A Grid of Cells

Lesson 19 of 40 in Coddy's Make Games with Pygame course.

Snake moves on a grid. The window is 24 columns by 18 rows of cells, each 20 pixels square, and the snake moves one whole cell at a time.

Work in cells and turn them into pixels only to draw. Cell (col, row) starts at pixel (col * 20, row * 20). Drawing each cell 2 pixels smaller, 1 pixel in from each side, leaves a thin gap between neighbours so you can see the snake's segments.

def draw_cell(cell, color):
    col, row = cell
    pygame.draw.rect(screen, color, (col * CELL + 1, row * CELL + 1, CELL - 2, CELL - 2))

col, row = cell unpacks the tuple into two variables. Keep the numbers in constants like CELL, COLS and ROWS: the code says what they mean, and changing one changes the whole game.

Challenge

Easy

Above the loop, write draw_cell(cell, color), which draws one cell 1 pixel in from each side, as above.
Set head = (5, 9).
After the fill, draw the head with draw_cell(head, (180, 255, 160)).

Try it yourself

import pygame

CELL = 20
COLS, ROWS = 24, 18

pygame.init()
screen = pygame.display.set_mode((COLS * CELL, ROWS * CELL))
pygame.display.set_caption("Snake")
clock = pygame.time.Clock()

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False

    screen.fill((30, 30, 46))
    pygame.display.flip()
    clock.tick(10)

pygame.quit()