前言
在之前Python学习笔记中，学习过python第三方库pygame的三大基本机制和最小游戏设计框架。我们对国民偶像蔡徐坤进行了动态展示。之后，闲来无事实现了小时候玩过的小游戏贪食蛇。
具体参考笔记一：python第三方库pygame学习笔记(一)
游戏机制
玩过贪食蛇的朋友对贪食蛇的游戏机制并不会陌生。大致如下：
1、控制初始生成的小蛇进行移动进而吃到随机生成的食物，用于增加自己的长度
2、当小蛇撞墙或头碰到自己的身体则游戏结束
源码参考：python 贪吃蛇小游戏代码
本文中新加的小彩蛋：
1、当小蛇吃到食物达到指定数量的时候，屏幕上会额外刷新一个奖励即生命
2、小蛇的额外生命能用于抵消传统游戏机制2的影响：触墙生命-1，头碰到自己身体则生命清零
3、小蛇会随着吃到的食物数量进而增加自己的移动速度
设计思想
在学习了自顶向下设计和自底向上实现的编程思想后，试着将贪食蛇的代码实现进行模块化编写。大致可以从如下流程图出发
程序代码
import random
import pygame
import sys
from pygame.locals import *
Window_Width = 800
Window_Height = 500
Cell_Size = 20 # Width and height of the cells
# Ensuring that the cells fit perfectly in the window. eg if cell size was
# 10 and window width or windowheight were 15 only 1.5 cells would
# fit.
assert Window_Width % Cell_Size == 0, "Window width must be a multiple of cell size."
# Ensuring that only whole integer number of cells fit perfectly in the window.
assert Window_Height % Cell_Size == 0, "Window height must be a multiple of cell size."
Cell_W = int(Window_Width / Cell_Size) # Cell Width
Cell_H = int(Window_Height / Cell_Size) # Cellc Height
White = (255, 255, 255)
Black = (0, 0, 0)
Red = (255, 0, 0) # Defining element colors for the program.
Green = (0, 255, 0)
DARKGreen = (0, 155, 0)
DARKGRAY = (40, 40, 40)
YELLOW = (255, 255, 0)
Red_DARK = (150, 0, 0)
BLUE = (0, 0, 255)
BLUE_DARK = (0, 0, 150)
BGCOLOR = Black # Background color
HEAD = 0 # Syntactic sugar: index of the snake's head
#绘制分数和声明
def drawLife(life):
lifeSurf=BASICFONT.render('Life: %s' % (life), True, Red)
lifeRect=lifeSurf.get_rect()
lifeRect.topleft=(Window_Width-240,10)
DISPLAYSURF.blit(lifeSurf,lifeRect)
def drawScore(score):
scoreSurf = BASICFONT.render('Score: %s' % (score), True, White)
scoreRect = scoreSurf.get_rect()
scoreRect.topleft = (Window_Width - 120, 10)
DISPLAYSURF.blit(scoreSurf, scoreRect)
def drawWorm(wormCoords,life,getLife):
for coord in wormCoords:
x = coord['x'] * Cell_Size
y = coord['y'] * Cell_Size
wormSegmentRect = pygame.Rect(x, y, Cell_Size, Cell_Size)
pygame.draw.rect(DISPLAYSURF, DARKGreen, wormSegmentRect)
wormInnerSegmentRect = pygame.Rect(
x + 4, y + 4, Cell_Size - 8, Cell_Size - 8)
if life>0:
pygame.draw.rect(DISPLAYSURF, (255,255-life*20,life*20), wormInnerSegmentRect)
else:
pygame.draw.rect(DISPLAYSURF, Green, wormInnerSegmentRect)
# 绘制食物
def drawApple(coord):
x = coord['x'] * Cell_Size
y = coord['y'] * Cell_Size
appleRect = pygame.Rect(x, y, Cell_Size, Cell_Size)
pygame.draw.rect(DISPLAYSURF, Red, appleRect)
# 绘制奖励
def drawPrice(coord):
x = coord['x'] * Cell_Size
y = coord['y'] * Cell_Size
priceRect = pygame.Rect(x, y, Cell_Size, Cell_Size)
pygame.draw.ellipse(DISPLAYSURF, YELLOW, priceRect)
def drawGrid():
for x in range(0, Window_Width, Cell_Size): # draw vertical lines
pygame.draw.line(DISPLAYSURF, DARKGRAY, (x, 0), (x, Window_Height))
