Building and visualizing Sudoku Game Using Pygame

Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids that compose the grid contain all of the digits from 1 to 9. 

We will be building the Sudoku Game in python using pygame library and automate the game using backtracking algorithm. 

Features Implemented :

• Game Interface to Play
• Auto solving
• Visualization of auto solving i.e., Backtracking Algorithm visualization
• Options: Reset, Clear game

Prerequisite :

• Pygame Library must be preinstalled
• Knowledge on Backtracking Algorithm

Implementation Steps :

1. Fill the pygame window with Sudoku Board i.e., Construct a 9×9 grid. 
2. Fill the board with default numbers. 
3. Assign a specific key for each operations and listen it. 
4. Integrate the backtracking algorithm into it. 
5. Use set of colors to visualize auto solving.

Instruction:

• Press ‘Enter’ To Auto Solve and Visualize.
• To play the game manually,
  Place the cursor in any cell you want and enter the number.
• At any point, press enter to solve automatically.

Below is the Implementation :

Python3

# import pygame library
import pygame

# initialise the pygame font
pygame.font.init()

# Total window
screen = pygame.display.set_mode((500, 600))

# Title and Icon
pygame.display.set_caption("SUDOKU SOLVER USING BACKTRACKING")
img = pygame.image.load('icon.png')
pygame.display.set_icon(img)

x = 0
y = 0
dif = 500 / 9
val = 0
# Default Sudoku Board.
grid =[
        [7, 8, 0, 4, 0, 0, 1, 2, 0],
        [6, 0, 0, 0, 7, 5, 0, 0, 9],
        [0, 0, 0, 6, 0, 1, 0, 7, 8],
        [0, 0, 7, 0, 4, 0, 2, 6, 0],
        [0, 0, 1, 0, 5, 0, 9, 3, 0],
        [9, 0, 4, 0, 6, 0, 0, 0, 5],
        [0, 7, 0, 3, 0, 0, 0, 1, 2],
        [1, 2, 0, 0, 0, 7, 4, 0, 0],
        [0, 4, 9, 2, 0, 6, 0, 0, 7]
    ]

# Load test fonts for future use
font1 = pygame.font.SysFont("comicsans", 40)
font2 = pygame.font.SysFont("comicsans", 20)
def get_cord(pos):
    global x
    x = pos[0]//dif
    global y
    y = pos[1]//dif

# Highlight the cell selected
def draw_box():
    for i in range(2):
        pygame.draw.line(screen, (255, 0, 0), (x * dif-3, (y + i)*dif), (x * dif + dif + 3, (y + i)*dif), 7)
        pygame.draw.line(screen, (255, 0, 0), ( (x + i)* dif, y * dif ), ((x + i) * dif, y * dif + dif), 7)

# Function to draw required lines for making Sudoku grid
def draw():
    # Draw the lines

    for i in range (9):
        for j in range (9):
            if grid[i][j]!= 0:

                # Fill blue color in already numbered grid
                pygame.draw.rect(screen, (0, 153, 153), (i * dif, j * dif, dif + 1, dif + 1))

                # Fill grid with default numbers specified
                text1 = font1.render(str(grid[i][j]), 1, (0, 0, 0))
                screen.blit(text1, (i * dif + 15, j * dif + 15))
    # Draw lines horizontally and verticallyto form grid
    for i in range(10):
        if i % 3 == 0 :
            thick = 7
        else:
            thick = 1
        pygame.draw.line(screen, (0, 0, 0), (0, i * dif), (500, i * dif), thick)
        pygame.draw.line(screen, (0, 0, 0), (i * dif, 0), (i * dif, 500), thick)

# Fill value entered in cell
def draw_val(val):
    text1 = font1.render(str(val), 1, (0, 0, 0))
    screen.blit(text1, (x * dif + 15, y * dif + 15))

# Raise error when wrong value entered
def raise_error1():
    text1 = font1.render("WRONG !!!", 1, (0, 0, 0))
    screen.blit(text1, (20, 570))
def raise_error2():
    text1 = font1.render("Wrong !!! Not a valid Key", 1, (0, 0, 0))
    screen.blit(text1, (20, 570))

# Check if the value entered in board is valid
def valid(m, i, j, val):
    for it in range(9):
        if m[i][it]== val:
            return False
        if m[it][j]== val:
            return False
    it = i//3
    jt = j//3
    for i in range(it * 3, it * 3 + 3):
        for j in range (jt * 3, jt * 3 + 3):
            if m[i][j]== val:
                return False
    return True

