Learn to Code a Snake Game with CircuitPython on Gamebuino META

snake.py

# ----------------------------------------------------------
# Learn to Code a Snake Game with Python
# Gamebuino Academy Workshop
# https://gamebuino.com/academy/workshop/learn-to-code-a-snake-game-with-python
# ----------------------------------------------------------
# This game is based on the CircuitPython environment, which
# is an implementation of the Python language specific to
# microcontrollers. CircuitPython runs on the SAMD21G18
# architecture of the Gamebuino META.
# ----------------------------------------------------------
# Author: Steph
# Date: April 2019
# ----------------------------------------------------------

from gamebuino_meta import waitForUpdate, display, color, buttons
from random import randint

# ----------------------------------------------------------
# Global variables
# ----------------------------------------------------------

SCREEN_WIDTH  = 80
SCREEN_HEIGHT = 64
SNAKE_SIZE    = 2
SNAKE_LENGTH  = 4
SNAKE_EXTENT  = 2
COLS          = (SCREEN_WIDTH  - 4) // SNAKE_SIZE
ROWS          = (SCREEN_HEIGHT - 4) // SNAKE_SIZE
OX            = (SCREEN_WIDTH  - COLS * SNAKE_SIZE) // 2
OY            = (SCREEN_HEIGHT - ROWS * SNAKE_SIZE) // 2
COLOR_BG      = 0x69c0
COLOR_WALL    = 0xed40
COLOR_SNAKE   = 0xfd40
COLOR_APPLE   = 0x07f0
COLOR_SCORE   = 0xffff
COLOR_LOST_BG = 0x8800
COLOR_LOST_FG = 0xffff
MODE_START    = 0
MODE_READY    = 1
MODE_PLAY     = 2
MODE_LOST     = 3

# ----------------------------------------------------------
# Game management
# ----------------------------------------------------------

def tick():
    if not game['refresh']:
        clearSnakeTail()
    
    if game['mode'] == MODE_START:
        resetSnake()
        spawnApple()
        game['mode'] = MODE_READY
        game['score'] = 0
        game['time']  = 0
    elif game['mode'] == MODE_READY:
        game['refresh'] = False
        handleButtons()
        moveSnake()
        if snakeHasMoved():
            game['mode'] = MODE_PLAY
    elif game['mode'] == MODE_PLAY:
        handleButtons()
        moveSnake()
        if game['refresh']:
            game['refresh'] = False
        if didSnakeEatApple():
            game['score'] += 1
            game['refresh'] = True
            extendSnakeTail()
            spawnApple()
        if didSnakeBiteItsTail() or didSnakeHitTheWall():
            game['mode'] = MODE_LOST
            game['refresh'] = True
    else:
        handleButtons()

    draw()
    game['time'] += 1

def spawnApple():
    apple['x'] = randint(0, COLS - 1)
    apple['y'] = randint(0, ROWS - 1)

def handleButtons():
    if buttons.pressed(buttons.LEFT):
        dirSnake(-1, 0)
    elif buttons.pressed(buttons.RIGHT):
        dirSnake(1, 0)
    elif buttons.pressed(buttons.UP):
        dirSnake(0, -1)
    elif buttons.pressed(buttons.DOWN):
        dirSnake(0, 1)
    elif game['mode'] == MODE_LOST and buttons.pressed(buttons.A):
        game['mode'] = MODE_START

# ----------------------------------------------------------
# Snake management
# ----------------------------------------------------------

def resetSnake():
    x = COLS // 2
    y = ROWS // 2
    snake['x'] = []
    snake['y'] = []
    for _ in range(SNAKE_LENGTH):
        snake['x'].append(x)
        snake['y'].append(y)
    snake['head'] = SNAKE_LENGTH - 1
    snake['len']  = SNAKE_LENGTH
    snake['vx'] = 0
    snake['vy'] = 0

def dirSnake(dx, dy):
    snake['vx'] = dx
    snake['vy'] = dy

def moveSnake():
    h = snake['head']
    x = snake['x'][h]
    y = snake['y'][h]
    h = (h + 1) % snake['len']
    snake['x'][h] = x + snake['vx']
    snake['y'][h] = y + snake['vy']
    snake['head'] = h

def snakeHasMoved():
    return snake['vx'] or snake['vy']

def didSnakeEatApple():
    h = snake['head']
    return snake['x'][h] == apple['x'] and snake['y'][h] == apple['y']

def extendSnakeTail():
    i = snake['head']
    n = snake['len']
    i = (i + 1) % n
    x = snake['x'][i]
    y = snake['y'][i]
    for _ in range(SNAKE_EXTENT):
        snake['x'].insert(i, x)
        snake['y'].insert(i, y)
    snake['len'] += SNAKE_EXTENT

def didSnakeBiteItsTail():
    h = snake['head']
    n = snake['len']
    x = snake['x'][h]
    y = snake['y'][h]
    i = (h + 1) % n
    for _ in range(n-1):
        if snake['x'][i] == x and snake['y'][i] == y:
            return True
        i = (i + 1) % n
    return False

def didSnakeHitTheWall():
    h = snake['head']
    x = snake['x'][h]
    y = snake['y'][h]
    return x < 0 or x == COLS or y < 0 or y == ROWS

# ----------------------------------------------------------
# Graphic display
# ----------------------------------------------------------

def draw():
    if game['refresh']:
        clearScreen()
        drawWalls()
        drawSnake()
    else:
        drawSnakeHead()
    drawScore()
    drawApple()

def clearScreen():
    color = COLOR_LOST_BG if game['mode'] == MODE_LOST else COLOR_BG
    display.clear(color)

def drawWalls():
    color = COLOR_LOST_FG if game['mode'] == MODE_LOST else COLOR_WALL
    display.setColor(color)
    display.drawRect(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT)

def drawSnake():
    isTimeToBlink = game['time'] % 4 < 2
    color = COLOR_LOST_FG if game['mode'] == MODE_LOST and isTimeToBlink else COLOR_SNAKE
    n = snake['len']
    for i in range(n):
        drawDot(snake['x'][i], snake['y'][i], color)

def drawSnakeHead():
    h = snake['head']
    drawDot(snake['x'][h], snake['y'][h], COLOR_SNAKE)

def clearSnakeTail():
    h = snake['head']
    n = snake['len']
    t = (h + 1) % n
    drawDot(snake['x'][t], snake['y'][t], COLOR_BG)

def drawScore():
    display.setColor(COLOR_SCORE)
    display.print(2, 2, game['score'])

def drawApple():
    drawDot(apple['x'], apple['y'], COLOR_APPLE)

def drawDot(x, y, color):
    display.setColor(color)
    display.fillRect(OX + x * SNAKE_SIZE, OY + y * SNAKE_SIZE, SNAKE_SIZE, SNAKE_SIZE)

# ----------------------------------------------------------
# Initialization
# ----------------------------------------------------------

game = {
    'mode':    MODE_START,
    'score':   0,
    'time':    0,
    'refresh': True
}

snake = {
    'x':    [],
    'y':    [],
    'head': 0,
    'len':  0,
    'vx':   0,
    'vy':   0
}

apple = { 'x': 0, 'y': 0 }

# ----------------------------------------------------------
# Main loop
# ----------------------------------------------------------

while True:
    waitForUpdate()
    tick()