for y in range(0, Window_Height, Cell_Size): # draw horizontal lines
pygame.draw.line(DISPLAYSURF, DARKGRAY, (0, y), (Window_Width, y))
def enlargeBody(direction, wormCoords):
# move the worm by adding a segment in the direction it is moving
if direction == 'up':
newHead = {'x': wormCoords[HEAD]['x'],
'y': wormCoords[HEAD]['y'] - 1}
elif direction == 'down':
newHead = {'x': wormCoords[HEAD]['x'],
'y': wormCoords[HEAD]['y'] + 1}
elif direction == 'left':
newHead = {'x': wormCoords[HEAD][
'x'] - 1, 'y': wormCoords[HEAD]['y']}
elif direction == 'right':
newHead = {'x': wormCoords[HEAD][
'x'] + 1, 'y': wormCoords[HEAD]['y']}
return newHead
def drawPressKeyMsg():
pressKeySurf = BASICFONT.render('Press a key to play.', True, White)
pressKeyRect = pressKeySurf.get_rect()
pressKeyRect.topleft = (Window_Width - 200, Window_Height - 30)
DISPLAYSURF.blit(pressKeySurf, pressKeyRect)
def checkForKeyPress():
if len(pygame.event.get(QUIT)) > 0:
terminate()
keyUpEvents = pygame.event.get(KEYUP)
if len(keyUpEvents) == 0:
return False
elif keyUpEvents[0].key == K_ESCAPE:
terminate()
else:
return keyUpEvents[0].key
def showStartScreen():
titleFont = pygame.font.Font('freesansbold.ttf', 100)
titleSurf1 = titleFont.render('Snake!', True, White, DARKGreen)
degrees1 = 0
degrees2 = 0
while True:
DISPLAYSURF.fill(BGCOLOR)
rotatedSurf1 = pygame.transform.rotate(titleSurf1, degrees1)
rotatedRect1 = rotatedSurf1.get_rect()
rotatedRect1.center = (Window_Width / 2, Window_Height / 2)
DISPLAYSURF.blit(rotatedSurf1, rotatedRect1)
drawPressKeyMsg()
if checkForKeyPress():
pygame.event.get() # clear event queue
return
pygame.display.update()
SnakespeedCLOCK.tick(17)
degrees1 += 3 # rotate by 3 degrees each frame
degrees2 += 7 # rotate by 7 degrees each frame
def terminate():
pygame.quit()
sys.exit()
def getRandomLocation():
return {'x': random.randint(0, Cell_W - 1), 'y': random.randint(0, Cell_H - 1)}
def showGameOverScreen():
gameOverFont = pygame.font.Font('freesansbold.ttf', 100)
gameSurf = gameOverFont.render('Game', True, White)
overSurf = gameOverFont.render('Over', True, White)
gameRect = gameSurf.get_rect()
overRect = overSurf.get_rect()
gameRect.midtop = (Window_Width / 2, 10)
overRect.midtop = (Window_Width / 2, gameRect.height + 10 + 25)
DISPLAYSURF.blit(gameSurf, gameRect)
DISPLAYSURF.blit(overSurf, overRect)
drawPressKeyMsg()
pygame.display.update()
pygame.event.get()
while True:
if checkForKeyPress():
pygame.event.get() # clear event queue
return
def main():
global SnakespeedCLOCK, DISPLAYSURF, BASICFONT
pygame.init()
SnakespeedCLOCK = pygame.time.Clock()
DISPLAYSURF = pygame.display.set_mode((Window_Width, Window_Height))
BASICFONT = pygame.font.Font('freesansbold.ttf', 18)
pygame.display.set_caption('Snake')
showStartScreen()
while True:
runGame()
showGameOverScreen()
def runGame():
