pygame_mouse_squares.py

import pygame
import sys #will use the exit function
from random import randint

#Loads all the main pygame modules and initializes them
pygame.init()

clock = pygame.time.Clock()

screen_width=640
screen_height=480

#Sidelength of all of our squares
sideLength = 40

rectDict = dict()

for x in range(0, screen_width, sideLength):
    for y in range (0, screen_height, sideLength):
        rectDict[(x,y)] = {'rect':pygame.Rect(x, y, sideLength, sideLength),
                           'color':(255,0,0)}

#Create a new Surface with the dimensions listed above
screen=pygame.display.set_mode((screen_width, screen_height))

#Loop forever:
while True:
    
    clock.tick(60)
    
    #The following makes the window close when clicking the "X" or exit button
    #Without this, the window will not close, and will need to be killed
    #with the task manager
    for event in pygame.event.get():
        if event.type == pygame.QUIT: sys.exit()
        elif event.type == pygame.MOUSEBUTTONDOWN:
            clickLocation = pygame.mouse.get_pos()
            #print(clickLocation)
            nearestX = clickLocation[0] - (clickLocation[0] % sideLength)
            nearestY = clickLocation[1] - (clickLocation[1] % sideLength)
            clickedRect = rectDict[(nearestX, nearestY)]
            clickedRect['color'] = (randint(0,255),
                                    randint(0,255),
                                    randint(0,255))
            
            
            
    
    for r in rectDict:
        pygame.draw.rect(screen, rectDict[r]['color'], rectDict[r]['rect'])
    
    pygame.display.flip()