How to score a player in pygame

[nnekymoe]

I'm new to pygame and currently I'm working on creating a memory game where the computer displays boxes at random positions for like a second and then the user has to click on where he/she thinks those boxes are. It's kind of like this: Click Here

However right now I'm having a few problems.
I'm not really sure how to make the computer display the boxes with like a letter or symbol e.g. 'T' or '%'. (I've already made the grid).
Also does anyone know how to add increase the players score when they get the right box?

Any help would be appreciated. Thank you.

import pygame
size=[500,500]
pygame.init()
screen=pygame.display.set_mode(size)

# Colours
LIME = (0,255,0) 
RED = (255, 0, 0)
BLACK = (0,0,0)
PINK = (255,102,178)
SALMON = (255,192,203)
WHITE = (255,255,255)
LIGHT_PINK = (255, 181, 197)
SKY_BLUE = (176, 226, 255)
screen.fill(BLACK)

score = 0

# Width and Height of game box
width=50
height=50

# Margin between each cell
margin = 5

# Create a 2 dimensional array. A two dimesional
# array is simply a list of lists.
grid=[]
for row in range(20):
    # Add an empty array that will hold each cell
    # in this row
    grid.append([])
    for column in range(20):
        grid[row].append(0) # Append a cell

# Set row 1, cell 5 to one. (Remember rows and
# column numbers start at zero.)
grid[1][5] = 1  

# Set title of screen
pygame.display.set_caption("Spatial Recall")

#Loop until the user clicks the close button.
done=False

# Used to manage how fast the screen updates
clock=pygame.time.Clock()

# -------- Main Program Loop -----------
while done==False:
    for event in pygame.event.get(): # User did something
        if event.type == pygame.QUIT: # If user clicked close
            done=True # Flag that we are done so we exit this loop
        if event.type == pygame.MOUSEBUTTONDOWN:
            # User clicks the mouse. Get the position
            pos = pygame.mouse.get_pos()
            # Change the x/y screen coordinates to grid coordinates
            column=pos[0] // (width+margin)
            row=pos[1] // (height+margin)
            # Sete t hat location to zero
            grid[row][column]=1
            print("Click ",pos,"Grid coordinates: ",row,column)


    # Draw the grid
    for row in range(10):
        for column in range(10):
            color = LIGHT_PINK
            if grid[row][column] == 1:
                color = RED
            pygame.draw.rect(screen,color,[(margin+width)*column+margin,(margin+height)*row+margin,width,height])

    # Limit to 20 frames per second
    clock.tick(20)

    # Go ahead and update the screen with what we've drawn.
    pygame.display.flip()

screen.blit(screen, rect)     

def play_again():
    # indicates that the player can replay
    mess = police.render('click to replay',1,gray, orange)
    pygame.display.update(scr.blit(mess,mess.get_rect(center=scrrect.center)))
    while True:
        ev = pygame.event.wait()
        if ev.type   == pygame.MOUSEBUTTONDOWN: return True
        elif ev.type == pygame.QUIT: return False

        def draw_hidden():
            # draws and displays the cards faces hidden © es
            scr.fill(orange)
            for y in range(0,scrrect.h,cellsize):
                for x in range(0,scrrect.w,cellsize):
                    scr.fill(noir,(x+1,y+1,cellsize-2,cellsize-2))
                    pygame.display.flip()

pygame.quit ()