用代码制作一个的圆，圆心处有一个圆心角为90°的扇形，标识为G1。在圆上有1个随机的黑点，此系统拥有翻转按钮，按下此按钮，就将G1的中线移动到黑点处，并将G1变成红色.

这里提供一个Python的示例代码，使用了pygame库来实现可视化的效果：

import pygame
import random

# 初始化pygame
pygame.init()

# 定义画布的大小和圆的参数
screen_width = 600
screen_height = 600
circle_radius = 200
circle_center = (screen_width // 2, screen_height // 2)
fan_angle = 90

# 创建画布
screen = pygame.display.set_mode((screen_width, screen_height))

# 生成随机点的位置
random_point = (random.randint(0, screen_width), random.randint(0, screen_height))

# 定义圆和扇形的形状
circle_rect = pygame.Rect(circle_center[0] - circle_radius, circle_center[1] - circle_radius, circle_radius * 2, circle_radius * 2)
fan_points = [circle_center, (circle_center[0] + circle_radius, circle_center[1]), 
              pygame.mouse.get_pos(), 
              (circle_center[0], circle_center[1] + circle_radius)]

# 定义颜色
white = (255, 255, 255)
black = (0, 0, 0)
red = (255, 0, 0)

# 绘制圆和扇形
pygame.draw.circle(screen, white, circle_center, circle_radius, 1)
pygame.draw.polygon(screen, white, fan_points)
pygame.draw.circle(screen, black, random_point, 5)

# 刷新画布
pygame.display.flip()

# 循环监听事件
while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            exit(0)
        elif event.type == pygame.MOUSEBUTTONDOWN:
            # 点击鼠标左键，将中线移动到随机点并变色
            if event.button == 1:
                pygame.draw.line(screen, red, circle_center, random_point, 3)
                pygame.display.flip()
        elif event.type == pygame.KEYDOWN:
            # 按下空格键，重新生成随机点并清空中线
            if event.key == pygame.K_SPACE:
                random_point = (random.randint(0, screen_width), random.randint(0, screen_height))
                pygame.draw.circle(screen, black, random_point, 5)
                pygame.draw.polygon(screen, white, fan_points)
                pygame.display.flip()