Pong in 30 Lines

size(400,400)
speed(40)

ball_diameter = 20
paddle_size = 75
v_x, v_y = (3, 4)
p_x, p_y = (10, 10)
bounce = 1.2
points = []
computer = WIDTH / 2
compuspeed = 10

def draw():
    global v_x, v_y, p_x, p_y, points, bounce, computer, compuspeed
    
    if not -ball_diameter < p_y < HEIGHT + ball_diameter:
        text("Game Over", WIDTH/2, HEIGHT/2)
        if p_y < 0: text("You win!", WIDTH/2, HEIGHT/2+20)
        else:       text("Computer wins", WIDTH/2, HEIGHT/2-20)
        return

    paddle_left = min(max(MOUSEX, 0), WIDTH-paddle_size)
    ny = p_y + v_y
    nx = p_x + v_x
    
    if nx + (ball_diameter/2) > computer + paddle_size: computer += compuspeed
    elif p_x + v_x < computer:                          computer -= compuspeed
    rect(computer, 0, paddle_size, 4, roundness=2)

    if ny + ball_diameter > HEIGHT and v_y > 0 \
    and paddle_left < nx + (ball_diameter / 2) < paddle_left + paddle_size:
        v_y = -v_y * bounce
        v_x = (nx - paddle_left - (paddle_size / 2)) * .25
        ny = HEIGHT - ball_diameter
    if ny < 0 and v_y < 0 \
    and computer < nx + (ball_diameter / 2) < computer + paddle_size:
        v_y = -v_y * bounce
        v_x = (nx - computer - (paddle_size / 2)) * .25
        ny = 0
    elif nx + ball_diameter > WIDTH or nx < 0:
        v_x = -v_x
        
    mx = max(0, min(MOUSEX, WIDTH - paddle_size))
    rect(mx, HEIGHT-4, paddle_size, 4, roundness=2)

    p_x = nx
    p_y = ny
    oval(p_x, p_y, ball_diameter, ball_diameter)