Review & Extension

Review the completed game by filling in the missing pieces of the final integration.

# ── Full game integration ──
class Game:
    def __init__(self):
        self.snake  = Snake(▢1, 7)
        self.food   = self._spawn_food()
        self.score  = ▢2
        self.running = ▢3

    def _spawn_food(self):
        while True:
            pos = (random.randint(0, GRID_COLS-1),
                   random.randint(0, ▢4-1))
            if pos not in self.snake.body_set:
                return ▢5

    def update(self):
        self.snake.▢6()
        if not self.snake.is_alive():
            self.running = ▢7
            return
        if self.snake.body[0] == self.food:
            self.snake.grew = ▢8
            self.score += 1
            self.food = self.▢9()

    def run(self):
        clock = pygame.time.Clock()
        while self.running:
            for event in pygame.event.get():
                if event.type == pygame.QUIT:
                    self.running = False
                if event.type == pygame.KEYDOWN:
                    key_map = {pygame.K_UP:"UP", pygame.K_DOWN:"DOWN",
                               pygame.K_LEFT:"LEFT", pygame.K_RIGHT:"RIGHT"}
                    if event.key in key_map:
                        self.snake.▢10(key_map[event.key])
            self.update()
            self.▢11()
            clock.tick(SNAKE_SPEED)
        pygame.quit()

The integrated Game class below has 3 bugs. Type the corrected line for each.

class Game:
    def __init__(self):
        self.snake   = Snake(10, 7)
        self.food    = self._spawn_food()
        self.running = True

    def update(self):
        self.snake.move()
        if self.snake.body[0] == food:       # Bug 1 – missing self.
            self.snake.grew = True
        if not self.snake.is_alive():
            running = False                  # Bug 2 – missing self.

    def draw(self, screen):
        screen.fill(BG)
        for i,(cx,cy) in enumerate(self.snake):   # Bug 3 – wrong iterable
            colour = (0,180,60) if i==0 else GREEN
            pygame.draw.rect(screen, colour,
                pygame.Rect(cx*CELL_SIZE,cy*CELL_SIZE,CELL_SIZE-2,CELL_SIZE-2), border_radius=4)

Write **unit tests** for three functions: `Snake.turn()` (can't reverse), `Snake.is_alive()` (boundary), and `Game._spawn_food()` (not on snake). Use Python's `assert` statement.

# No pygame display needed for unit tests
import pygame
pygame.init()
pygame.display.set_mode((400,300))   # minimal surface

snake = Snake(10, 7)

# Test 1: Snake cannot reverse direction
snake.direction = "RIGHT"
snake.turn("LEFT")   # should be blocked
assert snake.direction == {{"RIGHT"}}, "Reversal guard failed"

# Test 2: Snake.is_alive() returns False for out-of-bounds head
snake.body[0] = (-1, 7)
assert snake.is_alive() == {{False}}, "Boundary check failed"

# Test 3: Food does not spawn on the snake
game = Game()
for _ in range(50):
    food = game._spawn_food()
    assert food not in snake.body_set, "Food spawned on snake!"

print("All tests passed!")

**Final Challenge:** Add one meaningful extension to the complete game. Ideas: multi-food mode, speed ramp-up, obstacle walls, two-player mode, or a simple sprite for the head. Paste the code for your chosen feature and explain how it fits into the class structure.

Answer each prompt thoughtfully. There are no right or wrong answers — this is your own reflection.