A Body List

Lesson 23 of 40 in Coddy's Make Games with Pygame course.

The snake is a list of cells, head first:

body = [(5, 9), (4, 9), (3, 9)]

To move, add the new head at the front and remove the last cell. Every middle cell stays where it is, so the body follows the head:

x = body[0][0] + direction[0]
y = body[0][1] + direction[1]
body.insert(0, (x, y))
body.pop()

body.insert(0, item) puts the item at index 0. body.pop() removes the last item. body[0] is the head and body[1:] is the rest.

Draw the rest in a darker green and the head last, so it is on top.

Challenge

Easy

Replace head = (5, 9) with body = [(5, 9), (4, 9), (3, 9)].
Each frame, work out the new head (x, y) from body[0], insert it at the front and pop the tail.
Draw each cell of body[1:] in (120, 220, 120), then body[0] in (180, 255, 160).

Try it yourself

import pygame

CELL = 20
COLS, ROWS = 24, 18
TURNS = {
    pygame.K_LEFT: (-1, 0),
    pygame.K_RIGHT: (1, 0),
    pygame.K_UP: (0, -1),
    pygame.K_DOWN: (0, 1),
}

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


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


head = (5, 9)
direction = (1, 0)

running = True
while running:
    moving = direction
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN and event.key in TURNS:
            turn = TURNS[event.key]
            if turn != (-moving[0], -moving[1]):
                direction = turn

    head = (head[0] + direction[0], head[1] + direction[1])

    screen.fill((30, 30, 46))
    draw_cell(head, (180, 255, 160))
    pygame.display.flip()
    clock.tick(10)

pygame.quit()