参考：[https://gitbook.cn/gitchat/column/5b1a31bc862a01660e35955c/topic/5b1a6d8e3d723c686c30f85e]
2019-06-17

任务：绘制游戏区域（1.绘制一条线；2.绘制边界线；3.绘制网格线）

最终效果图：

图1.png

注意：每个小方格都是40×40像素，游戏区域为宽10×方格，高20×方格。
步骤开始：

1.绘制一条线：

...#与第一节内容相同
    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
        screen.fill(bg_color)
        draw_game_area(screen)
        pygame.display.flip()
def draw_game_area(screen):
    pygame.draw.line(screen, (0, 0, 0), (100, 100), (200, 200))
if __name__ =='__main__':
    main()

draw_line()函数应该在flip()之前，否则线无法显示；
pygame.draw.line()是画线，有四个参数：第一个是在screen上画线，第二个是颜色（黑色），第三与第四分别是画线起点、终点。
效果图：

图2.jpg

2.绘制边界线

最终效果如下：

图3.png

显然，需要绘制四条线，上边下边左边右边。标定四个点，我们只需要知道四个各自的坐标，即可用 pygame.draw.line()画出这四条线。
给定几个常量：
SCREEN_WIDTH, SCREEN_HEIGHT = 1200, 900 窗口的宽度与高度；
CELL_WIDTH = 40 每个方格40像素；
GAME_AREA_WIDTH, GAME_AREA_HEIGHT = CELL_WIDTH * 10, CELL_WIDTH * 20 游戏区域宽10×方格，高20×方格；
GAME_AREA_LEFT = (SCREEN_WIDTH - GAME_AREA_WIDTH) // 2 游戏区域左侧空白宽度为整个窗口宽度减去游戏区域宽度，并除以2；
GAME_AREA_TOP = SCREEN_HEIGHT - GAME_AREA_HEIGHT 游戏区域上边空白高度为整个窗口高度减去游戏区域高度；
EDGE_COLOR = (0, 0, 0) 边界线颜色黑色；
BG_COLOR = (230, 230, 230) 背景颜色自定义；
以上各常量定义在def main():之前。
由以上常量定义可得上图中点1坐标（GAME_AREA_LEFT, GAME_AREA_TOP）点2坐标（GAME_AREA_LEFT + GAME_AREA_WIDTH, GAME_AREA_TOP）点3坐标（GAME_AREA_LEFT, SCREEN_HEIGHT）点4坐标（GAME_AREA_LEFT + GAME_AREA_WIDTH, SCREEN_HEIGHT）
所以四条线就可以这样画：（定义在draw_game_area()中）

def draw_game_area(screen):
    # 上边线
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, GAME_AREA_TOP), (GAME_AREA_LEFT + GAME_AREA_WIDTH, GAME_AREA_TOP))
    # 下边线
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, SCREEN_HEIGHT), (GAME_AREA_LEFT + GAME_AREA_WIDTH, SCREEN_HEIGHT))
    # 左边线
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, GAME_AREA_TOP), (GAME_AREA_LEFT, SCREEN_HEIGHT))
    # 右边线
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT + GAME_AREA_WIDTH, GAME_AREA_TOP), (GAME_AREA_LEFT + GAME_AREA_WIDTH, SCREEN_HEIGHT))

3.绘制游戏区域网格线

图4.png

我们可以采用for循环画网格，需要在draw_game_area(screen)下一行再定义一个函数draw_grid_line(screen)
定义函数：

def draw_grid_line(screen):
    for i in range(1, 10):
        pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT + CELL_WIDTH * i, GAME_AREA_TOP), (GAME_AREA_LEFT + CELL_WIDTH * i, SCREEN_HEIGHT))
    for j in range(1, 21):
        pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, GAME_AREA_TOP + CELL_WIDTH * j), (GAME_AREA_LEFT + GAME_AREA_WIDTH, GAME_AREA_TOP + CELL_WIDTH * j))

截至目前所有代码：

import sys
import pygame
SCREEN_WIDTH = 1200
SCREEN_HEIGHT = 830
CELL_WIDTH = 40
GAME_AREA_WIDTH = CELL_WIDTH * 10
GAME_AREA_HEIGHT = CELL_WIDTH * 20
GAME_AREA_TOP = SCREEN_HEIGHT - GAME_AREA_HEIGHT
GAME_AREA_LEFT = (SCREEN_WIDTH - GAME_AREA_WIDTH) // 2
EDGE_COLOR = (0, 0, 0)
BG_COLOR = (230, 230, 230)
def main():
    pygame.init()
    screen = pygame.display.set_mode((SCREEN_WIDTH, SCREEN_HEIGHT))
    pygame.display.set_caption("俄罗斯方块")
    bg_color = BG_COLOR
    while True:
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                sys.exit()
        screen.fill(bg_color)
        draw_game_area(screen)
        draw_grid_line(screen)
        pygame.display.flip()
def draw_game_area(screen):              # (400, 30)                      (800, 30)
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, GAME_AREA_TOP), (GAME_AREA_LEFT + GAME_AREA_WIDTH, GAME_AREA_TOP))
                                        # (400, 830)                      (800, 830)
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, SCREEN_HEIGHT), (GAME_AREA_LEFT + GAME_AREA_WIDTH, SCREEN_HEIGHT))
                                        # (400, 30)                       (400, 830)
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, GAME_AREA_TOP), (GAME_AREA_LEFT, SCREEN_HEIGHT))
                                        # (800, 30)                       (800, 830)
    pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT + GAME_AREA_WIDTH, GAME_AREA_TOP), (GAME_AREA_LEFT + GAME_AREA_WIDTH, SCREEN_HEIGHT))
def draw_grid_line(screen):
    for i in range(1, 10):
        pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT + CELL_WIDTH * i, GAME_AREA_TOP), (GAME_AREA_LEFT + CELL_WIDTH * i, SCREEN_HEIGHT))
    for j in range(1, 21):
        pygame.draw.line(screen, EDGE_COLOR, (GAME_AREA_LEFT, GAME_AREA_TOP + CELL_WIDTH * j), (GAME_AREA_LEFT + GAME_AREA_WIDTH, GAME_AREA_TOP + CELL_WIDTH * j))
if __name__ == '__main__':
    main()