 3) % 4 # See rule 2
  83  
  84  		antx = (antx + dirs[antdir][0]) % numCells
  85  		anty = (anty + dirs[antdir][1]) % numCells
  86  
  87  		# The current square (i.e. the ant) is painted a different colour
  88  		screen.fill(antant, pygame.Rect(antx * cellSize + 1, anty * cellSize + 1, cellSize -2, cellSize -2))
  89  
  90  		pygame.display.flip() # IMPORTANT: No changes are displayed until this function gets called
  91  
  92  		step += 1
  93  		time.sleep(fps)
  94  
  95  if __name__ == "__main__":
  96  	main()