# Set a random start point.
checkForKeyPress()
cnt = 0
life = 0 # 初始分数和奖励为0
getLife=0
Snakespeed=10
startx = random.randint(20, Cell_W - 8)
starty = random.randint(6, Cell_H - 6)
wormCoords = [{'x': startx, 'y': starty},
{'x': startx - 1, 'y': starty},
{'x': startx - 2, 'y': starty}]
initialDir = ['up', 'down', 'right']
statusDir = random.randint(0, 2)
direction = initialDir[statusDir]
# Start the apple in a random place.
apple = getRandomLocation()
priceInitial = {'x':Window_Width,'y':Window_Height}
price=priceInitial
while True: # main game loop
for event in pygame.event.get(): # event handling loop
if event.type == QUIT:
terminate()
elif event.type == KEYDOWN:
if (event.key == K_LEFT or event.key == K_a) and direction != 'right':
direction = 'left'
elif (event.key == K_RIGHT or event.key == K_d) and direction != 'left':
direction = 'right'
elif (event.key == K_UP or event.key == K_w) and direction != 'down':
direction = 'up'
elif (event.key == K_DOWN or event.key == K_s) and direction != 'up':
direction = 'down'
elif event.key == K_ESCAPE:
terminate()
# check if the Snake has hit itself or the edge
if (wormCoords[HEAD]['x'] == -1 or wormCoords[HEAD]['x'] == Cell_W or wormCoords[HEAD]['y'] == -1 or \
wormCoords[HEAD]['y'] == Cell_H) and life != 0:
if life > 0:
if wormCoords[HEAD]['x'] == -1:
wormCoords[HEAD]['x'] = Cell_W - 1
life -= 1
elif wormCoords[HEAD]['x'] == Cell_W:
wormCoords[HEAD]['x'] = 0
life -= 1
elif wormCoords[HEAD]['y'] == -1:
wormCoords[HEAD]['y'] = Cell_H - 1
life -= 1
elif wormCoords[HEAD]['y'] == Cell_H:
wormCoords[HEAD]['y'] = 0
life -= 1
elif (wormCoords[HEAD]['x'] == -1 or wormCoords[HEAD]['x'] == Cell_W or wormCoords[HEAD]['y'] == -1 or \
wormCoords[HEAD]['y'] == Cell_H) and life == 0:
return True
for wormBody in wormCoords[1:]:
if wormBody['x'] == wormCoords[HEAD]['x'] and wormBody['y'] == wormCoords[HEAD]['y']:
if life == 0:
return True # game over
else:
life=0
# check if Snake has eaten an apple or price
if wormCoords[HEAD]['x'] == apple['x'] and wormCoords[HEAD]['y'] == apple['y']:
# don't remove worm's tail segment
apple = getRandomLocation() # set a new apple somewhere
cnt += 1
newHead = enlargeBody(direction, wormCoords)
wormCoords.insert(0, newHead)
#游戏加速
Snakespeed+=cnt//5
if cnt in [1,3,5,7,9]:
price = getRandomLocation()
getLife+=1
if wormCoords[HEAD]['x'] == price['x'] and wormCoords[HEAD]['y'] == price['y']:
getLife-=1
life += 1
price = priceInitial
else:
del wormCoords[-1] # remove worm's tail segment
# 奖励机制
newHead = enlargeBody(direction, wormCoords)
wormCoords.insert(0, newHead)
DISPLAYSURF.fill(BGCOLOR)
drawGrid()
drawWorm(wormCoords,life,getLife)
drawApple(apple)
drawPrice(price)
drawScore(cnt)
drawLife(life)
pygame.display.update()
SnakespeedCLOCK.tick(Snakespeed)
if __name__ == '__main__':
try:
main()
except SystemExit:
pass
后记
感觉贪食蛇如果彩蛋加的比较多的话，可玩性也不是没有。比如当我们碰到自己身体的时候，不单单是清空生命，而是咬掉这一段。。积分过了多少，出现反键状态，得分double。想想都好玩。如果后续实现了，会继续贴出来的。毕竟我是个菜鸡。