Pong

# Implementation of classic arcade game Pong

import simplegui
import random

# initialize globals - pos and vel encode vertical info for paddles
WIDTH = 600
HEIGHT = 400
BALL_RADIUS = 20
PAD_WIDTH = 8
PAD_HEIGHT = 80
HALF_PAD_WIDTH = PAD_WIDTH / 2
HALF_PAD_HEIGHT = PAD_HEIGHT / 2
LEFT = False
RIGHT = True

# initialize ball_pos and ball_vel for new bal in middle of table
# if direction is RIGHT, the ball's velocity is upper right, else upper left
def spawn_ball(direction):
    global ball_pos, ball_vel # these are vectors stored as lists
    ball_pos = [WIDTH/2, HEIGHT/2]
    if direction:
        ball_vel = [- (random.randrange(120, 240)) / 60.0, - (random.randrange(60, 180)) / 60.0]
    else:
        ball_vel = [random.randrange(120, 240) / 60.0, - (random.randrange(60, 180)) / 60.0]

# define event handlers
def new_game():
    global pad1_pos, pad2_pos, pad1_vel, pad2_vel, speed  # these are numbers
    global score1, score2  # these are ints
    pad1_pos = HEIGHT / 2 - HALF_PAD_HEIGHT
    pad2_pos = HEIGHT / 2 - HALF_PAD_HEIGHT
    pad1_vel = 0
    pad2_vel = 0
    score1 = 0
    score2 = 0
    spawn_ball(random.randrange(2)) # Use random to choose initial direction

def draw(canvas):
    global score1, score2, pad1_pos, pad2_pos, ball_pos, ball_vel

    # draw scores
    canvas.draw_text(str(score1), [WIDTH - WIDTH / 4, HEIGHT/3], 40, 'Yellow')
    canvas.draw_text(str(score2), [WIDTH / 4, HEIGHT/3], 40, 'Yellow')

    # draw mid line and gutters
    canvas.draw_line([WIDTH / 2, 0],[WIDTH / 2, HEIGHT], 1, "Orange")
    canvas.draw_line([PAD_WIDTH, 0],[PAD_WIDTH, HEIGHT], 1, "Orange")
    canvas.draw_line([WIDTH - PAD_WIDTH, 0],[WIDTH - PAD_WIDTH, HEIGHT], 1, "Orange")

    # update ball
    if ball_pos[0] <= PAD_WIDTH + BALL_RADIUS:
        if (pad1_pos <= ball_pos[1]) and (pad1_pos + PAD_HEIGHT >= ball_pos[1]):
            ball_vel[0] = - ball_vel[0]
            ball_vel[0] =  ball_vel[0] + ball_vel[0]/ 10.0
            ball_vel[1] = ball_vel[1] +  ball_vel[1]/ 10.0
        else:
            spawn_ball(0)
            score1 += 1
    elif ball_pos[0] >= WIDTH - PAD_WIDTH - BALL_RADIUS:
        if (pad2_pos <= ball_pos[1]) and (pad2_pos + PAD_HEIGHT >= ball_pos[1]):
            ball_vel[0] = - ball_vel[0]
            ball_vel[0] = ball_vel[0] +  ball_vel[0]/ 10.0
            ball_vel[1] = ball_vel[1] +  ball_vel[1]/ 10.0
        else:
            spawn_ball(1)
            score2 += 1
    elif (ball_pos[1] <= 0 + BALL_RADIUS) or (ball_pos[1] >= HEIGHT - BALL_RADIUS):
        ball_vel[1] = - ball_vel[1]
    ball_pos[0] += ball_vel[0]
    ball_pos[1] += ball_vel[1]

    # draw ball
    canvas.draw_circle(ball_pos, BALL_RADIUS, 1, 'Navy', 'Navy')

    # update paddle's vertical position, keep paddle on the screen
    if 0 <= pad1_pos + pad1_vel <= HEIGHT - PAD_HEIGHT:
        pad1_pos += pad1_vel
    if 0 <= pad2_pos + pad2_vel <= HEIGHT - PAD_HEIGHT:
        pad2_pos += pad2_vel

    # draw paddles
    canvas.draw_line([HALF_PAD_WIDTH, pad1_pos], [HALF_PAD_WIDTH, pad1_pos + PAD_HEIGHT], PAD_WIDTH, 'Orange')
    canvas.draw_line([WIDTH - HALF_PAD_WIDTH, pad2_pos], [WIDTH - HALF_PAD_WIDTH, pad2_pos + PAD_HEIGHT], PAD_WIDTH, 'Orange')

# define key input
def keydown(key):
    global pad1_vel, pad2_vel
    speed = 10
    if key == simplegui.KEY_MAP['w']:
        pad1_vel -= speed
    elif key == simplegui.KEY_MAP['s']:
        pad1_vel += speed
    elif key == simplegui.KEY_MAP['up']:
        pad2_vel -= speed
    elif key == simplegui.KEY_MAP['down']:
        pad2_vel += speed

def keyup(key):
    global pad1_vel, pad2_vel
    speed = 10
    if key == simplegui.KEY_MAP['w']:
        pad1_vel += speed
    elif key == simplegui.KEY_MAP['s']:
        pad1_vel -= speed
    elif key == simplegui.KEY_MAP['up']:
        pad2_vel += speed
    elif key == simplegui.KEY_MAP['down']:
        pad2_vel -= speed

# create frame, register handlers
frame = simplegui.create_frame("Pong", WIDTH, HEIGHT)
frame.set_canvas_background('Olive')
frame.set_draw_handler(draw)
frame.set_keydown_handler(keydown)
frame.set_keyup_handler(keyup)
frame.add_button('Reset', new_game)

# start frame
new_game()
frame.start()