minimize use of "magic numbers"

[ASong5]

    self.hitbox = pygame.Rect(
        self.rect.x + self.image.get_width() / 7,
        self.rect.y + self.image.get_height() * (3 / 4),
        self.rect.width - 2 * (self.image.get_width() / 7),
        self.image.get_height() / 4,
    )

this is a prime example of magic numbers in the code; these numbers should be defined somewhere to impose some sort of meaning upon them + reduce code duplication