# Solves the sudoku board using Backtracking Algorithm
def solve(grid, i, j):

    while grid[i][j]!= 0:
        if i<8:
            i+= 1
        elif i == 8 and j<8:
            i = 0
            j+= 1
        elif i == 8 and j == 8:
            return True
    pygame.event.pump()
    for it in range(1, 10):
        if valid(grid, i, j, it)== True:
            grid[i][j]= it
            global x, y
            x = i
            y = j
            # white color background\
            screen.fill((255, 255, 255))
            draw()
            draw_box()
            pygame.display.update()
            pygame.time.delay(20)
            if solve(grid, i, j)== 1:
                return True
            else:
                grid[i][j]= 0
            # white color background\
            screen.fill((255, 255, 255))

            draw()
            draw_box()
            pygame.display.update()
            pygame.time.delay(50)
    return False

# Display instruction for the game
def instruction():
    text1 = font2.render("PRESS D TO RESET TO DEFAULT / R TO EMPTY", 1, (0, 0, 0))
    text2 = font2.render("ENTER VALUES AND PRESS ENTER TO VISUALIZE", 1, (0, 0, 0))
    screen.blit(text1, (20, 520))
    screen.blit(text2, (20, 540))

# Display options when solved
def result():
    text1 = font1.render("FINISHED PRESS R or D", 1, (0, 0, 0))
    screen.blit(text1, (20, 570))
run = True
flag1 = 0
flag2 = 0
rs = 0
error = 0
# The loop thats keep the window running
while run:

    # White color background
    screen.fill((255, 255, 255))
    # Loop through the events stored in event.get()
    for event in pygame.event.get():
        # Quit the game window
        if event.type == pygame.QUIT:
            run = False
        # Get the mouse position to insert number
        if event.type == pygame.MOUSEBUTTONDOWN:
            flag1 = 1
            pos = pygame.mouse.get_pos()
            get_cord(pos)
        # Get the number to be inserted if key pressed
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                x-= 1
                flag1 = 1
            if event.key == pygame.K_RIGHT:
                x+= 1
                flag1 = 1
            if event.key == pygame.K_UP:
                y-= 1
                flag1 = 1
            if event.key == pygame.K_DOWN:
                y+= 1
                flag1 = 1
            if event.key == pygame.K_1:
                val = 1
            if event.key == pygame.K_2:
                val = 2
            if event.key == pygame.K_3:
                val = 3
            if event.key == pygame.K_4:
                val = 4
            if event.key == pygame.K_5:
                val = 5
            if event.key == pygame.K_6:
                val = 6
            if event.key == pygame.K_7:
                val = 7
            if event.key == pygame.K_8:
                val = 8
            if event.key == pygame.K_9:
                val = 9
            if event.key == pygame.K_RETURN:
                flag2 = 1
            # If R pressed clear the sudoku board
            if event.key == pygame.K_r:
                rs = 0
                error = 0
                flag2 = 0
                grid =[
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0],
                [0, 0, 0, 0, 0, 0, 0, 0, 0]
                ]
            # If D is pressed reset the board to default
            if event.key == pygame.K_d:
                rs = 0
                error = 0
                flag2 = 0
                grid =[
                    [7, 8, 0, 4, 0, 0, 1, 2, 0],
                    [6, 0, 0, 0, 7, 5, 0, 0, 9],
                    [0, 0, 0, 6, 0, 1, 0, 7, 8],
                    [0, 0, 7, 0, 4, 0, 2, 6, 0],
                    [0, 0, 1, 0, 5, 0, 9, 3, 0],
                    [9, 0, 4, 0, 6, 0, 0, 0, 5],
                    [0, 7, 0, 3, 0, 0, 0, 1, 2],
                    [1, 2, 0, 0, 0, 7, 4, 0, 0],
                    [0, 4, 9, 2, 0, 6, 0, 0, 7]
                ]
    if flag2 == 1:
        if solve(grid, 0, 0)== False:
            error = 1
        else:
            rs = 1
        flag2 = 0
    if val != 0:
        draw_val(val)
        # print(x)
        # print(y)
        if valid(grid, int(x), int(y), val)== True:
            grid[int(x)][int(y)]= val
            flag1 = 0
        else:
            grid[int(x)][int(y)]= 0
            raise_error2()
        val = 0

    if error == 1:
        raise_error1()
    if rs == 1:
        result()
    draw()
    if flag1 == 1:
        draw_box()
    instruction()

    # Update window
    pygame.display.update()

# Quit pygame window
pygame.quit()

Output: