3. Space Invaders
Space Invaders https://www.mfitzp.com/article/microbit-space-invaders/
Press A to fire, press B to bomb 3 if bombs are available
Tilt to move side to side
from microbit import *
import random
MIN_COORD, MAX_COORD = 0, 4 # Range of valid coordinates for the display.
MAX_MISSILES = 5 # Number of missiles player can have on screen at once.
DIFFICULTY_INCREASE = 0.25 # Increase in difficulty between waves.
ALIEN_START_POSITIONS = [
# Each row is a unique start pattern, defined as tuples of x,y coordinates.
[(1, 0), (2, 0), (3, 0), (1, 1), (2, 1), (3, 1)],
[(0, 0), (1, 0), (2, 0), (3, 0), (4, 0), (2, 1)],
[(1, 0), (2, 0), (3, 0), (0, 1), (2, 1), (4, 1)],
[(1, 0), (2, 0), (3, 0), (1, 1), (3, 1), (2, 2)],
]
def wait_for_button():
""" Wait for either button to be pressed. """"
while not (button_a.was_pressed() or button_b.was_pressed()):
sleep(1)
def move(sprite, x, y):
""" Move the given sprite by the given x & y amounts. """
return sprite[0] + x, sprite[1] + y
def in_bounds(pos):
""" Return True if the position is within the valid screen coordinates. """
if pos[0] < MIN_COORD or pos[0] > MAX_COORD:
return False
if pos[1] < MIN_COORD or pos[1] > MAX_COORD:
return False
return True
class Game:
""" Game class holds the current game state. """
def game_reset(self):
# Initial values
self.x = 2 # Player x coordinate start (middle).
self.xf = 2.0 # x coordinate float, allows us to use tilt for move speed.
self.missiles = [] # Active missles on screen.
self.aliens = [] # Active aliens on screen.
self.alien_velocity_x = 1 # Horizontal speed of aliens.
self.bombs = 3 # Number of bombs the player has.
self.active_bomb = 0 # Countdown timer for the current active bomb.
self.score = 0 # Player score.
self.tick = 0 # Game loop tick.
self.level = 0 # Current game level.
self.difficulty = 20 # Is in reverse, decrement to increase.
def handle_input(self):
self.tick += 1
acc_x = accelerometer.get_x()
# Use the accelerometer / 512 so the player can move x at speed by tilting more.
if acc_x < 0:
self.xf += acc_x / 512
if acc_x > 0:
self.xf += acc_x / 512
# Constrain to the screen dimensions.
if self.xf > MAX_COORD:
self.xf = MAX_COORD
if self.xf < MIN_COORD:
self.xf = MIN_COORD
self.x = int(self.xf)
if button_a.was_pressed():
# Add missile, at players current x position.
self.missiles.append((self.x, 4))
if button_b.was_pressed() and self.bombs:
# Fire bomb. Flash + remove half the aliens.
# randint(0,1) will be 50% 1, 50% 0 ..if 0 (False) alien will be skipped.
self.aliens = [alien for alien in self.aliens if random.randint(0, 1)]
self.active_bomb = 3 # Reduces 1 per tick. Screen at 3 * bright.
self.bombs -= 1
def add_aliens(self):
# We need to copy, or we'll me modifying the original lists.
alien_position = self.level % len(ALIEN_START_POSITIONS)
self.aliens = ALIEN_START_POSITIONS[alien_position].copy()
self.tick = 0
def advance_aliens(self):
""" If aliens have reached the screen edge, advance them all downwards. """
for alien in self.aliens:
if (self.alien_velocity_x == -1 and alien[0] == MIN_COORD) or (
self.alien_velocity_x == +1 and alien[0] == MAX_COORD
):
# If any aliens are at the far edge, increment y, and reverse.
self.alien_velocity_x = -self.alien_velocity_x
self.aliens = [move(alien, 0, 1) for alien in self.aliens]
# This can happen if detached alien slips past bottom.
self.aliens = [alien for alien in self.aliens if in_bounds(alien)]
return True # No other move this time.
def aliens_can_move(self):
if self.tick > self.difficulty:
self.tick = 0
return True
def move_aliens(self):
# Move aliens horizontally.
self.aliens = [move(alien, self.alien_velocity_x, 0) for alien in self.aliens]
def move_missiles(self):
# Advance positions of missiles (upwards)
self.missiles = [move(missile, 0, -1) for missile in self.missiles]
self.missiles = [missile for missile in self.missiles if in_bounds(missile)]
def check_collisions(self):
for missile in self.missiles[:]: # Iterate a copy.
if missile in self.aliens:
# Since we store by coordinates, we can remove using the missile coords.
self.aliens.remove(missile)
self.missiles.remove(missile)
self.score += 1
if not self.aliens:
# Wave complete? Increase difficulty (decrement) and add new aliens.
self.difficulty -= DIFFICULTY_INCREASE
self.level += 1
self.bombs += 1
self.add_aliens()
def draw(self):
display.clear()
if self.active_bomb:
# Bomb is drawn as an overlay of gradually decaying light.
for dx in range(MAX_COORD + 1):
for dy in range(MAX_COORD + 1):
display.set_pixel(dx, dy, self.active_bomb * 3)
# Decrement so next draw is fainter.
self.active_bomb -= 1
# Draw all the aliens.
for pos in self.aliens:
display.set_pixel(pos[0], pos[1], 9)
# Draw all the current player missles.
for pos in self.missiles:
display.set_pixel(pos[0], pos[1], 5)
# Draw the players spaceship.
display.set_pixel(self.x, 4, 9)
def game_over(self):
return (self.x, 4) in self.aliens
game = Game() # Create our game object.
while True:
display.show(Image.TARGET)
wait_for_button()
game.game_reset() # Reset the game state.
game.add_aliens()
# Main loop
while not game.game_over():
game.handle_input()
if game.aliens_can_move():
if not game.advance_aliens():
game.move_aliens()
game.move_missiles()
game.draw()
game.check_collisions()
sleep(100)
display.show(Image.ANGRY)
sleep(1000)
display.scroll(game.score)
Tasks
Adjust the code to allow a new game if A or B is pressed.